Restriction enzyme digestion and analysis

TheDNA samples were mixed with appropriate volumes of 6 X loading dye (0.25%bromophenol blue and 0.25% xylene cyanol and 30% glycerol in water) and subjectedto electrophoresis through 0.8 to 1 % agarose gel in TAE buffer. The gel was stained in1 μg/ml ethidium bromide solution for 15-min at room temperature and visualised byfluorescence under UV-light in a UV-transilluminator

Agarose gel electrophoresis

werethen recovered by centrifugation at 12,000 rpm for 30-min. The pellet was washed oncewith 70% ethanol, air-dried and re-suspended in 100 μl of TE-buffer. It was treatedwith RNase at a concentration of 20 μg/ml by incubating at 37ºC for 1-hr. It was furtherextracted with an equal volume of phenol:chloroform mixture followed bychloroform:isoamyl alcohol (24:1) mixture. After centrifugation, the clear supernatantwas used for recovering the nucleic acids. The nucleic acids were precipitated with 200μl of alcohol in presence of 0.3 M sodium acetate (Sambrook and Russell, 2001). In casewhere high purity plasmid preparations are required (DNA sequencing) the plasmidisolation was carried out with the commercially available kits following themanufacturer’s instruction. Plasmids were observed on 1% agarose gel

1.5 ml of stationary phase culture wascentrifuged and cell pellet was re-suspended in 567 μl of TE buffer. To this 30 μl of10% SDS, and 3 μl of proteinase K (20 mg/ml) were added in that order and the cellsuspension was mixed and incubated at 37ºC for 1-hr. When the suspension was clear, 100 μl of 5 M NaCl was added and thoroughly mixed followed by the addition of 80 μlCTAB/NaCl (10% cetyl trimethyl ammonium bromide in 7 M NaCl). The suspensionwas incubated at 65ºC for 10-min, brought to room temperature and extracted with anequal volume (780 μl) of chloroform isoamyl alcohol (24:1), and aqueous phasetransferred to fresh tube. The aqueous phase was further extracted successively, firstwith phenol:chloroform:isoamyl alcohol (25:24:1) and then with chloroform isoamylalcohol (24:1). DNA was precipitated fromthe clear supernatant by the addition of 0.6volumes of iso-propanol. The chromosomal DNA was either spooled out or pelleted atthis stage and washed with 70% ethanol air dried and dissolved in 100 μl of TE-buffer

Isolation of chromosomal DNA

1.5 ml of cells from an overnight culture waspelleted by centrifuging in cold (4ºC) for10-min at 6000 rpm. The cells were re-suspended in 200 μl solution I (50 mM glucose; 25 mM Tris-Cl, pH-8; 10 mM EDTA, pH-8) with vortexing. 400 μl of freshly preparedsolution II (0.2% NaOH, 1% SDS) was added and mixed by gently inverting the tubes.Subsequently, 300 μl of solution III (prepared by mixing 60 ml of 5 M CH3COOK,11.5 ml glacial acetic acid, 28 ml water) was added and the tubes were invertedrepeatedly and gently for homogeneous mixing followed by incubation for 5-min onice. After centrifuging at 12,000 rpm for 15-min, supernatant wasdecanted into a freshtube, an equal volume of iso-propanol was added, the precipitated nucleic acids

Isolation of plasmid DNA

Recombinant DNA techniques

The colonies to be tested were streaked on the surface of minimal A-glucose plates containing either 0.4-0.7 M NaCl with 1 mM glycine betaine, and incubated at 37oC. NaCl-tolerant strains grew toform single colonies in 36-60 hrs whereas NaCl-sensitive ones did not. As controls, MC4100 (WT) and other previously identified NaCl sensitive mutants were streakedfor comparison

NaCl-sensitivity testing

Competent cells for high efficiency transformations were prepared by a method ofInoue et al. (1990) with few modifications. An overnight culture of the strain (routinelyDH5α) was sub-cultured into fresh sterile LB-brothin 1:100 dilutions and grown at 18ºC to an A600of 0.55. The cells were harvested by centrifugation at 2500 rpm for 10-min at 4ºC. This was re-suspended in 0.4 volumes of INOUE buffer and incubated inice for 10 min. The cells were recovered by centrifugation at 2500 rpm at 4ºC for 10-min and finally re-suspended in 0.01 volume of the same buffer. Sterile DMSO wasadded to a final concentration of 7%. After incubating for 10-min in ice, the cells werealiquoted in 100 μl volumes, snap frozen in liquid nitrogen and stored at –70ºC

Preparation of high efficiency competent cells

the infection mixture was centrifuged, washed in 5 ml of citratebuffer and plated without phenotypic expression

To 2 ml of fresh overnight culture of recipient strain, 108pfu equivalent of phage lysatewas added and incubated at 37ºC without shaking for 15-min to facilitate phageadsorption. The un-adsorbed phage particles were removed by centrifugation at 4000rpm for 5-min and pellet of bacterial cells was re-suspended in 5 ml of LB-brothcontaining 20 mM sodium citrate to prevent further phage adsorption. This wasincubated for 30-min at 37ºC without shaking to allow the phenotypic expression of theantibiotic resistance gene. The mixture was then centrifuged, and the pellet was resuspendedin 0.3 ml citrate buffer. 100 μl aliquots were plated on appropriate antibioticcontaining plates supplemented with 2.5 mM sodium citrate. A control tube withoutaddition of P1 lysate was also processed in the same way. In the case of selection ofnutritional requirement,

Phage P1 transduction

For TEM, C. glabrata cells were digested with zymolyase 20T for 3 h at 30◦C, centrifuged at 1,000 g and washed with YPD medium. Cell fixation was performed as described for SEM and dehydrated samples were embedded in araldite 6005 resin. After complete polymerization at 80 ̊C for 72 h, ultra-thin (50-70 nm) sections were preparedwith a glass knife on Leica Ultra cut (UCT-GA-D/E-1/00)microtomeand mounted on copper grids. Aqueous uranyl acetate-stained and Reynolds lead citrate-counterstained samples were viewed under Hitachi H-7500 transmission electron microscope

Transmission electron microscopy

Cell wall β-glucan measurement was carried out as describedpreviously with some modifications(Kapteynet.al.,2001). Briefly, cell wall fractions were washed multiple times with 1 N NaCl. Washed cell walls were boiled twice in 50 mM Tris-HCl(pH 7.8) containing 2% SDS, 100 mM Na-EDTA and 40 mM β-mercaptoethanol for 5 min to remove non-covalently linked proteins and other contaminants. SDS-treated cell wall fraction was collected and rinsed thrice with water. For β-glucan isolation, cell wallswere extracted three times, each for 1 h, in 0.5 ml 3% NaOH at 75 ̊C and centrifuged at 1,200 g.All 3% NaOH supernatant fractions were saved for isolation of mannan as described below. 3% NaOH-extractable cell wall pelletwasneutralized twice in 100 mM Tris-HCl (pH 7.5) and once in 10 mM Tris-HCl (pH 7.5) and digested with 5 mg/ml zymolyase-20T in 10 mM Tris-HCl (pH 7.5) for 14-16 h at 37 ̊C. This treatment liberates approximately 90-95% glucose into the supernatant. Total glucan content in the cell wall was measured by estimating glucose from both the solubilised supernatant and zymolyase-20T insoluble pellet fractions with phenol-sulphuric acid carbohydrate estimation method using purified glucose as the standard

Total β-glucan estimation

Vacuole membraneswere isolatedwith slight modifications of Cabrera’s method(Cabrera et.al.,2008). Log-phase, YPD medium-grown cells wereinoculated in 1 lt YPDmedium to an initialOD600of 0.1. Cells were incubated at 30 ̊C with shaking at 200 rpm till the cell density reached to OD600of 0.8-1.0.Cells were harvested by centrifugation at 5,000 g and washed once with 30 ml 2% ice-cold glucose solution. Cells were incubated in 15 ml solution containingglycine-NaOH(50 mM; pH10)andDTT(2 mM) at 30 ̊C for 10 min. After incubation, cells were normalized to adensity of1000OD600and resuspendedin 15 ml spheroplasting buffer containing 10-15mg of zymolyase20T.Cells were incubated at 30 ̊C for 45-60 minor till the spheroplasting was completed.Spheroplasts werecollected by centrifugation at 4,500 rpmfor 5 minat 4 ̊C, washed gently with15 ml 1.2 M sorbitol solutionandresuspendedin 3.5 ml 15%ficoll solution made in PS buffercontaining 1X protease inhibitor cocktail. This suspension was homogenized on ice with 20-25 strokes in a loose-fitting Dounce homogenizer. Homogenate was transferred to an ice-cold,ultra-clear Beckman ultracentrifuge tube, overlaid witha gradient of3 ml 8%ficoll solution, 2.5 ml 4%ficoll solutionand 2.5 ml PS buffer lacking ficoll and centrifuged at 1,10,000g(30,000 rpm)for 90 minat 4 ̊Cin a pre-cooled Beckman ultracentrifuge with SW41-Ti swinging bucket rotor.Centrifugation was carried out with slow acceleration and deceleration settings.White creamy vacuole membrane layer wascollected from the interfaceof 0and4% ficoll gradientwithout mixing the layers.Total protein concentration in thevacuole fraction was estimated using BCAprotein assay kit as described earlier

Purified vacuole membrane isolation

Estimation of total glycogen in cells was performed asdescribed previously (Parrou et al., 1997) with slightmodifications.Briefly, YPD medium-grown C. glabratacells were harvested, washed once with 1 ml ice-cold waterandresuspendedin 250 μl sodium carbonate(0.25 M)solution. After incubation at95 ̊C for 4 hin water bath with occasional stirring, cell suspension was cooled and pH of the suspension was adjusted to 5.2 by adding 150 μl 1 M acetic acid. Tothis suspension,600 μl 0.2M sodium acetatewas added and cell suspension was incubated with 1-2 U/ml of α-amyloglucosidase from A.niger(Sigma #A7420)at 57 ̊C for overnight with constant agitation.Resultant glucose liberated by α-amyloglucosidase digestion was collected in the supernatant fraction and quantifiedby phenol-sulphuric acid methodof carbohydratedetermination.For quantification, commercially available purified glucose was used as a standard and total glycogen incells was expressed as μg/2 x 107cells tonormalizeagainstcell density

