Fig. 1. Models and MPK-1 MAPK activation. (A) In the proximal gonad, somatic ovarian sheath cells surround the oocytes, which are in diakenesis of meiotic prophase. Sperm are stored in the spermatheca and export the cytoskeletal protein MSP to induce oocyte meiotic maturation, MPK-1 MAPK activation and sheath contraction. The maturing oocyte signals the dilation of the spermathecal valve, and the oocyte is fertilized as it enters the spermatheca. (B) Simplified depiction of the block versus switch models for the control of oocyte maturation (MAT). See text for details. (C-I) MAPK-YT staining of wild-type and mutant gonads. (C) In wild-type gonads, sperm trigger MPK-1 MAPK activation in the oocyte(s) most proximal to the spermatheca. (D) In itr-1(sa73) hermaphrodites, more oocytes contain activated MAPK than in the wild type. (E) MAPK activation is not observed in unmated fog-3(q443) females. (F) By contrast, MAPK activation is frequently observed in unmated unc-43(n498gf); fog-3(q443) females. (G) More oocytes contain activated MAPK in vab-1(dx31) hermaphrodites, a phenotype identical to itr-1(sa73) hermaphrodites (D). (H) In itr-1(sy290gf) unc-24(e138) hermaphrodites, fewer oocytes contain activated MAPK than control hermaphrodites. (I) The MAPK activation frequency in vab-1(dx31); itr-1(sy290gf) unc-24(e138) hermaphrodites is similar to itr-1(sy290gf) unc-24(e138) hermaphrodites, suggesting that itr-1 acts downstream of vab-1. All gonads are oriented as shown in A. The MAPK activation pattern in G has previously been reported elsewhere (Miller et al., 2003). Scale bar: 10 µm.