FAMK-1 expression in the spermatheca maintains spermathecal integrity and organismal fertility. (A) Immunoblot of the products of the two transgenes schematized above in the absence of endogenous FAMK-1. Actin serves as a loading control. (B) Images of a nuclear GFP reporter expressed under control of the spermathecal promoter psth-1. The reporter shows strong expression in the spermatheca and weaker signal in two cells in the vulval region; no additional expression was observed. Scale bar, 10 µm. (C) Spermatheca morphology analysis for the indicated conditions conducted using DIC imaging. Representative images show a normal, abnormally distended (double arrow), and oocyte fragment (arrowhead)–containing spermatheca. Scale bar, 10 µm. Graph shows frequency of defective spermatheca for the indicated conditions. (D) Embryonic lethality and fertility analysis for the indicated conditions. ****, P < 0.0001; **, P < 0.01 (t tests).