Estimation of glycogenlevels

dithiothreitol and1X protease inhibitor cocktail. Cell suspension was rapidly frozen at -80 ̊C,thawed and lysed with 0.5mm acid-washed glass beadsin a homogenizer (FastPrep®-24,MP Biomedicals)at maximum speed of 60 secfive times. Homogenate wasdiluted with 5mlTris-HCl (0.1M; pH 8.0)solutioncontaining 0.33M sucrose, 5mM EDTAand 2mM dithiothreitoland centrifuged at 1,000g for 3 minat 4 ̊C. Supernatant was collected and centrifuged again at 3,000g for 5 minat 4 ̊C to remove unbrokencells. The resulting supernatant was centrifuged at 19,000g for 45 minat 4 ̊C to obtain total membrane fraction. Total membrane pellet was resuspendedin 100μl membrane suspension buffer and stored at -80 ̊Ctill further use. Total protein concentration in the membrane fraction was estimated using BCAprotein assay kit (Thermo Scientific, US) with bovine serum albumin (BSA) used as astandard

Isolation of total membrane fractions from C. glabratastrains were carried out as described previously (Fernandes et al., 1998). Cells grown to log-phase under different environmental conditionswere harvested, washed and suspended to afinal density of 20 OD600cells in 1 ml solution containing100mM Tris (pH 10.7),5mM EDTA,2mM

Total membrane preparation

SDS-PAGEwas performed as described previously (Laemilli, 1970).10-40 μg protein samples were mixed with 4X SDS loading buffer and either incubated at 50 ̊C or 90 ̊C for 10 min. Denatured samples were loaded either on8%or 10%SDS-PAGEgel and run in Tris-Glycine-SDSgel running buffer at 70-100 Volts for 2-3 hin a Mini-PROTEAN®3electrophoresis unit(Bio-Rad).After electrophoresis,gels were either visualized by coomassie brilliant blue (CBB) stainingor processedfor western blotting as described below

Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis(SDS-PAGE)

hybridizations from biological replicates for each sample. Data was extracted with Feature Extraction software v 10.5 (Agilent) and normalizedwith GeneSpring GX v 11.0.1 (Agilent) software using the recommended Percentile shift Normalization to 75th percentile. Raw Data sets for this study are available at http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=

Log-phase wild-type and Cgyps1∆cells were grown in YNB and YNB-pH 2.0 medium. After 1 h incubation, yeast cells were collected, washed and were stored in RNAlater at -80°C. These frozen samples were sent to Genotypic Technology Ltd., Bangalore(http://www.genotypic.co.in) whichprovides services of global gene analysis on Agilent platform. A 8x15k GE array comprised of 60mer oligonucleotidesfor a total of C. glabrata5503 genes was used wherein average number of replicates for each probe was three. Labeling was done in single color and data is the average of two

Microarray analysis

.coliBW23473 electro-competent cell aliquots werethawed on ice and mixed with 1-2 lof plasmid DNA. Mixture was pulsed with the Gene Pulser®electroporation apparatus(Bio-Rad) at 1800 Volts with 25 μF and 200 Ωcurrentin a chilled0.1 cm electroporation cuvette(Bio-Rad). Immediately after successful pulsing, 1 ml LB medium was added to the cuvetteand suspension was transferred toa 1.5 ml sterile centrifuge tube. Cells wereincubated at 37°C for 1 hwith shaking and further plated onLB plates containing kanamycin(30μg/ml). Positive colonies were inoculated in LBliquid medium containing kanamycin(30μg/ml)for plasmid isolation

E.coliBW23473transformation by electroporationE

A single colony of E.coliBW23473strainfrom a freshly-streaked LBplate was inoculated in50ml LB medium. Culture was incubated overnight at 37°C with shaking at 200rpm. 25ml of the overnight-grown BW23473 culturewas transferred to500ml pre-warmed LB medium andincubated at 37°C till the OD600reached to 0.4. After incubation, cultureswere transferred to an ice-water bathandcentrifugeat 1,000g for 15 minat 4°C. Cells were washed twice with 500ml ice-coldwater, thrice with250ml ice-cold 10% glycerol solution and resuspendedin 1ml 10% glycerol solution. Cell suspension wasnormalized to final cell densityof 3x 1010cells/ml and dispensed in 50μl volume into sterile ice-cold microcentrifuge tubes. Aliquots weresnap frozen inliquid nitrogen and stored at -70 ̊C for further use

Electro-competentcell preparation

the disrupted gene, BLAST N of the sequences from rescued plasmids was performedagainstC. glabrataGenolevures database (http://www.genolevures.org/blast.html

Identification of disrupted locus in Tn7insertion mutants was carried out as described previously(Kaur et al.,2004). Disrupted locus in each mutant is physically marked with a mini Tn7 transposon derivative containing conditional origin of replication R6K(facilitates Tn7recovery), S. cerevisiae URA3and Klebsiella pneumoniae hphgene (confers resistance to hygromycin B)(Castaño et al.,2003). Briefly,genomic DNA was isolated fromovernight grown Tn7insertion mutants using spheroplast lysis method. After RNAse treatment, 10μgDNA was either digested withMfe1or SpeIrestriction enzymeas the Tn7 cassette lacks these enzyme sites. Followingovernight digestion, DNA wasprecipitated with 1ml ethanol and 1/10thvolume of 3 M sodium acetate (pH 5.2).DNApellet was washed twicewith ice-cold 70% ethanol, air driedand resuspendedin sterile MQ water. DNA was recircularized withT4 DNA ligase. Resultant circular plasmid contains the Tn7cassette flanked on either side by the gene,it has disruptedin the genome of C. glabrata.This circular plasmid DNA was transformedin E.coliBW23473 strain,which contains protein Π (the product of the pir gene)required by R6Korifor replication.Transformation of circularized DNA in E.coliBW23473 electrocompetent cells was performedas described below.Plasmids fromselected transformants were isolated and sequenced with outward primers from Tn7right and left ends to sequencethe disrupted gene fragment.For identification of

Tn7insertion mutant rescueand gene identification

C. glabrataTn7insertion mutantlibrary was screened for reduced growth in YNB-pH 2.0 medium. Thismutant library,composed of 9,134 Tn7insertion mutants, isarrayed in 96-well microtitre plates(Castaño et al.,2003). 2 μlof each mutant strain was inoculated in 120μl YNB medium and grown overnight at 30 ̊C in an incubator with constant shakingat 120 rpm. Overnight grown cultures were 120-folddiluted with 1X PBS in a 96 well block and transferred, using a 96-well pin replicator, to YNB and YNB-pH 2.0 medium. Plates were incubated at 30°C and mutant phenotypes were recorded after 3-4days.

Screening of C. glabrataTn7insertion mutants

and colony purified on CAA plate. 15% glycerol stocks were made for two independent transformants and stored at -80 ̊C

C. glabrataCgYPS7ORFwas cloned in a self-replicating pGRB2.2plasmidwhich contains C. glabrata CEN-ARS, S. cerevisiaeURA3gene, S. cerevisiaePGK1promoter and C. glabrataHIS3-3′ untranslated region. For cloning CgYPS7in pGRB2.2,CgYPS7ORF (1.764 kb) was PCR-amplified from the wild-type genomic DNA with high fidelity Platinum PfxDNA polymeraseusing primers carrying restriction sites for XbaIand XhoI. The1.764 kb amplifiedPCR product waspurified with QIAquick PCR purification kit (Qiagen # 28104),digested with XbaI and XhoI and cloned in the pGRB2.2plasmid at XbaI–XhoI sites in the multiple cloning site (MCS)region downstream of the PGK1promoter.Positiveclones were verified by PCR, sequencing and complementation analysesofCgyps7∆mutant. Yeast transformantsobtained by lithiumacetate methodwere selected on plates lacking uracil

Cloning of CgYPS7gene

stranded DNA. Final reaction volume was adjusted to 20 μl with DEPC-treated waterandamplificationreaction was carried out usingthese parameters: initial denaturation at 95 ̊C for 5 min followed by 40 cycles of denaturationat 95 ̊C for 30 sec, annealing at 55 ̊C-57 ̊C for 30 sec, elongation at 72 ̊C for 40 sec and final extension at 72 ̊C for 10 min. Transcript levelswerequantified with an end-point value known as Ct (cycle threshold). The Ctdefines the number of PCR cycles required forthe fluorescent signal of SYBR green dye to cross more than the background level. The Ctvalue isinversely proportional to the amount of nucleic acid product. Ctvalues were obtained during exponential phase of amplification and used forcalculation of relative-fold change in gene expression after normalization to Ctvalues ofeither housekeeping gene ACT1 (gene encoding actin)orTDH3 (gene encoding Gapdh)with the help of the following formula. Fold change in expression = 2-∆∆Ct∆∆Ct= ∆Cttreated -∆Ctuntreated∆Cttreated = Ctvalue forgene of interest under test/treatedcondition -Ctvalue forinternal controlgene(ACT1/TDH3) under test/treatedcondition∆Ctuntreated = Ctvalue forgene of interest under untreatedcondition -Ctvalue forinternal control (ACT1/TDH3)gene under untreatedcondition

Todeterminethe expression level of a specific gene, quantitative real-time polymerase chain reaction (qRT-PCR/qPCR)was performed oncDNA usinggene specific primers. Primers for qPCR weredesigned in such a way so as to get amplification products in a size range of 150 to 300 bp. Optimalprimer and cDNA concentrationswere standardized and qPCR was performed in ABI Prism 7000/7500 Real time PCR Machine (Applied Biosystems). Briefly, 0.4 μl cDNA was mixed with 0.1 to 0.2 picomolesof gene specific forward and reverse primers and 10 μl 2X MESA GREEN qPCR™Mastermix Plus containing SYBR green dye (Eurogentec) in awell of a96-well PCR plate (Axygen). SYBR green is a dye that specifically binds to double

Quantitative real-time polymerase chain reaction (qRT-PCR)

1 μg good quality RNA was treated with DNase I (amplification grade, Invitrogen) to remove DNA contamination and used for complementary DNA (cDNA) synthesis using reverse transcriptase enzyme and oligo-dT primers.SuperScript®III First-Strand Synthesis System (Invitrogen) was used to carry out cDNA synthesis reaction according to the manufacturer’s instructions. cDNA was stored at -20 ̊C

Complementary DNA (cDNA) synthesis

autoclavable plastic items to removeRNase contamination. RNA was isolated from C. glabratacells using hot phenol extraction strategy.Log-phase cells well harvested at 5,000 g for 5 min at 4 ̊C, resuspended in 1 ml ice-cold DEPCwater and transferred to a 2 ml microcentrifuge tube. Cells were spun down at 6,000 g for 3 min at 4 ̊C and resuspended in 350μl AEsolution. 50 μlSDS and 400 μl acid phenol wereadded tothe above tubeand mixed well by vortexing. Tubes were incubated at 65 ̊C for 15minwith continuousmixing. After incubation, tubes were kept on ice for 5 min and centrifuged at 12,000 rpm for 5 min at 4 ̊C. Aqueous phase was collected and re-extracted with an equal volume of cholroform. Total RNA was precipitated at -20 ̊C with1/10thvolume of 3 M sodium acetate (pH 5.2) and 2.5 volume of ice-cold 100% ethanol and collected by centrifugation at 12,000 rpm for 5 min at 4 ̊C. RNA pellet was washed with ice-cold 70% ethanol and resuspendedin 100 μl commercially available DEPC-treated water (Sigma # 95284). RNA concentration was measured byrecordingabsorbance at 260 nm. Purity of RNA sample was checked by A260nm/A280nmratio where ratio of >1.8 was considered as good quality RNA. RNA integrity was checked by gel electrophoresis on 8% agarose gel made in DEPC-treated TAE buffer

