Ovulation in Caenorizabditis elegans requires inositol 1,4,5-triphosphate (IP3) signaling activated by the epidermal growth factor (EGF)-receptor homolog LET-23. We generated a deletion mutant of a type I 5-phosphatase,
ipp-5, and found a novel ovulation phenotype whereby the spermatheca hyperextends to engulf two oocytes per ovulation cycle. The temporal and spatial expression of IPP-5 is consistent with its proposed inhibition of IP3 signaling in the adult spermatheca.
ipp-5 acts downstream of
let-23, and interacts with
let-23-mediated IP3 signaling pathway genes. We infer that IPP-5 negatively regulates IP3 signaling to ensure proper spermathecal contraction.