SRA

Chromosomal sex determination is common in many species. Dioecious plants, unlike many gonochoristic animals, evolved independently in different lineages from functional hermaphrodite ancestors. So far, two evolutionary pathways to genetic sex determination have been well characterized. Systems with two-locus, male-determining and female-suppressing factors, located in separate, but closely linked sex chromosome regions, have been uncovered by genomic studies in several plants. Alternatively, the two mutations may interact such that one spreads throughout the species, leaving a single sex-determining gene. Single gene situations can often facilitate a turnover event creating a sex-determining locus in a new genomic location. In kiwifruit, sex (gender) is determined by two Y-linked factors. Across a wide variety of Actinidia species, males produce more flowers than females, after a shorter juvenile phase. This conservation across species might suggest that these sexual dimorphisms were established before the divergence of Actinidia species, perhaps after a non-recombining MSY evolved to preserve advantageous combinations of sex determining factors and sexually antagonistic genes.