All solutions were made in RNase free diethylpyrocarbonate(DEPC)water. Microcentrifuge tubes and tips employed for RNA workwere autoclaved twice and kept at 70 ̊C for overnight before use. RNaseZap®(Ambion) was sprayed on non-

Total RNA isolation

Themethod was used for isolation of good quality genomic DNA that wasused to map Tn7insertionin C. glabratamutants.Briefly,10 mlsaturated yeast culturewasharvested, resuspendedin 1 ml sterile water and transferred toa2 ml microcentrifuge tube. Cells were pelleteddown by centrifugation at 4,000 rpm for 5 min. Supernatant was discarded and the pellet was resuspendedin 500 μl freshly prepared solutioncontaining100mM EDTAand 5% β-mercaptoethanol andincubated at 42 ̊C for 10 min. After incubation,cells were spun down at 5,000 rpm for 1 minand resuspendedin 500μl freshly-prepared BufferB. One tip full of lyticase(Sigma # L4025) was added and cellsuspension was incubated at 37 ̊C for 1 h. Following incubation,cell suspension was spun down at 6,000 rpm to recover spheroplasts.Spheroplasts weregently resuspendedin 500μl BufferCand DNA was twice extracted with 500μl phenol:chloroform:isoamyl alcohol (25:24:1)solution.Aqueous layer was collected in a new 2ml microcentrifuge tube and DNA was precipitated with 1ml ethanol and 1/10thvolume of 3M sodium acetate (pH 5.2)by centrifugation at 13,000 rpm for 5 min. Pellet was resuspendedin 200 μl TE containing 0.3 μl of RNase Cocktail™and incubated at 37 ̊C for 30 min.After incubation, 300 μl additional TE was added and DNAwas re-precipitated withethanol and 3 M sodium acetateas described above. Pellet was washed with 70% ethanol anddried under air. DNA pellet was finally suspended in 100 μl TE and stored at -20 ̊C

Protocol III(Spheroplast lysis method

phenol:chloroform:isoamyl alcohol (25:24:1)was added to the tube and mixed thoroughly.Aqueous phase was collected after centrifugationat 12,000 rpm for 3 minand was transferred toanew 2 ml microcentrifuge tube.1 ml absoluteethanol was added to the aqueous phase and DNA was precipitated by centrifugation at 12,000 rpm for 8 minat 4 ̊C.DNA pellet was washed with chilled 70%ethanol and dried under air. DNA pellet was resuspendedin 50 μl TE containing 0.3 μl of RNase Cocktail™(Ambion®# AM2286)and incubated at 50 ̊C for 20 min. 200 μl additional TE was added to the above suspension and DNA was stored at -20 ̊C

In this method of genomic DNA extraction,yeast cells werelysed by mechanical disruption with glass beads. Briefly, yeast cells were harvested after overnight growth in YPD medium, resuspendedin 500 μl waterand transferred toa2 ml microcentrifuge tube.Cells were pelleteddown at 10,000rpm for 1 min. Resulting supernatant was discarded and the pellet was resuspendedin 500 μl Buffer A. The tube was incubated at 65 ̊C for 15 min. After incubation, 500 μl ofphenol:chloroform:isoamyl alcohol (25:24:1) and 0.5 gm of acid-washed glass beads (Sigma # G8772) were addedto the tube. Cells were lysed by three cycles of high speed vortexing withintermittent ice breaksfor 45 secand pelleteddown at 12,000 rpm for 3 minat 4 ̊C.Uppermost aqueous phase was transferred to a 2 ml microcentrifuge tube,500 μl of

Protocol II (Glass bead lysis method)

This quick extraction method was used to isolate genomic DNA which was used as templateto amplify gene of interestor toverify the knock-out. C. glabratacells were grownovernight to saturation in 10 mlYPD medium at 30 ̊C.Cells were harvested at 4,000 rpm for 5 min, resuspendedin 400 μl Buffer Acontaining 50 mM Tris-HCl, 10 mM EDTA, 150 mM NaCl, 1%Triton X-100 and 1%SDSand weretransferred to a2 ml microcentrifuge tube. Equal volume ofphenol-chloroform solution was added to the abovesuspensionfollowed byvortexingfor 2-3 minand incubationat 42 ̊C for 30 minwithcontinuous agitation at 800 rpm on thermomixer (Eppendorf). Cell debris was removed bycentrifugation at 12,000 rpm for 5 minand aqueous fraction(~ 350 μl)was transferred to a new 2 ml microcentrifuge tube.0.3 μl RNaseCocktail™(Ambion® # AM2286) containing RNase A (500 U⁄ml) and RNase T1 (20,000 U⁄ml) was added and tubes were incubated at 37 ̊C for 30 min. DNA was precipitated with 2.5 volumesof chilled ethanol and 1/10thvolume of 3 M sodium acetate (pH 5.2).DNA pellet was washed with chilled 70%ethanol and semi-dried under air.Pellet was suspendedin 100μlTE (10 mM Tris-HCland 1 mM EDTA; pH 8.0)and stored at -20 ̊C.DNA concentration was determined by recordingabsorbance at 280 nmin Nanodrop (Nanodrop ND-1000, Thermo Scientific).

Protocol

Based on the subsequent use, DNA from C. glabratacells was extracted using three different methodologie

Yeast genomic DNA isolation

Molecular biology tech

preparedin appropriate solvents, sterilizedby autoclaving or filtrationand stored at appropriate temperature

For growth analysisof C. glabratastrains, a single colony from YPD or YNBagar mediumwas inoculated in appropriate liquid medium and incubated at 30 ̊C with shaking at 200 rpmfor 14-16 h. This overnight grown culture was used toinoculatetest medium to an initial OD600of 0.1to 0.3.Optical density/Absorbance of the cell suspensionwas measured using Ultraspec 2100 pro UV/visible spectrophotometer (Amersham Biosciences) at600nmat regular time-intervals up to a period of 96 h.Absorbance values were plotted with respect to time. Generation time of yeast strains wascalculated fromthe logarithmic (log) phase of cellgrowth. Growth profilesbetween 4 (t1)and 8 h(t2)time interval wereconsideredfor calculationof generation time usingfollowing formula. Generationtime(G)= (t2-t1) x {log (2)/ [log (Bf/Bi)]}G= Generation time in ht1=Initial timepoint taken for analysist2 = Final timepoint taken for analysisBf= Number of cells at time t2(calculated on the basis of OD600values, wherein1 OD600of C. glabratacorresponds to 2 X 107cells.)Bi= Number of cells at time t1(calculatedas mentioned above)Severalyeast strains used in this study were analysed for their susceptibility to variouschemical compounds,drugsand metal ions. For this purpose, stock solutions were

Growth assayand measurementof generation time

10 mg phosphatidylinositol-sodium salt(from Glycine max)was dissolved in 2 ml chloroform to prepare a 5 mg/ml stock solution. This solution was prepared in a small glass vial aschloroformis known to reactwith polypropylene. Small aliquots of stock solution were madeand stored at -20ºC till further use. To avoid spillage due to vapor pressure, vials containing phosphatidylinositol-sodium salt solutionwereopened very carefully.To prepare sonicated phosphatidylinositolfor one PI-3 kinase reaction, 2 μlof the stock phosphatidylinositolsolution (10 μg) wastransferredtoanew1.5 ml microcentrifuge tube. Using vacuum evaporator apparatus, chloroformwas evaporated from the solution and phosphatidylinositol-sodium saltwas resuspended in 5 μl sonication buffer.For sonication, a total of 20 pulses, each of 30 sec with30 sec resting time weregiven on ice

Preparation and sonication of phosphatidylinositol-sodium salt solution

homogenizedin 1 ml PBS and fungal burden was assessed by plating appropriate dilutions of tissue homogenate on YPD plates containing penicillin and streptomycinantibiotics (100units/mlpenicillin and 100μg/mlstreptomycin). All mice experiments were repeated twice with a set of 7-8 mice per strain in each experiment

Experiments involving mice were conducted at VIMTA Labs, Hyderabad.100 l YPD-grown C.glabratacellsuspension(4 X 107cells)was injected into female BALB/c mice (6-8 weeks old) through tail vein. Seven dayspost infection, mice weresacrificedand kidneys, liver,spleenand brainwere harvested. Organs were

Mouse infection assay

E. colistrains containing plasmids with unique oligonucleotide signature sequences were inoculated in LBmedium containing ampicillin and grown overnight at 37°Cand 200 rpm. Plasmids were extracted, quantitated anddenatured in alkaline denaturing solution. Approximately, 200 ng of each plasmid DNA was transferred to theHybond-Nmembraneusing96-well Dot Blot apparatus. Membranes were neutralized in 2X SSC and denatured plasmids were cross-linked to Hybond-N membranes usingUV cross linker

Membrane preparation

Genomic mapping of disrupted locusin Tn7insertion mutants was carried out as describedpreviously(Kaur et al., 2004).C. glabratamutants carrying Tn7insertionswere grown in YPD-liquid medium and genomic DNA was isolated fromovernight cultures. 10 μg genomic DNA was digested either with restriction enzyme MfeIor SpeI.Restriction enzyme-digestedDNA was precipitated with 1 ml ethanol and 1/10thvolume of sodiumacetate (3 M,pH 5.2). DNA pellet was washed twice with ice-cold 70% ethanol, air driedand was resuspended in sterilewater. DNA was recircularized with T4 DNA ligase.Resultant circular DNA carriedTn7cassette flanked on bothsidesby the disrupted locus oftheC. glabratagenome. CircularDNA wastransformed in E. coliBW23473 strainwhich contains protein Π (the product of the pirgene) required by R6Kγorifor replication.Twoverified transformants were grown overnight in LB-kanamycin medium and plasmids were extracted. Purified plasmids were sequenced withprimers reading outwards (OgRK 183 and OgRK 184) from both ends ofTn7cassette.Sequences obtained were compared,usingBLAST,against C. glabratagenome sequence database and regionsof Tn7insertions in C. glabratawere mapped

