Based on published sequences for chicken Bcl-2,three siRNAs(small interfering RNA)were designed,and expression vectors were constructed and transfected into goose granulosa cells cultured in vitro.Bcl-2 protein,apoptosis and proliferation of granulosa cells,48 h after the transf ection,were analyzed by flow cytometry,and progesterone(P)secreted into the culture medium was measured by radioimmunoassay.In addition,apoptosis and Bcl-2 protein level were assessed in untreated granulosa cells from the four largest preovulatory follicles(F1F4),the smallest preovulatory follicles(SPF),small yellow follicles(SYF)and atretic follicles.The highest level of Bcl-2 protein was observed in granulosa cells from SPF,and levels in cells from healthy follicles were significantly higher than those of atretic follicles(P【0.05).Bcl-2 protein levels in cells subjected to RNAi were significantly lower than those of controls(P【0.05),while apoptosis indices(AI),proliferation indices(PI)and P secretion in the RNAi treatments were higher than those of controls(P【0.05).