The conserved nuclear receptor Ftz-F1 is required for embryogenesis, moulting and reproduction in Caenorhabditis elegans

Background: Nuclear receptors are essential players in the development of a ll metazoans. The nematode Caenorhabditis elegans possesses more than 200 p utative nuclear receptor genes, several times more than the number known in any other organism. Very few of these transcription factors are conserved with components of the steroid response pathways in vertebrates and arthrop ods. Ftz-F1, one of the evolutionarily oldest nuclear receptor types, is re quired for steroidogenesis and sexual differentiation in mice and for segme ntation and metamorphosis in Drosophila. Results: We employed two complementary approaches, direct mutagenesis and R NA interference, to explore the role of nhr-25, a C. elegans ortholog of Ft z-F1. Deletion mutants show that nhr-25 is essential for embryogenesis. RNA interference reveals additional requirements throughout the postembryonic life, namely in moulting and differentiation of the gonad and vulva. All th ese defects are consistent with the nhr-25 expression pattern, determined b y in situ hybridization and GFP reporter activity. Conclusions: Our data link the C. elegans Ftz-F1 ortholog with a number of developmental processes. Significantly, its role in the periodical replacem ent of cuticle (moulting) appears to be evolutionarily shared with insects and thus supports the monophyletic origin of moulting.