Postembryonic expression of Caenorhabditis elegans mab-21 and its requirement in sensory ray differentiation

The male tail sensory rays in Caenorhabditis elegans are complex copulatory structures, the normal patterning of which requires a number of regulatory genes. Among them, mab-21 specifies the identity of sensory ray 6. By usin g green fluorescent protein reporters, we identify multiple cis-acting elem ents that control the developmental expression of mab-21. Traced with a fun ctional mab-21::gfp gene driven by authentic regulatory sequences, mab-21 e xpression could be detected in hypodermal, neuronal, muscle, and ray cells. We showed here that the expression of mab-21 in the hypoderm-is and neuron al cells was dispensable for its function mi ray 6. In contrast, its expres sion in the ray 6 structural cell and neurons as conferred by its 3' enhanc er was crucial for determining the correct ray 6 identity. (C) 2001 Wiley-L iss, Inc.