Fig. 1. CDK-1 is required for MEI-1 degradation and this requirement cannot be suppressed by loss of EGG-3.

(A) Embryos in uteri of hermaphrodites of indicated genotypes were scored for GFP:MEI-1 and for position with respect to the spermatheca [from youngest (position 1) to oldest (position 6)]. In mat-1(RNAi), GFP:MEI-1 is maintained in all embryos, but degradation is restored if egg-3 is also absent. In cdk-1(RNAi), GFP:MEI-1 is maintained past the third position embryo, and this “delayed degradation” pattern is not changed significantly in the absence of egg-3. Unlike mat-1(RNAi), which efficiently maintains MBK-2 at the cortex, cdk-1(RNAi) leads to a more pleiotropic arrest with embryos eventually releasing MBK-2 into the cytoplasm, which may explain why GFP:MEI-1 is eventually degraded in cdk-1(RNAi).

(B) A genetic model describing the epistasis results obtained in A. cdk-1 is required to initiate meiotic M phase (Burrows et al., 2006), and therefore is considered formally here as an “activator” of the APC subunit mat-1.