Mutant rescue

E. coli BW23473 electro-competent cell aliquots were taken out from -70ºC freezer, thawed on ice and were mixed with 1-2 lplasmid DNA. Mixture was pulsed with the Gene Pulser® electroporation apparatus (Bio-Rad),set at 1800 Volts, 25 μF and 200 Ω,in a chilled 0.1 cm electroporation cuvette. After electric pulse, 1 ml LB medium was immediately added to the cuvette and suspension was transferred to a 1.5 ml sterile microcentrifuge tube. Cells were incubatedat 37°C and 200 rpm for 1 h, centrifuged and were plated on LB-agar plates containing kanamycin (30 μg/ml). Transformants were colony purifiedon LB-kanamycin plates. Positive clones were verified by colony PCR and inoculated in LB-liquid medium containing kanamycin (30 μg/ml) for plasmid isolation

Transformation of E. coliBW23473 cells by electroporation

To prepareelectrocompetent cells, a single colony of E. coli BW23473 strain from a freshly-streaked LB agar plate was inoculated in 50 ml LB liquid medium. Culture was incubated at 37°C for 14 h with continuous shaking at 200 rpm. 25 mlovernight-grown E. coliBW23473 culture was transferred to 500 ml LB liquid medium and incubated at 37°C till the OD600 reached to 0.4. Post incubation, cultures were transferredto ice and centrifuged at 1,000g for 15 minat 4°C. Cells were washed twice with 500 ml ice-cold sterile water, three times with 250 ml ice-cold 10% glycerol solution and resuspended in 1 ml 10% glycerol solution. After absorbance measurement, cell suspension was normalized to final cell density of 3X1010cells/ml and dispensed in 50 μl aliquots to sterile ice-cold 1.5 ml microcentrifuge tubes. Aliquots were snap frozen in liquid nitrogen and stored at -70ºC

Preparation of E. coliBW23473electrocompetent cells

E. coliDH5α strain was transformed with plasmids carrying appropriate inserts to clone and generatedeletion strains of C. glabrataORFs(Sambrook, 2001). Ultracompetentcells stored at -70⁰C were thawed on icefor 5-10 min. 5 μlligated plasmid was added to100 μlultracompetent cells andcells were incubatedon ice. After 30 min, competent cells were subjected to heat shock at 42⁰C for 90 seconds. Cells were immediately transferredtoicefor 2-3min. Next, 800 μlSOC (or LB) medium was added and cells were allowed to recover for 45 minon a shaker incubator set at 37⁰C.After the recovery, cells were centrifuged at 2,500g for 4 min. Medium supernatant was discarded and cells were resuspended in 200 μlfresh sterile LBmedium. Cells were plated on LB agar medium containing appropriate antibiotics. Plates wereincubatedat37⁰C for 12-16 h

Bacterial transformation

10 min at 4 ̊C and gently resuspended in 20 ml ice-cold Inoue transformation buffer. To this cell suspension, 1.5 ml sterile DMSO was added and swirled gently. Cell suspension was kept on ice for 10 min and 50 μl volume was aliquoted to chilled sterile microcentrifuge tubes. Cells were immediately snap-frozen in liquid nitrogen and stored at -80 ̊C

A single colony of E. coli DH5α strain was inoculated in 10 ml LB medium and incubated at 37 ̊C for overnight. 4 ml overnight culture was inoculated in 2 lt SOB medium and incubated at 18 ̊C till the OD600 reached to 0.5. Cultures were centrifugedat 2,500 g for 10 min at 4 ̊C and harvested cells were washed gently with80 ml ice-cold Inoue transformation buffer. Cells were collected by centrifugation at 2,500 g for

Preparation ofE. coli DH5α ultracompetent cells

A microtipful of cellsfor each yeaststrainfrom appropriate mediumwassuspended in 10μlzymolyase cocktailandincubated at 37ºC for 90 min. 2 μlof zymolyase-treated cell suspension was used as template in 25 μlPCR reaction

Yeast colony PCR

Alipophilic styryl dye,FM4-64,is a vital stain which istakenupby cells viaendocytosis through plasma membrane(Vida and Emr, 1995). Therefore, it fluorescesonly in live cells. Importantly, neitherfixed cells canbe stained with FM 4-64norcells canbe fixed afterFM 4-64staining. For vacuole staining, single colony of the test strain grown onYPD plate was inoculated in 10 ml YPD medium for overnight. 100 μlovernight culture was inoculated in fresh YPD medium and incubated at 30ºC for 3 hto obtain log-phase cells. C. glabratacells from 1 ml log-phase culture were harvested at 4,000 rpm for 5 minin a table top centrifuge. Supernatant was aspirated out,cells were resuspended in 50 μl YPD medium and 1 μl FM 4-64 (16 μM final concentration) was added.C. glabratacells were incubated in a 30ºC water bath for 30 min. 1 mlYPD medium was added and cells were harvested at 4,000 rpm for 5 minin a table-top centrifuge. After discarding supernatant,C. glabratacells were washed with fresh YPD medium and resuspended in 1 ml YPD medium. C. glabratacells were incubated at 30ºC for 90 min, washed with 1 mlsterile water and were resuspended in 50 μl YNB medium. Labeled C. glabratacells were observed underfluorescence microscope in red filter(730nm)

Stainingof C. glabratavacuoleswith FM4-64

centrifugation at 5,000 rpm for 4 minat room temperature. Harvested cells werewashed with PBS and treated with different compoundse.g.H2O2. After treatment,cells were harvested and further processed according to the type of experiments performed

For several experiments, log-phase C. glabratacells were harvested and treated with different compounds. For this, single colony of aC. glabratastrain was inoculated in YPD-liquid medium and grown for 14-16 h at 30ºC withcontinuous shaking at 200 rpm. Overnight cultures were reinoculated in YPD medium to an initial OD600of 0.1 andgrown for another 4 h. These log-phase cells were harvested by

Harvesting of and treatment to logarithmic phase C. glabratacells

For opsonization,C. glabratacells were incubatedwith 1 μg/μl human IgG for 30 min at 37°C and washed thrice with PBS. Alternatively, yeast cells were incubated with 25% human serum at 37°C for 30 min followed by threePBS washes

Opsonizationof C. glabratacells

C. glabratastrains were grown overnight in YPD medium. Cellswereharvested from 1 mlcultureandwashed withPBS.Cells were next washed with50mM NaH2PO4andresuspendedin 100 μlFITC-dextran(50mg/ml). After incubation at 37°Cfor 45 min, cells were washed thrice with PBS for complete removal of FITC-dextran.Yeast cells were resuspended in 1 ml PBS and used to infect PMA-treated THP-1 cells in 4-chambered glass slide

Fluorescein isothiocyanate(FITC)staining of C. glabratacells

24 h post infection, THP-1 macrophages were washed thrice with PBS, lysed in water and recovered yeast cells were used to infect THP-1 cells at a MOIof 1:10. Three rounds of macrophage infection foreach mutant pool were carried out to enrich for the desired mutants in the final population. The lysate of 3rdround infection was inoculated in YPD medium for overnight (output). Cells were harvested, genomic DNA isolated from each input and output cell pellet andunique signature tags were PCR-amplified with P32-labeledα-dCTP using primers complementary to theinvariant region flanking each unique tag sequence. LabeledPCR products were denatured at 95°C for 10 min, chilled on ice and were hybridized tonylon membranescarrying immobilized plasmid DNA containing 96 unique tagsfor 14-16 h at 42°C.Membranes were washed twicewith 0.1X SSC bufferand exposed to phosphorimager screen for 2-4 h. Radioactive counts for each spot were quantified using Image Quant and Fuji Multi Gauge V3.0 software. Relative percentage intensity for individual spot was calculated with respect to allspots present oneach hybridizedmembrane

YPD-grown cultures (0.05 OD600) of each mutant pool (96 mutants, each carrying a unique signature tag) were either inoculated in YPD medium for overnight (input) or used to infect differentiated THP-1 cells (1X106). After 2 h incubation, non-cell-associated yeastcellswere removed by washing THP-1 cellsthricewith PBS. At

Screening of C. glabrataTn7insertion mutant library

Single colony of C. glabratastrains wasinoculated in 10ml YPD-liquid medium and grown at 30°C with constant shaking at 200 rpm for 14-16 h. Overnight culture was used to inoculate 10 ml YPD broth to an initial OD600of 0.1 and culture was grown for 4-5 h to obtain log-phase culture. Log-phase C. glabratacells were harvested in 15 ml sterile polypropylene tubesby centrifugation at 4,000 rpm for 5 min. Harvested cells were washed with10ml sterile water,resuspendedin 1 ml sterile water and transferred to a 1.5 ml microcentrifuge tube. Cells were harvested at 4,000 rpm for 5 minand resuspended in 100 μl of100mM lithium acetate solution.Yeast transformation cocktail was prepared in a 1.5 ml microcentrifuge tube by mixing 240 μlpolyethylene glycol(50%), 36μl lithium acetate(1 M) and25μlheat-denatured single stranded carrier DNA(2 mg/ml). 50 μlC. glabratacell suspension and 50 μltransforming DNAwas added to the transformation cocktail, mixed well andincubatedat 30 ̊C for45 min. 43 μlDMSO was added and cells were subjected to heat shock at 42 ̊Cfor 15 min. After the heat shock, cells were transferred to ice for 10-15 seconds, centrifuged at 4,000 rpm for 5 min and supernatantwas removed.Cells wereresuspended in 200 μlsterile water andspread platedonappropriate selectionmedium. Plates wereincubatedat30 ̊Cfor 2-3 days

Yeast transformation

Identified mutants were phenotypically characterized in 96-well plate format. Mutant cultures were grown in YPD medium for overnight, diluted 150-fold in PBS and 5 μl of cell suspension was spotted on different plates with a 96-pin replicator. Growth was recorded after 1-2 daysof incubation at 30°C

Phenotypic profiling

at 30°C andimages were captured after 2-8daysof incubationdepending upon the medium used

Yeast strains were grown in YPD medium for 14-16 hat 30°Cunder continuous shaking at 200 rpm. Cells were harvested from 1 mlculture, washed with PBS and were diluted to an OD600of 1. Five ten-fold serial dilutions were preparedfrom aninitial culture of 1OD600.4 μl cultureof each dilution was spotted onYNB-agar plates containing different carbon sources. For spotting on YPD plates containing different compounds, 3 μl cultureof each dilution was spotted. Plates were incubated

Serial dilution spotting assay

For growth analysis of a C. glabratastrain,single colony wasinoculated in appropriate broth medium and grown for 14-16 h. Overnight grown culture was used to inoculate the test medium toan initial OD600of 0.1-0.3. Cultures were transferred to a shaker incubator set at 30°C and 200 rpm. Absorbance ofcultures was measured using Ultraspec 2100 pro UV/visible spectrophotometer (Amersham Biosciences) at 600 nm at regular time-intervalstill 48h. Absorbancevalues were plotted with respect to time and generation time was determined from the logarithmic (log)phase of cell growth usingthefollowing formula.G = Generation time (h)T1= Initial time point taken for analysisT2= Final time point taken for analysisNf= Number of cells at time T2(1 OD600of C. glabrata corresponds to 2 X 107cells.)Ni= Number of cells at time T1(calculated from OD600value as mentioned above)

