Genome elimination mediated by gene expression from a selfish chromosome

Abstract

Numerous plants and animals harbor selfish B chromosomes that "drive" or transmit themselves at super-Mendelian frequencies, despite long-term fitness costs to the organism. Currently, it is unknown how B chromosome drive is mediated, and whether B-gene expression plays a role. We used modern sequencing technologies to analyze the fine-scale sequence composition and expression of paternal sex ratio (PSR), a B chromosome in the jewel wasp <i>Nasonia vitripennis</i>. PSR causes female-to-male conversion by destroying the sperm's hereditary material in young embryos to drive. Using RNA interference, we demonstrate that testis-specific expression of a PSR-linked gene, named <i>haploidizer</i>, facilitates this genome elimination-and-sex conversion effect. <i>haploidizer</i> encodes a putative protein with a DNA binding domain, suggesting a functional link with the sperm-derived chromatin.