eLife assessment
This fundamental study provides insight into the fascinating process of self- and non-self-recognition in the protist Tetrahymena thermophila, a species with seven distinct mating types. Using an elegant combination of phenotypic assays, protein studies, and imaging, the authors present convincing evidence that a large multifunctional protein complex at the cell surface mediates both self- and non-self mating-type recognition. This study extends our understanding of how more than two mating types/sexes may be specified in a species, and it will be relevant for anyone interested in sexual systems and cell-cell communication.