The role of the X chromosome in sex determination revealed by the identification of a sex-determining gene GSFY in Silene latifolia

Abstract

Plants maintain genetic diversity through strategies such as “dioecy,” where male flowers (♂) and female flowers (♀) are borne on separate individuals. Many dioecious plants have sex chromosomes, and in the XY system, the Y chromosome has the gene determining maleness. Sex chromosomes evolved from a pair of autosomes, with the Y chromosome diverging over time to form heteromorphic sex chromosomes, where the X and Y differ in size. Silene latifolia, a member of the Caryophyllaceae family, is a model species for studying heteromorphic sex chromosomes. Its Y chromosome contains a large recombination suppression region (~500 Mb), complicating the identification of sex-determining genes. By analyzing these chromosomes, the authors identified Gynoecium suppressing function on Y (GSFY), a gene that suppresses pistil development. GSFY was found to be an ortholog of the CLAVATA3 gene in Arabidopsis thaliana, involved in pistil reduction. Moreover, it was found that during the evolution of sex chromosomes, the X copy of the CLAVATA3 ortholog became nonfunctional, while the WUSCHEL ortholog, which is involved in pistil development, was lost from the Y chromosome but retained on the X chromosome. These findings suggest the X chromosome plays a role in sex determination, providing new insights into the evolution of plant sex chromosomes.