Fig. 1. Loss of eel-1 enhances efl-1(se1) to a Mex phenotype. The top row contains Nomarski images of terminally developed C. elegans embryos from eel-1(RNAi), efl-1(se1) and efl-1(se1);eel-1(RNAi) mothers incubated at 20°C. Note that eel-1(RNAi) and efl-1(se1) embryos form enclosed pretzel-shaped embryos and appear as wild type. By contrast, efl-1(se1);eel-1(RNAi) embryos do not enclose and fail to elongate. The center row shows comparable embryos stained for pharyngeal muscle to demonstrate that efl-1;eel-1(RNAi) embryos produce an excess of this tissue in comparison with embryos from either single mutant mother. The bottom row contains images of the MED-1:GFP expression pattern at the 15-cell stage. This expression pattern is wild-type in eel-1(RNAi) (n=25 of 25) and efl-1(se1) (n=22 of 23) single-mutant embryos; MED-1:GFP is expressed only in a subset of descendants of the posterior cell of the 2-cell embryo. In efl-1(se1);eel-1(RNAi) embryos (n=25 of 30), MED-1:GFP is ectopically expressed in descendants of the anterior blastomere of the 2-cell embryo. Embryos are oriented with anterior to the left. Scale bar: 10 µm.