title: Context-dependent function of a conserved translational regulatory module.
abstract: The modification of transcriptional regulation is a well-documented evolutionary mechanism in both plants and animals, but post-transcriptional controls have received less attention. The derived hermaphrodite of C. elegans has regulated spermatogenesis in an otherwise female body. The PUF family RNA-binding proteins FBF-1 and FBF-2 limit XX spermatogenesis by repressing the male-promoting proteins FEM-3 and GLD-1. Here, we examine the function of PUF homologs from other Caenorhabditis species, with emphasis on C. briggsae, which evolved selfing convergently. C. briggsae lacks a bona fide fbf-1/2 ortholog, but two members of the related PUF-2 subfamily, Cbr-puf-2 and Cbr-puf-1.2, do have a redundant germline sex determination role. Surprisingly, this is to promote, rather than limit, hermaphrodite spermatogenesis. We provide genetic, molecular and biochemical evidence that Cbr-puf-2 and Cbr-puf-1.2 repress Cbr-gld-1 by a conserved mechanism. However, Cbr-gld-1 acts to limit, rather than promote, XX spermatogenesis. As with gld-1, no sex determination function for fbf or puf-2 orthologs is observed in gonochoristic Caenorhabditis. These results indicate that PUF family genes were co-opted for sex determination in each hermaphrodite via their long-standing association with gld-1, and that their precise sex-determining roles depend on the species-specific context in which they act. Finally, we document non-redundant roles for Cbr-puf-2 in embryonic and early larval development, the latter role being essential. Thus, recently duplicated PUF paralogs have already acquired distinct functions.
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Qinwen
authors.initials: Q
authors.lastname: Liu
authors.forename: Craig
authors.initials: C
authors.lastname: Stumpf
authors.forename: Cristel
authors.initials: C
authors.lastname: Thomas
authors.forename: Marvin
authors.initials: M
authors.lastname: Wickens
authors.forename: Eric S
authors.initials: ES
authors.lastname: Haag
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans; D019143:Evolution, Molecular; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008858:Microscopy, Phase-Contrast / Q000379:methods; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D014176:Protein Biosynthesis; D034622:RNA Interference; D019076:Transgenes; D020798:Two-Hybrid System Techniques