eLife Assessment
This study makes an important contribution by characterizing the role of the exocyst in secretory granule exocytosis in the Drosophila larval salivary gland. The results are solid and lead to the novel interpretation that the exocyst participates not only in exocytosis, but also in earlier steps of secretory granule biogenesis and maturation. However, the authors are urged to provide additional proof that the exocyst subunit knockdowns were effective and to acknowledge the possibility that inactivation of an essential exocytosis component could indirectly affect other parts of the secretory pathway.