The adenylate cyclase/protein kinase cascade regulates entry into meiosis in Saccharomyces cerevisiae through the gene IME1

Entry into meiosis in Saccharomyces cerevisiae cells is regulated by starvation through the adenylate cyclase/cAMP-dependent protein kinase (AC/PK) pathway. The gene IME1 is also involved in starvation control of meiosis. Multicopy IME1 plasmids overcome the meiotic deficiency of bcy1 and of RAS^val19 diploids. Double mutants ime1 cdc25 and ime1 ras2 are sporulation deficient. These results suggest that IME1 comes after the AC/PK cascade. Furthermore, the level of IME1 transcripts is affected by mutations in the AC/PK genes CDC25, CYR1 and BCY1 Moreover, the addition of cAMP to a cyr1-2 diploid suppresses IME1 transcription. The presence in a bcy1 diploid of IME1 multicopy plasmids does not cure the failure of bcy1 cells to arrest as unbudded cells following starvation and to enter the G₀ state (thermotolerance, synthesis of unique G₀ proteins). This indicates that the pathway downstream of the AC/PK cascade branches to control meiosis through IME1, and to control entry into G₀ and cell cycle initiation, independently of IME1.