Schizosaccharomyces pombe Sst4p, a conserved Vps27/Hrs homolog, functions downstream of phosphatidylinositol 3-kinase Pik3p to mediate proper spore formation.

Sporulation of the fission yeast Schizosaccharomyces pombe is a developmental process that generates gametes and that includes the formation of spore envelope precursors called the forespore membranes. Assembly and development of forespore membranes require vesicular trafficking from other intracellular membrane compartments. We have shown that phosphatidylinositol 3-kinase (PtdIns 3-kinase) is required for efficient and proper development of forespore membranes.