Growth analysis and determination of generation time

Bacterial strainEscherichia coli DH5αused for cloning purposewas revived on LB medium and grown at 37°C withcontinuous shaking at 200 rpm. LB medium was supplemented with appropriate antibiotics to growbacterial strains carrying plasmids. AnotherE. coli strain,BW23473,was used to rescue the Tn7transposon cassette from C. glabrataTn7insertion mutants. For plasmid DNA purification, bacterial strains were grown overnight in LB broth medium containingsuitable antibiotics

C. glabratastrains were routinely grown either in rich YPD medium or synthetically-defined YNB medium at 30°C withcontinuous shaking at 200 rpm unless otherwise stated. In general, C. glabratafrozen glycerol stocks wererevivedonYPD medium by streaking and allowed to grow for 1-2 days. C. glabratastrainsharboringthe plasmid with URA3as selectable marker were revived onCAA medium.To prepare liquid cell culture, single colony of eachC. glabratastrainwasinoculated either in YPD or YNB broth mediumand grown for 14-16 h. C. glabratastrains streaked on plates were storedat 4°C fora maximum period of2 weeks

Strains and culture conditions

Microbiological methods

To isolate primary peritoneal macrophages, 6-8 week old BALB/c mice were injected with 3% (w/v) thioglycollate broth (0.55% dextrose, 0.05% sodium thioglycollate, 0.5% sodium chloride, 0.05% agar)intraperitonealy (I.P. 50 μl/g body weight). After five days of injection, mice were euthanized by CO2inhalationand peritoneal macrophages were harvested byflushing the peritoneal cavity (lavage) with 10 mlDMEM medium(Zhang et al., 2008)

Isolation of primary (peritoneal) macrophages from BALB/c mice

For restriction digestion(either single or double), 0.5 to 1μg of DNA was used in a reaction containing2 to 5units of commercially available restriction enzyme(s)and 5μl of the recommended buffer (suppliedas 10X concentrationsby the vendor)in atotal reaction volume of 50μl. The reaction mixture was incubated for 2 h or overnight at 37°C. The digested DNA fragments were then visualised by ethidium bromide staining after electrophoresis on agarose gels. Commercially available DNA size markers were loaded along with the samples to ascertain or estimate the sizes of the digestedfragments

Restriction enzyme digestion

Automated DNA sequencing on plasmid templates or on PCR products was carried out with dye terminator cycle sequencing kits from Perkin-Elmer on an automated sequencer (model 377, Applied Biosystems), following the manufacturer’s instructions

DNA sequencing

Agarose gels were preparedby boiling appropriate amount of agarose in TAEbuffer. After dissolution, it was cooled and then poured in a casting tray containing a comb for desired number of wells. The gel was allowed to solidify and then shifted to horizontal electrophoresis tank containing TAE buffer. The DNA samples were mixed with appropriate volumes of 6X DNA loading dye, loaded on the gel andelectrophoresedat appropriate voltage and current conditions (generally 80 V,400 mA). The gel was stained in ethidium bromide solution(1 μg/ml)for 15-min at room temperature and visualisedby fluorescence under UV-light in a UV-transilluminator

Agarose Gel Electrophoresis

2μg of total RNA was reverse-transcribed using SuperScript III Reverse Transcriptase which is a commercially available version of M-MLVRT with reduced RNase H activity and increased thermal stability.According to manufacturer’s protocol1μg of RNA,1μl oligo(dT)(500ng),1μl 10mM dNTPand nuclease freewater was added to afinal volume of 13μlin a PCR tube.Thismixture was then incubated at 65°C for 5 minutesin a thermo cyclerand then quicklytransferredtoicefor 1minute. To this 4μl of 5X first strand buffer 1μl of 0.1MDTTand1μl ofRNaseOUT (40U/μl) were added. Then contents were then mixed and 1μl (200 units/μl) of SuperScript III RT was added. Themixture was then incubated at 50°C for 60 minutesin a thermo cycler.Lastlythe reaction was stopped byincubating the mixture at 70°C for 15 minutes. The cDNA thus prepared was then usedas a template for PCR

RT-PCR (Reverse Transcriptase PCR)

The quantity and purity of nucleic acids was determined by measuring the absorbance at 260 and 280 nm. The concentration of nucleic acids was calculated by considering the OD (λ260)= 1 corresponding to50μg/ml DNA and 40 μg/ml ofRNA. The purity of nucleic acids was checked by their A260/A280 ratioconsidering 1.8 for DNA and 2.0 for RNA. These measurements were done in NanoDrop 2000 UV-Vis Spectrophotometer

Quantification of nucleic acids

Total RNA was isolated by TRIzol method using the manufacturer’s protocol. Briefly, medium was removed from culture dish and recommended amount of TRIzol wasadded directly on to the dish and kept at room temperature for 5 minutes for lysis of cells. The cellular homogenate was then transferred to a 1.5ml microcentrifuge tube. For each mlof TRIzol, 200μl of chloroform was added and tubes were shaken vigorously for 10 seconds to completely dissociate the nucleoprotein complexes, followed by vortexing for about 30 seconds. The mixture was kept for 3-5 minutes at room temperature and then centrifuged at maximum speed of 12,000 rpm for 10 minutes. The upper aqueous phase was transferred into a fresh micro centrifuge tube and RNA was precipitated by adding 500μl of iso-propanol. The RNA pellet was obtainedby centrifugation at 12,000 rpm for 30 minutes at 4°C. The pellet was washed with 1ml of chilled 70% ethanol followed by centrifugation at 12,000 rpmfor 5minutes. The supernatant was removed and the pellet air-dried for about 5 minutes. The pellet was resuspendedin 30-50μl RNase free deionisedwater and dissolved at 55ºC followed by quantificationusingnanodrop spectrophotometerfor further use.The RNA integrity was checked by evaluating the 18S and 28S rRNA signals by running 1μl of total RNA on denaturing agarose gel stained with ethidium bromide

Total RNA isolation from cultured cells

Molecular techniques

Themixture is incubated in a water bath at 37⁰C for 15 min and afterwards transferred on ice and 4μl of DNA loading buffer is added. The samples were then run on a polyacrylamide gel electrophoresis which had been pre-run for 30 min. Electrophoresis was carried out at 4⁰C for 3h till the bromophenol blue migrated to 2cm above the bottom of gel. The gel was taken out and kept on Whatman filter paper sheet and covered by saran wrap followed by drying in a gel dryer at 80⁰C for 1h under suction. The dried gel was exposed to phosphoimager screen by keeping in phosphoimager cassette overnight

A binding reaction mixture was prepared by adding the following components to a microcentrifuge tube on ic

Binding reaction

Cells were seeded in replicates of five @ 3X103cells per wellinfive different 96well cell culture platesand grown in complete media. The method described earlier was slightly modified and followed (Gillies et al., 1986). After every 24h of seeding, one plate was stained with 0.2% crystal violet in 2% ethanolfor 15 minutestill 4thday i.e. 96h.One plate was stained just after the cells get attached to use as 0h time point. Excess dye was removed from the plates by washing with ample amount of water. Crystal violet dye incorporated in the cells was extracted using 0.1% SDS solution by shaking for 10 minutes on a shaker. Absorbance of the extracted dye was then determined at 570 nm in a spectrophotometer. The experiment was repeated at least three times and the average absorbance was plotted for each time point to generate a growth curve

Cell growth Assay

Transfection of plasmid DNAin cellswas performed using Lipofectamine 2000 reagent as per manufacturer’s protocolprovided with the reagent. Briefly, 0.5 to 1 million cells were seeded in a 60mm or 100mm tissue culture dish. After 12h of seeding,transfections were performed. 6-12 μg DNA was mixed in 500-1500 μl of Opti-MEM in one polypropylene tube and simultaneously, 15-30 μl of Lipofectamine 2000 was mixed in similar volumes of Opti-MEM in another tube and incubated at room temperature for 10minutes. Opti-MEM containingDNA and Lipofectamine 2000 were then mixed and incubated for 30 minutes at room temperature for the formation of DNA-lipid complex. Meanwhile, the cells were washed with sterile PBS and 4-10ml of Opti-MEM was addedin the plate. DNA-lipid complexes were then added to each dish for 6h. After that, the medium containing complexes was removed and complete medium (DMEM containing FBS) was added. Expression of transgene was evaluated 24-48hafter transfectioneitherby immunoblottingor immunofluorescence or by RT-PCR followed by PCR

Transient transfection in adherent cells

For growth analysis of S. cerevesiae strain, single colony was inoculated in appropriate broth medium and grown over night. This culture was used to inoculate the test medium to an initial OD600 of 0.1. Cultures were transferred to a shaker incubator set at 30°C and 200 rpm. Absorbance of cultures was measured using Ultraspec 2100 pro UV/visible spectrophotometer (Amersham Biosciences) at 600 nm at regular time-intervals till 72 h. Absorbance values were plotted with respect to time and the generation time was calculated from the logarithmic phase of the growth curve, by plotting A600vs.timeon a semi-logarithmic scale, using GraphPad Prism5 for curve fitting analysis

Growth analysis and determination of generation time

Plasmids containing the shRNA of interestwere either transfected transiently or were stably transfected. Transient transfection of shRNA was performed using eitherLipofectamine 2000 or PEI (as per the method explained before). Stable integration of shRNA was performed by transfecting shRNA along with retroviral packaging vector PCL-Ampho into BOSC23 packaging cells. The supernatantcontaining the packed viruses (viral medium)was collected at 48 and 72 hours of transfection. The viral mediumwas then added to thetarget cells in the presence of polybrene (8μg/mL). Two days later, cells were cultured in medium containing puromycin for the selection of stable clones.The clones stably expressing the desiredshRNA were identifiedandverified through western blotting and immunostaining using specificantibodies. A similar protocol was used to generate stable cell lines that expressed control shRNA

ShRNA

The plasmid-DNA/PEI mixture was incubated for 15 minutesat room temperature.The mixture was added to cells,andmixed properlyby rocking the culture plate back and forth. Cells were incubated at 37°C in a CO2 incubator.The transfected cells were harvested at 24-48 hours post-transfection

Cells were plated inthe cell culture dishes one day before transfection in RPMI1640 supplemented with FBS and penstrep (complete medium). All the reagents were brought to room temperature before starting transfection. Plasmid-DNA was diluted in serum-free medium and PEI was added(Table 9)Table 9: PEI plasmid-transfection methodology

