A fission yeast SNAP-25 homologue, SpSec9, is essential for cytokinesis and sporulation.

The soluble NSF attachment protein 25 (SNAP-25) is a component of the SNARE complex that is essential for regulated exocytosis in diverse cell types. Here, we identified a fission yeast SNAP-25 homologue, SpSec9. The sec9+ gene was essential for vegetative growth. sec9 mRNA was detected in vegetative cells and further increased during sporulation. This increase during sporulation was dependent on Mei4, a meiosis-specific transcription factor. A sporulation-deficient sec9 mutant was isolated by random PCR mutagenesis (sec9-10). The sec9-10 mutant also exhibited temperature sensitivity for growth and cell division was found to arrest before completion of cell separation at restrictive temperatures. In sec9-10 cells, the forespore membrane was normally initiated near spindle pole bodies during meiosis II. However, subsequent extension of the membrane was severely impaired. These results indicate that SpSec9 plays an important role both in cytokinesis and in sporulation.