Fig. 1. Ectopic expression of Hox genes and other defects in sor-1 loss-of-function mutants. (A) Expression of egl-5 in a wild-type L2 larva. The expression of egl-5 is restricted to the tail (not shown) and is absent in the head (bracket). (B) Ectopic expression of egl-5 in a sor-1 mutant. egl-5 is ectopically expressed in many head neurons (marked with bar). (C) Expression of mab-5 in a wild-type larva. The expression of mab-5 is confined to the posterior region (arrow). (D) Ectopic expression of mab-5 in a sor-1 mutant. mab-5 is expressed in the head neurons and hypodermal cells. The expression of mab-5::gfp is absent from the tail region (arrow). (E) Normal expression of pkd-2::gfp in all nine pairs of B-type ray neurons (arrow) and in four head neurons (arrowhead) in a wild-type male. PKD-2::GFP marks both the cell body and the axon of neurons. (F) Ectopic expression of pkd-2::gfp in a sor-1(RNAi) male, indicating that ectopic rays are generated in the anterior body region. Five ectopic rays are located between the arrows. (G) sor-1 mutant hermaphrodites have a protruding vulva phenotype (arrow). (H) Partial hermaphrodite-to-male sexual transformation. An ectopic male ray (arrow), as visualized with pkd-2::gfp, is generated in a sor-1 hermaphrodite. This animal also contains a pkd-2::gfp-positive neuron in the head (arrowhead), which is normally expressed in four male-specific head neurons.