Evolution of Sex Chromosomes and Gynoecium Suppression in Plants

Abstract

White campion (Silene latifolia, Caryophyllaceae) is a classical model species for studies of sex determination and sex chromosome evolution in dioecious plants. Deletion mapping in this species revealed the presence of two Y-linked sex determining genes̶the stamen promoting factor (SPF) gene and a gynoecium suppressing factor (GSF), which inspired the development of the classic ‘two genes’ model for dioecy evolution. We recently identified a Y-linked GSFY gene that encodes a CLAVATA3 homolog and causes gynoecium suppression in S. latifolia via WUSCHEL-CLAVATA feedback loop. Interestingly, the WUSCHEL homolog in S. latifolia (SlWUS1) is also sex-linked and both GSFY and SlWUS1 are located in the oldest part of the sex chromosomes, suggesting that selection to prevent recombination between these genes may have contributed to the origination of sex chromosomes in this species. The WUS-CLV3 pathway is also involved in the sexual differentiation of gynoecium development in kiwifruits and melon, indicating that this pathway plays central role in gynoecium suppression in dioecious and monoecious plants.