A chimeric gene paternally instructs female sex determination in the haplodiploid wasp <i>Nasonia</i>.

Abstract

Various primary signals direct insect sex determination. In hymenopteran insects, the presence of a paternal genome is needed to initiate female development. When absent, uniparental haploid males develop. We molecularly and functionally identified the instructor sex-determination gene, <i>wasp overruler of masculinization</i> (<i>wom</i>), of the haplodiploid wasp <i>Nasonia vitripennis</i> This gene contains a P53-like domain coding region and arose by gene duplication and genomic rearrangements. Maternal silencing of <i>wom</i> results in male development of haploid embryos. Upon fertilization, early zygotic transcription from the paternal <i>wom</i> allele is initiated, followed by a timely zygotic expression of <i>transformer</i> (<i>tra</i>), leading to female development. <i>Wom</i> is an instructor gene with a parent-of-origin effect in sex determination.