The masculinizing gene
her-1 in C. elegans (
Ce-her-1 ) encodes a novel protein, HER-1A, which is required for male development. To identify conserved elements in
her-1 we have cloned and characterized two homologous nematode genes: one by synteny from the closely related free-living species C. briggsae (
Cb-her-1 ), and the other, starting with a fortuitously identified EST, from the distantly related parasite Brugia malayi (
Bm-her-1 ). The overall sequence identities of the predicted gene products with Ce -HER-1A are only 57% for Cb -HER-1, which is considerably lower than has been found for most homologous briggsae genes, and 35% for Bm -HER-1. However, conserved residues are found throughout both proteins, and like Ce -HER-1A, both have putative N-terminal signal sequences.
Ce-her-1 produces a larger masculinizing transcript (
her-1a) and a smaller transcript of unknown function (
her-1b); both are present essentially only in males. By contrast,
Cb-her-1 appears to produce only one transcript, corresponding to
her-1a; it is enriched in males but present also in hermaphrodites. Although this suggests different regulatory mechanisms, comparisons of upstream and intron-2 sequences identified elements common to both Caenorhabditis species. Injection of dsRNA transcribed from
Cb-her-1 into C. briggsae hermaphrodites caused XO animals to develop into partially fertile hermaphrodites. Introducing a
Cb-her-1 construct as a transgene under control of the C. elegans
unc-54 myosin heavy chain promoter caused strong masculinization of both C. briggsae and C. elegans hermaphrodites. Introduction of a similar
Bm-her-1 construct into C. elegans caused weak masculinization. Therefore, in spite of considerable divergence the Cb gene is likely to be a functional ortholog of
Ce-her-1 , and the distantly related Bm gene may be as well.