Sex determination with homomorphic chromosomes in haploid plants: genetic determination of sex in moss genus Sphagnum
Most of land plants are cosexual, meaning that they produce male and female sexual organs on the same individual. However, some plant species are unisexual (dioecious) meaning that they have sexes on separate individuals. Dioecy is scattered across many taxonomic groups which suggests that it has evolved independently many times from a cosexual state. Although many of the dioecious species have genetic sex determination, the presence of proper sex chromosomes is fairly rare and only identified in ca. 50 species of angiosperms, of which half possess heteromorphic sex chromosomes. However, the crucial feature of sex chromosomes is not being heteromorphic but suppressed recombination in the sex-determining genome regions. Recent molecular genetic studies identified fully sex-linked markers and genes in dioecious plants which helps testing the genetic basis of sex determination in plants lacking cytologically heteromorphic sex chromosomes. Among land plants, bryophytes are generally known to possess heteromorphic sex chromosomes, but peat mosses (genus Sphagnum) are one of the groups in which small chromosomes with no obvious heteromorphy may represent sex chromosomes or harbour sex-associated genes. Several previous studies showed that sex linkage can be detected by identifying variants restricted to one sex. We aim at using state-of-the-art methods such as Whole Genome Resequencing (WGR) and RAD-sequencing to characterise the genetic determination of sex in peat mosses.