The masculinizing gene
her-1 in Caenorhabditis 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 expressed sequence tag, 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. Injection of dsRNA transcribed from
Cb-her-1 into C. briggsae hermaphrodites (RNA interference) 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 only very weak, if any, masculinization. We conclude that in spite of considerable divergence the Cb gene is likely to be a functional ortholog of
Ce-her-1, while the function of the distantly related Bm gene remains uncertain.