Plasmid transfection using PEI

PCR products or plasmids were analyzed by agarose gel electrophoresis. The samples were mixed with 6X loading dye (0.25% bromophenol blue and 0.25% xylene cyanoland 30% glycerol in water) and loaded onto a pre-cast gel, the percentage of gel ranged from 0.7 to 3 %, depending on the size of the DNA sample. Ethidium bromide at 1 μg/ml was included in the gel. The gel was visualized by fluorescence under UV-light

Agarose gel electrophoresis

developer solution for appropriate time and immediately kept in fixer solution to see the protein band. For alkaline phosphatase method, blot was incubated with 5 ml of BCIP/NBT solution (Amresco) under dark condition. After incubation, blot was washed with water to see the blue-violet color protein band

volume of 50 mM acetate buffer (pH-5.4), and dialyzed overnight with 10 mM Tris buffer, pH 7.5. Pellet was used for dilution plating for calculating CFUs. For whole cell protein isolation, bacterial pellet was dissolved in 50 mM sodium acetate buffer (pH-5.4) and sonicated for 30 min (1 min on and off, Amplitude 32) by adding phenylmethylsulfonyl fluoride (PMSF) at a final concentration of 1 mM in ice-cold solution. Both extracellular proteins and whole cell lysate fractions were aliquoted in 1.5 ml microcentrifuge tube, and protein quantification was performed using a Pierce BCA protein assay kit (Thermo Scientific) as per manufacturer’s instructions using bovine serum albumin as standard and stored at -80°C for further use. Cell normalized extracellular and whole cell lysate proteins fractions from different strains were resolved on 12% SDS-PAGE gel at 90 V till the dye front reached the bottom. One gel was processed for silver staining (Sambrook et al., 1989), and other for western-blot analysis by using anti-GFP antibody. For western blot analysis, resolved proteins were transferred to Hybond-ECL membrane (Amersham biosciences) at 35 V for overnight in the cold room. Transfer of the proteins were visually confirmed by examining marker’s lane and membranes were incubated in small box for 2-3 h in 5% fat free milk prepared in 1X PBST for blocking. Blocking solutions were discarded, and primary antibody, appropriately diluted in 5% fat free milk prepared in 1X PBST, was added to the box containing membrane. After 2-3 h incubation in primary antibody, membranes were washed thrice with 1X PBST for 10 min. Membranes were incubated for 2 h in appropriate secondary antibody (anti-Rabbit antibody)diluted in 5% fat free milk prepared in 1X PBST. Blots were either developed by chemiluminescence based ECL-plus western detection system or alkaline phosphatase method. For HRP based chemiluminescence method, detection was performed using the ECL plus kit (Amersham biosciences) and incubated for 3 min. Blot was exposed to the film and developed i

For protein extraction, Xanthomonas oryzaepv. oryzaestrains with eGFP plasmid were grown for 24-30 h in PS medium to an OD of 0.8 as described above and centrifuged at 12,000 g for 10 min. The supernatant was taken as extracellular fraction and protein was extracted as described previously (Ray et al., 2000). Extracellular proteins were precipitated from this fraction by constantly adding 50% (wt/vol) ammonium sulphate at 4°C. After precipitation, the solution was kept on ice for 15-20 min and centrifuged at 12,000 g for 30 min at 4°C. The pellet was dissolved in s

Protein extraction and immunoblotting

respectively. The resulting constructs pRR14 and pRR15 were transferred in E.coliDH5α. Through triparental mating using pRK600 helper plasmid the construct were transferred in E.coliS17-1. After confirming pRR14 and pRR15 constructs by sequencing, the constructs were then introduced into BXOR1 strain through biparental mating using E. coliS17-1. X. oryzaepv. oryzicolaGUS and GFP reporter strains were selected on PS medium plates containing suitable antibiotics. Since pVO155 cannot replicate in X. oryzaepv. oryzae, ampicillin and kanamycin-resistant colonies were obtained upon chromosomal integration of the plasmid using the cloned DNA sequence as a region of homology. pProbeGTcan replicate independently in Xanthomonasand report for the gene expression

Glucuronidase (GUS) reporter gene fusion and GFP reporter fusion was created by using the suicide plasmid pVO155 having a promoterless gusAgene (Oke and Long, 1999), and pProbeGThaving a promoterless GFP (Miller et al., 2000). To construct the xsuA::gusAand xsuA::gfptranscriptional fusion, a 611-bp DNA fragment containing the putative promoter of the xssoperon (+213 to −398) was amplified by using the SCRsid_ pProbeGFP_F and SCRsid_ pProbeGFP_R primers (Table 2.2). This promoter fragment was subsequently digested with HindIII and BamHI,and directionally cloned upstream of the promoterless gusAand gfpgene in pVO155 and pProbeGTplasmids to create the xsuA::gusAand xsuA::pProbeGT(gfp) reporter constructs pRR1

Construction of xsuA::gusAand xsuA::gfp strains in X. oryzaepv. oryzicola background

(SCR65/ SCR66, SCR63/ SCR64 and SCR61/SCR62, respectively) designed from the neighbourhood region of the deleted gene.Replacement of ΔrpfFdeletion mutant with the point mutant allele (E141A and E161A: Glutamate to Alanine) (rpfF*) was carried out by transforming XocΔrpfFmutant with pbsks suicide vector harbouring full length rpfF* allele. The DNA fragment carrying the rpfF* allele was constructed by overlap PCR as described previously (Ionescu et al., 2013)using two 21 and 28 bp complementary primers for E141A-F/R and E161A-F/R, respectively; harbouring GAA to GCA substitution (Table 2.2). The mutated rpfF* allele was amplified by using the end primers only (SC14 and SC17) and cloned into pbsks vector with HindIII and XhoI restriction sites. The resulting suicide vector (pRR16 and pRR17) was transformed into ΔrpfFmutant and single recombinants were selected on PSA medium with kanamycin and ampicillin. Colonies were screened for integration of rpfF* (E141A or E161A) allele through homologous recombination with the flanking region of deleted rpfF allele

electroporation. Single Kmr recombinants were selected on PSA plate containing kanamycin. Insertion of the pK18mob vector in xssAgene was confirmed with PCR and sequencing. To further confirm the mutation in the siderophore biosynthetic gene, we did siderophore production assay on Peptone-sucrose agar (PSA)-chrome azurol sulfonate (CAS) (Schwyn and Neilands, 1987). PSA-CAS plate assay indicated that the xssA mutnat of Xocwas deficient in production of secreted siderophore.Deletion of the chromosomal rpfG, rpfC andclpgene of the X. oryzaepv. oryzicolawas accomplished by allelic exchange, following homologous recombination, utilizing the suicide vector pK18mobsacB harboring 5’ region and 3’ regions of the gene of interest (Katzen et al., 1999). 5’ and 3’ regions of rpfG and rpfC andclp gene were first amplified from the BXOR1by PCR using primers indicated in Table no. 2.2 and products were ligated together. After restriction digestion of ligated PCR products and the pK18mobsacB vector with appropriate restriction enzymes, they were ligated to get the plasmids pRR9, pRR10 and pRR11, respectively. These plasmids were then transformed into E. coliDH5α cells. The transformed E. colicells were selected on the LB agar plates containing nalidixic acid and kanamycin. The positive colonies carrying vector with correct inserts were further selected by colony PCR. These donor cells carrying pRR9, pRR10 and pRR11 containing 5’ and 3’ regions of the gene of interest were then transformed into electrocompetent BXOR1 wild-typecells. First crossover (single crossover) was achieved by culturing the cell mixture on Nutrient agar(NA) containing rifampicin and kanamycin,after transformation. The second crossover was allowed by passaging the cells with single crossover in nutrient brothmedium and then selecting on PSAplates containing rifampicin and 5% sucrose. BXOR1with deletion of the rpfG,rpfCand clp genes by double crossover was identified by PCR using pri

Two fragments, each approximately 300 bp in length corresponding to 5’and 3’ end of the rpfFgene were amplified using genomic DNA of Xocwild-type strain BXOR1, and cloned in pBSKS vector to obtain pRR7 (Table S1 and S5). pRR8 was obtained after ligation of Kmrcassette (EZ::Tn5TM<Kan-2>; Madison, WI) in the HindIII site of pRR7. The resulting plasmid (pRR8) was introduced into XocBXOR1 strain by electroporation. Doublerecombinants (Kmrand Aps) were screened on PSA plates containing appropriate antibiotics. Deletion of rpfF(76 amino acids) in the ∆rpfF mutant strain was confirmed by PCR and sequencing. For complementation analysis, full lengthrpfF gene was amplifiedfrom genomic DNA of Xoc Wild-typeBXOR1 strain with HindIII and EcoRI restriction sites and cloned into stable broad host range vector pHM1 (Hopkins et al., 1992)downstream to lacZpromoter to obtain pSC9. The pSC9 plasmid harboring the wild-typerpfFallele was introduced into ∆rpfF mutant strain by electroporation.To obtain the insertional nonpolar mutant in the xssA(xanthomonas siderophore synthesis A), a 321 bp internal fragment of the xssAgene containing the XbaI and HindIII sites was cloned inpK18mob suicide vector, in which the lacZpromoter drives the expression of downstream gene (Schäfer et al., 1994; Windgassen et al., 2000)to obtain pRR12. The resulting plasmid (pRR12) was introduced into Xoc BXOR1 strain by

Construction of mutants in X. oryzaepv. oryzicolaand rescue of the mutation

confirmed through PCR (by using primers SC11 and SC10) and squencing. Double mutant was complemented for DSF production by cloning whole rpfFgene of Xoo, cloned in HindIII and EcoRI sites of pHM1 (a broad host range vector for Xanthomonas) to get pSC6 plasmid. The resultant pSC6 plasmid was introduced into double mutant by electroporation

To obtain the insertional nonpolar mutant in the motA (encodes flagellar motor stator protein)andfliC (flagellin)genes, a 321 bp internal fragment of the motAgene and a 450 bp internal fragment of fliC containing the EcoRI and XbaI site were amplified using respective primer listed in Table 2.2. These fragments were cloned in pk18mob suicide vector, in which the lacZpromoter drives the expression of downstream gene (Schäfer et al., 1994; Windgassen et al., 2000), to obtain pRR1 and pRR2,respectively (Table 2.2). The resulting plasmid (pRR1& pRR2) was introduced into XooBXO43 strain by electroporation. Single Kmrrecombinants were selected on PSA plate containing kanamycin. Insertion of the pK18mob vector in motA andfliCgene was confirmed with PCR and sequencing. To further confirm the mutation in the flagellar genes, we did swimming motility assay on 0.1% peptone-sucrose agar (PSA). Swimming plate assay indicated that both motA and fliCmutant of Xoowas deficient in motility. Further, to obtain motAand fliC insertional knock out mutants in rpfFbackground, we cloned spectinomycin cassette obtained from pUC1318Ω plasmid, into the HindIII site of pRR1 and pRR2 plasmid to obtain pRR3 and pRR4. The resulting plasmid (pRR3& pRR4) were transformed in rpfF. Single specrrecombinants were selected on PSA plate containing kanamycin and spectinomycin. Insertion of the vector was further confirmed by PCR and sequencing. T2SSrpfFdouble mutant was constructed by transforming the plasmid with rpfF::Tn7Kanamycin cassette in the T2SS (xpsF) mutant background, and Kmrrecombinants were selected on PSA plates containing kan

