In C. elegans, consistent with a previous report, OA synthetic enzymes are highly expressed in the spermatheca and the proximal gonadal sheath.
tbh-1 expression in the gonadal sheath begins from the late larval stage 4 (L4), when diplotene-stage oocytes appear, while
tbh-1 expression in RIC interneurons in the head begins as early as at the L1 stage. This
tbh-1 expression in gonadal sheath cells accounts for the observation that adult C. elegans produce at least five times more OA than larvae, which express OA only in RIC29. The level of TBH-1 is the strongest in the proximal three pairs of gonadal sheath cells, which cover the meiotic oocytes in- waiting, suggesting a potential OA function in oocyte quiescence. Strong expression in the spermatheca, which are involved in fertilizing and moving the fertilized eggs, suggests a role of OA in ovulation, as has been reported in D. melanogaster.