OlCHR, encoding a chromatin remodeling factor, is a killer causing hybrid sterility between rice species Oryza sativa and O. longistaminata

Abstract

The genetic mechanisms of reproductive isolation have been widely investigated within Asian cultivated rice (<i>Oryza sativa</i>); however, relevant genes between diverged species have been in sighted rather less. Herein, a gene showing selfish behavior was discovered in hybrids between the distantly related rice species <i>Oryza longistaminata</i> and <i>O. sativa</i>. The selfish allele <i>S13</i>^<i>l</i> in the <i>S13</i> locus impaired male fertility, discriminately eliminating pollens containing the allele <i>S13</i>^<i>s</i> from <i>O. sativa</i> in heterozygotes (<i>S13</i>^<i>s</i>/<i>S13</i>^<i>l</i>). Genetic analysis revealed that a gene encoding a chromatin-remodeling factor (CHR) is involved in this phenomenon and a variety of <i>O. sativa</i> owns the truncated gene <i>OsCHR745</i>, whereas its homologue <i>OlCHR</i> has a complete structure in <i>O. longistaminata</i>. CRISPR-Cas9-mediated loss of function mutants restored fertility in hybrids. African cultivated rice, which naturally lacks the <i>OlCHR</i> homologue, is compatible with both <i>S13</i>^<i>s</i> and <i>S13</i>^<i>l</i> carriers. These results suggest that <i>OlCHR</i> is a Killer gene, which leads to reproductive isolation.