Figure 4.

daf-2 and pdk-1 independently regulate the core apoptosis pathway. L4 stage (a, c, d) or young adult (b) worms were irradiated and germ cell apoptosis was quantified after 24 h at 20°C (b and c), or 25°C (a and d). Owing to the somatic effects of daf-2 and pdk-1 loss on the visibility of the germline in daf-2ced-9 and ced-9; pdk-1 double mutants, we found it necessary to perform these two epistasis experiments at slightly different developmental time points (48 h post-L4 in the case of daf-2ced-9 and 24 h post-L4 for ced-9; pdk-1). As worms age from L4 to young adult, the germline continues to expand in size and this is reflected by a small increase in basal levels of apoptosis. Therefore, the absolute levels of apoptosis seen in ced-9(0) mutants in the daf-2ced-9 experiment is greater than that seen in the ced-9; pdk-1 experiment. This should not alter our interpretation of epistasis, however, as loss of pdk-1 exerts an ∼1.3-fold greater suppressive effect on ced-9(0) than does loss of daf-2. daf-2(lf)=daf-2(e1370), ced-9(0)=ced-9(n2812), ced-4(0)=ced-4(n1162). Error bars as in Figure 1