Abstract
The genus Silene includes a plethora of dioecious and gynodioecious species. Two species, Silene latifolia (white campion) and Silene dioica (red campion), are dioecious plants, having heteromorphic sex chromosomes with an XX/XY sex determination system. The X and Y chromosomes differ mainly in size, DNA content and posttranslational histone modifications. Although it is generally assumed that the sex chromosomes evolved from a single pair of autosomes, it is difficult to distinguish the ancestral pair of chromosomes in related gynodioecious and hermaphroditic plants. We designed an oligo painting probe enriched for X-linked scaffolds from currently available genomic data and used this probe on metaphase chromosomes of S. latifolia (2n = 24, XY), S. dioica (2n = 24, XY), and two gynodioecious species, S. vulgaris (2n = 24) and S. maritima (2n = 24). The X chromosome-specific oligo probe produces a signal specifically on the X and Y chromosomes in S. latifolia and S. dioica, mainly in the subtelomeric regions. Surprisingly, in S. vulgaris and S. maritima, the probe hybridized to three pairs of autosomes labeling their p-arms. This distribution suggests that sex chromosome evolution was accompanied by extensive chromosomal rearrangements in studied dioecious plants.
Highlights
The genus Silene is a model system for sex chromosome evolution, including about 700 species varying greatly in their mating system, ecology and sex determination (Bernasconi et al, 2009)
We designed an X chromosome-specific oligo probe enriched by X-linked scaffolds based on the S. latifolia female genome. We show that such technique is useful for the detection of discrete signals in sex chromosomes in S. latifolia and closely related S. dioica
Minor changes were observed in signal strength if the amount of oligo painting probe in S. vulgaris was increased
Summary
The genus Silene is a model system for sex chromosome evolution, including about 700 species varying greatly in their mating system, ecology and sex determination (Bernasconi et al, 2009). Two dioecious plants S. latifolia (24, XY) and S. dioica (24, XY) from Melandrium have heteromorphic sex chromosomes and sex determination similar to mammals (Ming et al, 2007; Charlesworth, 2016). As a result of suppressed recombination and accumulation of deleterious mutations, the sex chromosomes differ in their structure, function and gene density. As a result of accumulation of deleterious mutations, the Y chromosome is degenerated and the sex chromosomes may differ even within closely related species as demonstrated in human and chimpanzee (Hughes et al, 2010). Newly formed sex chromosomes show the same signs of sex chromosome evolutionary pathways, as described in Drosophila (Bachtrog et al, 2009) or stickleback species (Yoshida et al, 2014) in which the ancestral Y chromosome fused with an autosome
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