Construction of mutants in X. oryzaepv. oryzae

insert of 1:3 for sticky end ligations. Ligation mix was incubated either at 22°C for 30 min or 16°C for 14-16 h. After incubation, T4DNA ligase was inactivated at 65°C for 20 min

After restriction enzyme digestion, digested products were resolved on agarose gels, and desired DNA fragments were extracted from the gel. Otherwise digested DNA fragments were precipitated by Phenol-choloroform-isoamyl alcohol method. Concentration of gel extracted or precipitated fragments were determined using spectrophotometer and ligation reactions were set up using a molar ratio

Ligation

For DNA precipitation after digestion, 500 μl nuclease free water was added to the digested DNA fragment. Equal volume of phenol:chloroform:isoamyl alcohol (25:24:1) was added to the mixture and centrifuged at 13,000 g for 10 minat RT. Upper aqueous phase containing DNA fragment was transferred to fresh microcentrifuge tube and DNA was precipitated by adding 0.7 volume of iso-propanol and 1/10thvolume of sodium acetate. Precipitated DNA was washed with 70% ethanol, pellet was air dried for 20-30 min at RT and dissolved in nuclease-free water

DNA precipitation

QIAGEN QIAquick Gel extraction kit containing required buffers, spin columns and collection tubes was used to extract and purify DNA from agarose gels. Digested DNA samples and PCR products were resolved on 1% agarose gel and gel piece containing desired fragment was cut on an UV-transilluminator. DNA fragment was purified following manufacturer’s instructions

Gel extraction of DNA

strain or the ∆rpfFmutantharboring the Wild-typeallele in plasmid (pSC9).Genes that were significantly up regulated by 0.6 or more or down regulated by -0.6 or less fold (log2–fold change) were identified.The microarray data have been deposited in the NCBI Gene Expression Omnibus (GEO) under the GEO series accession number GSE53255

8x15k (AMADID: 25096) custom Agilent platform comprised of coding sequences for the three strains of Xanthomonas-X. oryzaepv. oryzae(KACC10331), X. oryzaepv. oryzicola(BLS256) and X. axonopodispv. citri 306 gathered from National Center for Biotechnology Information (NCBI). A total of 8113 probes were designed wherein 2120 probes corresponding to genes of interest replicated three times on Agilent platform. Feature extraction software GeneSpring GX version 10.5.1 of Agilent and GeneSpring GX percentile shift normalization was used for data analysis. Genes that were significantly up or down regulated by more than 1.5 fold and less than 0.5 fold were identified. Hierarchical clustering was performed for the differentially regulated genes and classified based on functional category. Data are the average of two hybridizations from biological replicates of each sample andraw data sets for this study are available at the Gene Expression Omnibus database (Accession number –GSE217809). Likewise, Microarray analysis for Xanthomonas oryzaepv. oryzicolawas performed by isolating RNA from the strains grown under low-ironcondition. The labeled cRNA samples were hybridized on to a Genotypic Technology Private Limited designed 8x15k (AMADID: 41087) Agilent platform. Data extraction from Images was done using Feature Extraction software v 10.7 of Agilent. Data normalization was done in GeneSpring GX using 75thpercentile shift and normalization to specific samples. Differentially regulated genes were clustered hierarchically to identify significant gene expression patterns.Genes were classified based on functional category. Hierarchical clustering of DSF regulated genes in X. oryzaepv. oryzicola grown under low-iron conditions is based on similar expression profiles in ∆rpfFmutant vs either the Wild-typeBXOR1 strain or ∆rpfF(pSC9). Clustering analysis was performed using GeneSpring GX Software using Average Linkage rule with pearson uncentered distance metric. log2–fold change differences between the ∆rpfFmutant with either the Wild-typeBXOR1

Xanthomonas oryzae pv. oryzae strains grown in PS medium to an OD600of 1, were collected, washed once with 150 mM sodium chloride (NaCl) solution to remove excess EPS. RNA isolation was performed using Trizol method described above. After isopropanol precipitation, RNA was frozen at -80°C. Quality of RNA was examined by determining the RNA integrity number (RIN) before microarray analysis. Microarray experiments were performed at Genotypic Technology Pvt. Ltd., Bangalore.Briefly, a

Microarray analysis

BXOR1, ΔrpfFand ΔrpfF(pSC9) strains were grown to OD600of 1 in rich media (PS), PS + 50 μM 2,2’-dipyridyl (DP) and PS + DP + 30 μM FeSO4. RNA was isolated by Trizol (Invitrogen) method as described above. Optimal primer and cDNA concentrations were standardized, and qRT-PCR was performed using ABI 7500 Fast Real-Time PCR system (Applied Biosystems). In brief, 1 μl cDNA, 0.25 picomoles of gene specific primers and 10 μl 2X SYBR GREEN qPCR Mastermix (Qiagen)were mixed in the wells of 96-well PCR plate (Axygen). Final reaction volume was adjusted to 20 μl with nuclease-free water. Transcript levels were quantified with an end-point value known as Ct(cycle thresold) value. Expression of 16S rRNA was used as an internal control. The Ct values defines the number of PCR cycles required for the fluorescent signal of SYBR green dye to cross beyond the background level. Fold-change in transcript expression was determined using following formula.Fold change in expression = 2-ΔΔCtΔΔCt= ΔCt treated-ΔCt untreatedΔCttreated = Ctvalue for the gene of interest under treated condition -Ct value for the internal control gene (16S rRNA) under treated conditionΔ Ctuntreated = Ct value for thegene of interest under untreated condition -Ct value for the internal control (16S rRNA) gene under untreated condition

Primers for real-time PCR analysis were designed using Primer3 plus software and are listed in Table 2.2.For RNA isolation, X. oryzaepv.oryzaewild-type, rpfFmutant, rpfF/CG8 complemented strains were grown in PS medium at 28°C for 28 h at 200 rpm. Similarly, for RNA isolation from X. oryzaepv. oryzicola, the Wild-type

Quantitative real-time PCR

Complementary-DNA synthesis was performed using reverse transcriptase enzyme (Invitrogen) and random hexamers (Qiagen). For this, 1 μg good quality RNA was treated with 1 μl (1 unit) DNase I (Invitrogen) for 20 min to remove DNA contamination. Next, Superscript III Reverse Transcriptase kit (Invitrogen) was used to synthesize cDNA according to the manufacturer’s instructions. cDNA synthesized was further confirmed by using it as a template for amplification in PCR. cDNA was stored at -20°C till further use

Synthesis of complementary DNA (cDNA)

work were autoclaved twice and dried at 80°C for overnight before use. RNA was isolated from Xanthomonasculture using Trizol method. Xanthomonascells were harvested at 12,000 g for 5 min at 4°C, resuspended in approximately 1 ml Trizol (Invitrogen),mixed properly and incubated at room temperature (RT) for 5 min. 200 μl chloroform was added to the tube, shaken for 15 seconds and incubated at RT for 2-15 seconds. Next, tubes were centrifuged at 13,000 g for 15 min at 4°C. Aqueous phase was transferred to new 1.5 ml microcentrifuge tube and RNA was precipitated by adding 500 μl isopropanol and incubated for 5-10 min at RT. Precipitated RNA was collected by centrifugation at 10,000 gfor 10 min at 4°C. RNA pellet was washed with 70% ethanol and resuspended in 20 μl nuclease-free water. RNA concentration was determined by measuring absorbance at 260 nm. Quality of RNA was examined by gel electrophoresis on 0.8% agarose gel with TAE buffer prepared in DEPC treated water

For RNA experiments, all solutions were prepared in RNase free diethylpyrocarbonate (DEPC) treated water. Microcentrifuge and tips u

RNA extraction

Xanthomonasstrains were grown overnight in 3 ml PS medium. Cells were harvested at 12,000 g for 5 min, resuspended in RNase added P1 buffer and were transferred to 2 ml microcentrifuge tube. Cells were lysed by adding 40 μl lysozyme followed by adding 80 μl 10% SDS and incubated at 50°C for 10 min. Further, proteins were removed by treating the cell suspension with 16 μl proteinase K and incubated at 37°C for overnight. Next day, 200 μl CTAB/NaCl was added and cell suspension was heated at 65°C for 10 min. Next, 1 ml chloroform-isoamyl alcohol was added to the cell suspension and tubes were vortexed for 2-3 min. After centrifugation at maximum speed for 10 min at room temperature, aqueous phase was carefully transferred to a fresh microcentrifuge tube. To further remove cell debris, previous step was repeated with 1 ml of phenol-chloroform-isoamyl alcohol and aqueous phase containing DNA was taken out carefully. Genomic DNA from the aqueous phase was precipitated by adding 700 μl isopropanol and 170 μl sodium acetate (3M, pH-7). Next, DNA pellet was washed with 70% ethanol and dried at room temperature for 20 min. Genomic DNA pellet was dissolved in 50 μl nuclease free water and stored at -20°C. Quality of extracted genomic DNA was checked on 0.7% agarose gel by electrophoresis

Xanthomonasstrains were grown overnight in 3 ml PS medium. Cells were harvested at 12,000 g for 5 min, resuspended in RNase added P1 buffer and were transferred to 2 ml microcentrifuge tube. Cells were lysed by adding 40 μl lysozyme followed by adding 80 μl 10% SDS and incubated at 50°C for 10 min. Further, proteins were removed by treating the cell suspension with 16 μl proteinase K and incubated at 37°C for overnight. Next day, 200 μl CTAB/NaCl was added and cell suspension was heated at 65°C for 10 min. Next, 1 ml chloroform-isoamyl alcohol was added to the cell suspension and tubes were vortexed for 2-3 min. After centrifugation at maximum speed for 10 min at room temperature, aqueous phase was carefully transferred to a fresh microcentrifuge tube. To further remove cell debris, previous step was repeated with 1 ml of phenol-chloroform-isoamyl alcohol and aqueous phase containing DNA was taken out carefully. Genomic DNA from the aqueous phase was precipitated by adding 700 μl isopropanol and 170 μl sodium acetate (3M, pH-7). Next, DNA pellet was washed with 70% ethanol and dried at room temperature for 20 min. Genomic DNA pellet was dissolved in 50 μl nuclease free water and stored at -20°C. Quality of extracted genomic DNA was checked on 0.7% agarose gel by electrophoresis

