Combinations of Spok genes create multiple meiotic drivers in Podospora

Abstract

Meiotic drive is the preferential transmission of a particular allele during sexual reproduction. The phenomenon is observed as spore killing in multiple fungi. In natural populations of <i>Podospora anserina</i>, seven spore killer types (<i>Psk</i>s) have been identified through classical genetic analyses. Here we show that the <i>Spok</i> gene family underlies the <i>Psk</i>s. The combination of <i>Spok</i> genes at different chromosomal locations defines the spore killer types and creates a killing hierarchy within a population. We identify two novel <i>Spok</i> homologs located within a large (74-167 kbp) region (the <i>Spok</i> block) that resides in different chromosomal locations in different strains. We confirm that the SPOK protein performs both killing and resistance functions and show that these activities are dependent on distinct domains, a predicted nuclease and kinase domain. Genomic and phylogenetic analyses across ascomycetes suggest that the <i>Spok</i> genes disperse through cross-species transfer, and evolve by duplication and diversification within lineages.