Figure 8

Increased activity of lin-39 and mab-5 can rescue some defects in ceh-13 mutant animals. A-B, A gain-of-function mutation in mab-5, e1751, suppresses lethality in ceh-13(-) mutants. Note that most of the double mutant animals look superficially normal. B, Extra copies of lin-39 suppress larval lethality in ceh-13(sw1) mutants. "+++" represents an integrated translational fusion LIN-39::GFP reporter that is able to rescue the Vul phenotype of lin-39 hypomorph mutants (~5%, N = 122). ND, not determined. C, mab-5(e1751gf) mutation restores the lifespan of ceh-13(-) mutants to a nearly normal level. Note that the vast majority of ceh-13(-) single mutants die at early stages of development (Figure 8A, B), and the survivals (escapers) live only few days as adults (i.e., they are extremely short-lived). For double mutants, normal looking L4 stage larvae were selected and then scored for survival (yellow curve). Samples were assayed in triplicates. For ceh-13(sw1) single mutants, ~70 mutant escapers were examined in each assay. For the other strains, 150-150 animals were scored in each assay. p < 0.001, when ceh-13(lf)mab-5(gf) double mutants were calculated to ceh-13(lf) single mutants by pair-wise comparisons, and p > 0.5 when double mutants were compared to the wild type. The log-rank test was used for comparison. N2 indicates wild-type. D, mab-5::gfp expression in wild-type (left panel) vs. ceh-13(sw1) mutant (right panel) background at the L1 larval stage. Nomarski pictures on the top, corresponding fluorescent images at the bottom. White arrows indicate cells that are gfp-positive. E, Phylogenetic tree of homeodomain sequences of the C. elegans Hox genes. The tree was generated by the Bayesian phylogenetic method. Numbers at the nodes correspond to the probability - i.e., clade credibility - of each node (from 0 to 1). F, Model for the early evolution of the nematode Hox cluster. A ceh-13-like primordial Hox gene underwent a tandem gene duplication event in an early phase of animal evolution, leading to the ancestors of the primitive anterior and posterior Hox genes. A subsequent tandem duplication of the anterior ancestor resulted in the ancestor of the middle-group Hox genes. A: anterior, P: posterior, M: Middle.