Persimmon sex ratio distortion
In contrast to the recent understanding of the genomic context in plant sex chromosomes, the functional contribution of the genes in sex chromosomes remains little known. They were classically thought to be related to sexual dimorphism, which is beneficial to male or female functions, including the segregation ratios. In this study, we focused on the functional evolution of the sex ratio distortion-related locus Half Male Sterile/Inviable (HaMSter), which is located in the short sex-linked region in diploid persimmon (Diospyros lotus). The expression of HaMSter is necessary for post-zygotic cellularization during endosperm development. Notably, HaMSter is expressed in an X-allele-specific manner, with half of the maternal X-alleles of HaMSter randomly inactivated, resulting in female-biased segregation. Genome-wide DNA methylome analyses revealed endosperm-specific DNA hyper-methylation, especially in the X-linked region. The maintenance/release of this hyper-methylation is linked to the random half inactivation of HaMSter, which determines the sex ratio distortion pattern.