Missed opportunity

Abstract

<h3>Abstract</h3> Dioecy, a sexual system of single-sex (gynoecious/androecious) individuals, is rare in flowering plants. This rarity may be a result of the frequent transition from dioecy into systems with co-sex individuals. Here, we report potential molecular and genetic mechanisms that underlie the dissolution of dioecy to monoecy and andro(gyno)monoecy, based on multiscale genome-wide investigations of 150 accessions of <i>Diospyros oleifera</i>. All co-sex <i>D. oleifera</i> plants, including monoecious and andro(gyno)monoecious individuals, possessed the male determinant gene <i>OGI</i>, implying that genetic factors control gynoecia development in genetically male <i>D. oleifera</i>. In both single- and co-sex plants, female function was expressed in the presence of a genome-wide decrease in methylation levels, along with sexually distinct regulatory networks of smRNAs and their targets. Furthermore, a genome-wide association study (GWAS) identified a genomic region and a <i>DUF247</i> gene cluster strongly associated with the monoecious phenotype, as well as several regions that may contribute to andromonoecy. Collectively, our findings imply stable breakdown of the dioecious system in <i>D. oleifera</i>, presumably a result of the genomic features of the sex-linked region.