The Caenorhabditis elegans sex-determining gene
tra-2 promotes female development and expresses 4.7-, 1.9- and 1.8-kb mRNAs. The 4.7-kb mRNA encodes the major feminizing activity of the locus, a predicted membrane receptor that mediates cell-to-cell communication, named TRA-2A. The
tra-2 gene was characterized from a close relative, C. briggsae. The
Cb-tra-2 gene expresses only a 4.7-kb mRNA and alternatively spliced variants, which encode TRA-2A homologues. The Cb-TRA-2A and Ce-TRA-2A sequences are highly diverged, sharing only 43% identity, although their hydropathy profiles remain remarkably similar. Three potential regulatory sites of
Ce-tra-2 activity were previously identified by analyzing
tra-2(eg),
tra-2(gf), and
tra-2(mx) mutations. Two of these sites, the EG site and MX region, are conserved in
Cb-tra-2. By contrast, the two direct repeat elements in the
Ce-tra-2 3' untranslated region, which are disrupted in
tra-2(gf) mutants, are absent. Injection of
Cb-tra-2 antisense RNA into C.briggsae mimics the
Ce-tra-2 loss-of-function phenotype. Thus, antisense RNA permits studies of gene activity in nematodes that lack extensive genetics.