The Y chromosome of white campion: sexual dimorphism and beyond

White campion (Silene latifolia) is a dioecious plant with heteromorphic X and Y sex chromosomes. The Y chromosome contains key genes controlling the sexual dimorphism. In male plants, a filamentous structure replaces the pistil, while in female plants the stamens degenerate early in flower development. The white campion experimental system (latest review by Ainsworth et al., 1998) represents a suitable model in studying the organization and the evolution of an XY system in plants. The Y chromosome has been divided into four domains (Westergaard, 1958), harbouring distinct features: (Y^I) female suppression, containing the gynoecium suppression function (GSF); (Y^II) male promoting function(s), containing the stamen promoting function (SPF); (Y^III) male fertility functions; (Y^IV) pseudo-autosomal region ( Figure 1 ). Despite long-lasting interest in studies on sexual development in this species (Correns, 1928; Gedes and Thomson, 1889; Ruddat et al., 1991; van Nigtevecht, 1966; Westergaard, 1958; Winge, 1931), three main problems await proper answers or clarification: (1) the origin of dioecy and of the sex chromosomes among Silene species, (2) the morphological and molecular bases of sexual dimorphism and (3) the structural features of Y and X chromosomes. Figure 1 Functional and structural domains (I–IV) of the Y chromosome according to <xref ref-type="bibr" rid="ref5_31">Westergaard (1958)</xref>. Domains I and III were established based on Y deletion mutants with hermaphroditic and male sterile phenotypes, respectively. Domain II was positioned by default and in conformity with the female flower phenotype in XX plants. The pseudo autosomal region corresponds to the X—Y pairing domain during meiosis in wildtype male flowers. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203345993/16024350-317f-4ad0-98e6-6c8fb6b51324/content/fig5_1.tif"/>