A new physical mapping approach refines the sex-determining gene positions on the Silene latifolia Y-chromosome

Abstract

Sex chromosomes are particularly interesting regions of the genome for both molecular genetics and evolutionary studies; yet, for most species, we lack basic information, such as the gene order along the chromosome. Because they lack recombination, Y-linked genes cannot be mapped genetically, leaving physical mapping as the only option for establishing the extent of synteny and homology with the X chromosome. Here, we developed a novel and general method for deletion mapping of non-recombining regions by solving “the travelling salesman problem”, and evaluate its accuracy using simulated datasets. Unlike the existing radiation hybrid approach, this method allows us to combine deletion mutants from different experiments and sources. We applied our method to a set of newly generated deletion mutants in the dioecious plant Silene latifolia and refined the locations of the sex-determining loci on its Y chromosome map.

Sex Determination by Two Y-Linked Genes in Garden Asparagus

“…The SOFF and aspTDF1 genes are not present on the homologous X region or elsewhere in the XX female genome. There is no evidence of repeated inversions leading to the formation of strata on the asparagus Y chromosome ( Figure 1E), as has been inferred for older and more degenerate plant sex chromosomes like Carica papaya (Wang et al, 2012) and Silene latifolia (Bergero et al, 2008;Kazama et al, 2016). However, the finding that aspTDF1 is not sex-linked in all dioecious Asparagus species (Harkess et al 2017, Murase et al, 2017Tsugama et al, 2017) indicates that gene content in the sexdetermination region, and indeed the molecular basis of sex determination, are evolving in the genus.…”

One Hundred Ways to Invent the Sexes: Theoretical and Observed Paths to Dioecy in Plants

“…The best known is the two-factor model (Figure 1b) (19,52), whose evolution should entail a dimorphic pathway (Figure 1) (35), and in which dioecy evolves from hermaphroditism via an intermediate sexual system, gynodioecy or androdioecy. Genetic evidence for two factors controlling dioecy has been found in some plant species (47,90,91). For example, in Silene (formerly Melandrium), deletions of the Y chromosome localized both M (male inducer) and supF (female suppressor) (Figure 2c) (47,91).…”

“…Genetic evidence for two factors controlling dioecy has been found in some plant species (47,90,91). For example, in Silene (formerly Melandrium), deletions of the Y chromosome localized both M (male inducer) and supF (female suppressor) (Figure 2c) (47,91). The recent progress in the identification of putative sex determinants in Asparagus officinalis (asparagus) and Actinidia spp.…”

Evolution of sex determination and heterogamety changes in sectionOtitesof the genusSilene

“…The difference might reflect the very different extents of the sex-determining nonrecombining regions. Species in section Melandrium have extensive non-recombining Y-linked regions, carrying large numbers of genes, including anther development genes essential for male fertility [45][46][47][48] and genes essential for anther development [46][47][48] . Given its numerous genes, and the lethality of YY genotypes (reviewed by Westergaard 45 ), the non-recombining regions of the S. latifolia Y-chromosome has probably undergone some degeneration, and there is direct evidence of this in S. latifolia 27,[49][50][51] .…”