CDC-25.1 controls the rate of germline mitotic cell cycle by counteracting WEE-1.3 and by positively regulating CDK-1 in Caenorhabditis elegans.

In Caenorhabditis elegans, cdc-25.1 loss-of-function mutants display a lack of germline proliferation. We found that the proliferation defect of cdc-25.1 mutants was suppressed by wee-1.3 Further, among the seven cdk and seven cyclin homologs examined, cdk-1 and cyb-3 treatment caused the most severe germline proliferation defects in an rrf-1 mutant background, which were similar to those of the cdc-25.1 mutants. In addition, while duanyu1615 of cyd-1 and cye-1 caused significant germline proliferation defects, duanyu1615 of cdk-2 and cdk-4 did not. Compared with the number of germ nuclei in worms, the number in and worms further decreased to the level of and worms, respectively, indicating that cdk-1 and cyb-3 are epistatic and function downstream of cdc-25.1 and wee-1.3 in the control of the cell cycle. BrdU labeling of adult worms showed that, while 100% of the wild-type germ nuclei in the mitotic region incorporated BrdU when labeled for more than 12 h at 20°C, a small fraction of the cdc-25.1 mutant germ nuclei failed to incorporate BrdU even when labeled for 68 h. These results indicate that CDC-25.1 is required for maintaining proper rate of germline mitotic cell cycle. We propose that CDC-25.1 regulates the rate of germline mitotic cell cycle by counteracting WEE-1.3 and by positively controlling CDK-1, which forms a complex primarily with CYB-3, but also possibly with CYD-1 and CYE-1.

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