There are four
cdc-25 family members in C. elegans. CDC-25s dephosphorylate inhibitory phosphorylation of CDKs, which are phosphorylated by WEE-1 family members. Defect of each
cdc-25 family member showed sterility. In this study, we analyzed functions of
cdc-25.2 in somatic cells. We found that a loss-of-function mutant,
cdc-25.2(
ok597), produced less number of intestinal nuclei due to defects in E-lineage division.
cdc-25.2(
ok597) had only 16 intestinal nuclei at the adult stage while wild type had 30-34, indicating that CDC-25.2 activity is required for intestinal division after 16E stage. To determine whether 16E cells are generated by maternal CDC-25.2 product loaded from heterozygous
cdc-25.2/+ mother, we also examined
cdc-25.2(
ok597) progeny from the homozygous mother. Lack of maternally loaded CDC-25.2 did not enhance
cdc-25.2(
ok597) mutant phenotype, suggesting that other
cdc-25 family members are involved in early, but not after 16E stage. To test this possibility, we observed
cdc-25.1(
rr31gf);
cdc-25.2(
ok597) double mutant. Both L1 larvae and adults of
cdc-25.1(
rr31gf);
cdc-25.2(
ok597) double mutant showed lower number of intestinal nuclei (25.6 plusminus 1.9) than
cdc-25.1(
rr31gf) single mutant L1 larvae (39.6plusminus1.1) and adults (59.0plusminus3.4), suggesting that CDC-25.1 functions prior to CDC-25.2.
cdc-25.1(
rr31gf) undergoes extra intestinal division during embryogenesis due to prolonged presence of CDC-25.1. On the other hand,
cdc-25.2(
ok597);
cdc-25.3(
ok358) double mutant produced the same number (16) of intestinal nuclei as
cdc-25.2(
ok597) single mutant, indicating that
cdc-25.3 is not essential for intestine development. These results suggest that CDC-25.2 solely regulates intestinal division after 16E stage. Non-divided intestinal nuclei in
cdc-25.2(
ok597) mutants contained double amount of DNA compared to normal nuclei, suggesting that intestinal nuclei in
cdc-25.2(
ok597) mutant are arrested at G2-M transition after DNA synthesis. RNAi of
cdk-1 and
cyb-1 also decreased the number of intestinal nuclei, while
wee-1.3 RNAi in
cdc-25.2(
ok597) mutant partially suppressed the intestinal phenotype, suggesting that CDC-25.2 positively regulates CDK-1 by counteracting WEE-1.3 through dephosphorylation of CDK-1/CYB-1 complex.