SELF-STERILITY OF EGGS INDUCED BY EXOGENOUS AND ENDOGENOUS PROTEASE IN THE SOLITARY ASCIDIAN, HALOCYNTHIA-RORETZI

The unfertilized eggs (UFE) of the solitary ascidian, Halocynthia rore tzi, which are released naturally, are strictly self-sterile. However, ovarian eggs isolated after spawning, which ave expected to develop i nto UFE on the following day, ave self-fertile. Some exogenous proteas es-trypsin, chymotrypsin, papain and elastase-induced self-sterility i n the self-fertile ovarian eggs within an hour in vitro. The establish ment of self-sterility by the exogenous protease did not require the s ynthesis of new protein, or the participation of follicle cells. Some of the ovarian eggs were able to differentiate into self-sterile eggs spontaneously in vitro. The protein synthesis inhibitors puromycin and cycloheximide had no effect on the spontaneous establishment of self- sterility. However, several protease inhibitors such as leupeptin, soy bean trypsin inhibitor (SBTI) and antipain, did inhibit the spontaneou s establishment of self-sterility, The possible participation of tryps inlike protease in the establishment of self-sterility in the ovary is discussed, Mol. Reprod. Dev. 52:99-106, 1999. (C) 1999 Wiley-Liss, In c.