Genomic DNA isolation

200 rpm in LBbroth supplemented with appropriate antibiotics (plasmid antibiotic marker). Cells were harvested by centrifugation at 12,000 g for 5 min. Plasmids were extracted using Qiagen plasmid miniprep ormidiprep kit following the manufacturer’s instructions. Concentration of the extracted plasmid DNAs was measured using spectrophotometer at 280 nm and stored at -20°C

E.colistrains carrying plasmids were inoculated and grown overnight at 37°C and

Plasmid DNA purification

All standard molecular biology and genetics were performed as described previously (Sambrook et al. 1989)

Molecular biology methods

For growth analysis of Xanthomonasstrains, a loopful of bacterial colony was inoculated in appropriate broth medium and grown for 14-16 h. 0.2% of overnight grown culture was used to inoculate the test medium (for iron limitation, PS with 50 or 100 μM of 2,2’-dipyridyl, and for iron supplementation, different concentrations of either FeCl3or FeSO4was added). Cultures were transferred to a shaker incubator set at 28°C and 200 rpm. Absorbance of cultures was measured using Ultraspec 2100 pro UV/visible spectrophotometer (Amersham Biosciences)at 600 nm at regular time-intervals till 48 h. Absorbance values were plotted with respect to time and generation time was determined from the logarithmic (log) phase of bacterial growth using the following formula.G = Generation time (h)T1= Initial time point taken for analysisT2= Final time point taken for analysisNf = Absorbance at time T2(Final OD)Ni= Absorbance at time T1(Initial OD)

Growth analysis and determination of generation time

For mouse infection assay, 10 ml YPD medium was inoculated with different C. glabratastrains and allowed to grow at 30°C for 12-16 h. After growth,cultures were washed twice in sterile 1X PBS and the cell pellet was resuspended in appropriate volume of 1X PBSto obtain a cell density corresponding to20OD600. 100 μlcell suspension(4x107yeast cells)was injected into female BALB/c mice (6-8 weeks old) through tailvein. Seven days post

infection, mice were sacrificed and kidneys, liver, brain and spleen were harvested. Organs were homogenised in 1 ml PBS and appropriate dilutions of tissue homogenate were plated onYPD-agar mediumsupplemented with penicillin and streptomycin antibiotics (100 units/ml penicillin and 100 μg/ml streptomycin). Plates were incubated at 30°C for 24-48 h and CFUs were counted. Fungal burden in different organs wasdetermined by multiplying the CFUsobtainedwithanappropriate dilution factor

For mouse infection assay, 10 ml YPD medium was inoculated with different C. glabratastrains and allowed to grow at 30°C for 12-16 h. After growth,cultures were washed twice in sterile 1X PBS and the cell pellet was resuspended in appropriate volume of 1X PBSto obtain a cell density corresponding to20OD600. 100 μlcell suspension(4x107yeast cells)was injected into female BALB/c mice (6-8 weeks old) through tailvein. Seven days post

Mouse infection assay

microcentrifuge tube. For precipitation of RNA, 1/10thvolume of 3 M sodium acetate (pH 5.3) and 2.5 volume of 100% ice-coldethanol was added. In order to facilitate precipitation, tubes werekept at -20°C for 20 min. Tubes were centrifuged at 13,000 rpm for 10 min in a refrigerated centrifuge. The RNA pellet was washed with 70% ethanol,resuspendedin 100-200 μl of nuclease-free water and stored at -20°C untiluse.Care was taken to keep allreagents and tubes on ice to maintain the cold temperature throughout theRNA extractionprocess

All reagents required for RNA extraction were preparedin DEPC-treated water. RNasecontamination from non-autoclavable items wasremoved by wiping them with RNaseZap® (Ambion). Total RNA from yeast cells was extractedusing acid phenolextractionmethod. Briefly, yeast cells were grown underappropriate conditions and at suitabletime points,cells were harvested by centrifugation at 4,000 rpm for 5 min. The cell pellet was washed twice with ice-cold DEPC-treated water, resuspended in 350 μl of AE buffer and transferred toa1.5 ml microcentrifuge tube. To this,40 μl of 10% SDS and 400 μl of acid phenol (pH 4.3) was added. The cell suspension was mixed well by vortexing thrice, short pulsesof10 seconds each,and incubated at 65°C for 15 min with continuous agitation at 800 rpm. Post incubation, cells were kepton ice for 5 min and centrifuged at 13,000 rpm in a refrigerated centrifuge set at 4°C for 10 min. After centrifugation, aqueous layer was transferred to a new1.5 ml microcentrifuge tube and 400 μl of chloroform was added. Tubes were mixed well by gentlyinverting them 4-5 times and centrifuged at 13,000 rpm for 10 min. The aqueous layer was separated and transferred to a new1.5 ml

Total RNA isolation

This method was used to isolate highly pure genomic DNA. Briefly, 10 ml overnight grownC. glabratacultures were spun downandwashed with 10 ml sterile water. Washed cells wereresuspended in500 μl sterile water and transferred toa1.5 ml microcentrifuge tube. Tubes were spundownat 4,000 rpm for 5 min, supernatant was discarded andcell pellet was resuspended in 500 μl of buffer containing 100 mM EDTA and 5% β-mercaptoethanol and incubatedat 42°C for 10 min. Post incubation, cells were spun down at 4,000 rpm for 5 min and resuspended in freshly prepared Buffer B. To this, one tip-full of lyticase (Sigma, L4025) was added and incubated at 37°C for 1 h.After incubation, spheroplasts were collected by spinning downtubes at 6,000 rpm for 5 min, supernatant was discarded and the pellet was resuspended in 500 μl of Buffer C. DNA was extracted twice with 500 μl of PCI (25:24:1) solution and the aqueous layer was transferred toa new1.5 ml microcentrifuge tube. To this, 2.5 volume of absolute ethanol and 1/10thvolume of 3 M sodium acetate (pH 5.3) wereadded. Tubes were spundownat 13,000 rpm for 10 min, DNA pellet was resuspended in 200 μl of 1X TE buffer containing0.3 μl of RNase cocktail (Ambion) and incubated at 37°C for30 min. DNA was precipitated again by adding absolute ethanol and sodium acetate as mentioned above. DNA pellet was washed once with 70% ethanol, centrifuged at 13,000 rpm for 10 min, air-dried at room temperature and was resuspended in 100-200 μl of 1X TE buffer by gently tapping the tube. DNAwas stored at -20°C until use

Spheroplast lysis method

Bacterial transformation

microcentrifuge tube. For precipitation of RNA, 1/10thvolume of 3 M sodium acetate (pH 5.3) and 2.5 volume of 100% ice-coldethanol was added. In order to facilitate precipitation, tubes werekept at -20°C for 20 min. Tubes were centrifuged at 13,000 rpm for 10 min in a refrigerated centrifuge. The RNA pellet was washed with 70% ethanol,resuspendedin 100-200 μl of nuclease-free water and stored at -20°C untiluse.Care was taken to keep allreagents and tubes on ice to maintain the cold temperature throughout theRNA extractionprocess

All reagents required for RNA extraction were preparedin DEPC-treated water. RNasecontamination from non-autoclavable items wasremoved by wiping them with RNaseZap® (Ambion). Total RNA from yeast cells was extractedusing acid phenolextractionmethod. Briefly, yeast cells were grown underappropriate conditions and at suitabletime points,cells were harvested by centrifugation at 4,000 rpm for 5 min. The cell pellet was washed twice with ice-cold DEPC-treated water, resuspended in 350 μl of AE buffer and transferred toa1.5 ml microcentrifuge tube. To this,40 μl of 10% SDS and 400 μl of acid phenol (pH 4.3) was added. The cell suspension was mixed well by vortexing thrice, short pulsesof10 seconds each,and incubated at 65°C for 15 min with continuous agitation at 800 rpm. Post incubation, cells were kepton ice for 5 min and centrifuged at 13,000 rpm in a refrigerated centrifuge set at 4°C for 10 min. After centrifugation, aqueous layer was transferred to a new1.5 ml microcentrifuge tube and 400 μl of chloroform was added. Tubes were mixed well by gentlyinverting them 4-5 times and centrifuged at 13,000 rpm for 10 min. The aqueous layer was separated and transferred to a new1.5 ml

Total RNA isolation

This method was used to isolate highly pure genomic DNA. Briefly, 10 ml overnight grownC. glabratacultures were spun downandwashed with 10 ml sterile water. Washed cells wereresuspended in500 μl sterile water and transferred toa1.5 ml microcentrifuge tube. Tubes were spundownat 4,000 rpm for 5 min, supernatant was discarded andcell pellet was resuspended in 500 μl of buffer containing 100 mM EDTA and 5% β-mercaptoethanol and incubatedat 42°C for 10 min. Post incubation, cells were spun down at 4,000 rpm for 5 min and resuspended in freshly prepared Buffer B. To this, one tip-full of lyticase (Sigma, L4025) was added and incubated at 37°C for 1 h.After incubation, spheroplasts were collected by spinning downtubes at 6,000 rpm for 5 min, supernatant was discarded and the pellet was resuspended in 500 μl of Buffer C. DNA was extracted twice with 500 μl of PCI (25:24:1) solution and the aqueous layer was transferred toa new1.5 ml microcentrifuge tube. To this, 2.5 volume of absolute ethanol and 1/10thvolume of 3 M sodium acetate (pH 5.3) wereadded. Tubes were spundownat 13,000 rpm for 10 min, DNA pellet was resuspended in 200 μl of 1X TE buffer containing0.3 μl of RNase cocktail (Ambion) and incubated at 37°C for30 min. DNA was precipitated again by adding absolute ethanol and sodium acetate as mentioned above. DNA pellet was washed once with 70% ethanol, centrifuged at 13,000 rpm for 10 min, air-dried at room temperature and was resuspended in 100-200 μl of 1X TE buffer by gently tapping the tube. DNAwas stored at -20°C until use

Spheroplast lysis method

E. coliDH5α ultra-competent cells were used for all bacterial transformations. Briefly, frozen DH5α ultra-competent cells were taken out from -80°C freezerandthawed on ice for 15 min. DNA to be transformed was added to the bacterial cell suspension and incubated on ice for 30 min. For transforming ligation mixtures and plasmids,5-10 μl and 100-500 ng of DNA was used, respectively. Followed by 30 min incubation on ice, heat shock was given for 60-90 sec at 42°C in a water bath and cells were immediately kept back onice for 2 min. To this,1 ml of sterile LB medium was added and tubes were incubated inashaker incubator set at 37°C, 200 rpm for 45 min.Next, cells were spun down and resuspended in 500 μl of LB medium. About 100-200 μl of resuspended cells were plated on LB-agar medium containing appropriate antibiotics and incubated for 12-16 h at 37°C. Transformants were purified on LB-agar plates containing appropriate antibiotics andpositive transformantscarrying desired DNAwere verified by PCR, restriction digestion and sequencing analyses