Fig. 4. pal-1 regulates ced-3 expression and cell death in the tail-spike cell. (A) A 0.7 kb C. briggsae ced-3 promoter::GFP reporter (nsIs25) is expressed in a surviving tail-spike cell (arrow; inset: GFP only) of a ced-3(n717) L2 larva. (B) Same reporter as in A in a pal-1(ns114); ced-3(n717) L2 larva imaged using the same exposure time (arrow: binucleate tail-spike cell; inset: GFP only). Notice the decreased GFP fluorescence in the tail-spike cell of the pal-1 mutant. (C) Image of a distinctive tail-spike cell corpse (green and inset) persisting in a ced-5(n1812); nsIs25 L1 larva. Anterior is to the left. (D) pal-1 is required for tail-spike cell death and acts in parallel to egl-1. For each genotype, between 20-52 L1 animals were scored for tail-spike cell corpses, as identified by position, shape and expression of the nsIs25 C. briggsae ced-3 promoter::GFP transgene. Error, s.e.m. Alleles used: ced-5(n1812), pal-1(ns114, ns115), egl-1(n1084n3082). Scale bars: 10 µm.