Fig. 7. Ectopic PAL-1 activates the muscle-like program independent of HLH-1. The left panels (A) shows the MHC A pattern on the left side of a comma stage wild-type embryo (top) and a diagram of the body wall muscle nuclei (bottom; adapted from Sulston et al., 1983). In the center (B), treatment of wild-type embryos (top) with mex-3, pop-1 double RNAi results in widespread myogenesis as indicated by MHC A staining. The same treatment in a presumed hlh-1(cc450) mutant null genetic background (bottom: see text for details) results in similar amounts of ectopic muscle, although MHC A expression appears weaker. The right panels (C) show similar results in embryos treated with heat shock-induced PAL-1 and pop-1 RNAi in either a wild-type (top) or an hlh-1 RNAi (bottom) embryo. Images in B and C are representative of focal planes throughout the embryo.