GENETIC AND MOLECULAR ANALYSIS OF SPE-27, A GENE REQUIRED FOR SPERMIOGENESIS IN CAENORHABDITIS-ELEGANS HERMAPHRODITES

Hermaphrodites with mutations in the spe-27 gene are self-sterile, lay ing only unfertilized eggs; mutant males are fertile. Hermaphrodites m ake spermatids that fail to activate to crawling spermatozoa so passin g oocytes sweep them out of the spermatheca. These spermatids do activ ate and produce self-progeny if young mutant hermaphrodites are mated by fertile (or sterile) males. Spermatids isolated from either mutant males or hermaphrodites initiate activation in vitro when treated with proteases, but then arrest with spiky membrane projections that resem ble those of a normal intermediate in pseudopod formation. These pheno types are identical to spe-8 and spe-12 mutants. They can be explained if males and hermaphrodites have distinct pathways for spermatid acti vation, and these three genes are necessary only for the hermaphrodite pathway. Consistent with this model, when spe-27 mutant male spermati ds without seminal fluid are artificially inseminated into hermaphrodi tes, they fail to activate. The Spe-27 gene has been isolated, sequenc ed and its regulatory regions identified. The sequence predicts a 131 amino acid polypeptide that has no striking structural motifs and no r esemblance to known proteins. Two of the mutations in spe-27 alter mRN A splicing; a third mutation is a temperature-sensitive missense mutat ion.