A selfish genetic element confers non-Mendelian inheritance in rice

Abstract

Selfish genetic elements are pervasive in eukaryote genomes, but their role remains controversial. We show that <i>qHMS7</i>, a major quantitative genetic locus for hybrid male sterility between wild rice (<i>Oryza meridionalis</i>) and Asian cultivated rice (<i>O. sativa</i>), contains two tightly linked genes [<i>Open Reading Frame 2</i> (<i>ORF2</i>) and <i>ORF3</i>]. <i>ORF2</i> encodes a toxic genetic element that aborts pollen in a sporophytic manner, whereas <i>ORF3</i> encodes an antidote that protects pollen in a gametophytic manner. Pollens lacking <i>ORF3</i> are selectively eliminated, leading to segregation distortion in the progeny. Analysis of the genetic sequence suggests that <i>ORF3</i> arose first, followed by gradual functionalization of <i>ORF2</i> Furthermore, this toxin-antidote system may have promoted the differentiation and/or maintained the genome stability of wild and cultivated rice.