Model for IME1 activation by Rie1–Sgn1. Top: In vegetatively growing cells, IME1 transcription is repressed and Rie1–Sgn1 abundance is low. IME1 mRNAs that arise by leaky transcription will have a low probability of encountering Rie1–Sgn1 activators. Bottom: At meiosis onset, IME1 transcription and Rie1–Sgn1 abundance are increased by pro-sporulation cues. IME1 transcripts now have a higher probability of encountering Rie1–Sgn1 complexes due to the increased ratio of IME1 mRNA to total mRNA as well as the increased availability of Rie1–Sgn1.