scholarly journals Ancestral and neo‐sex chromosomes contribute to population divergence in a dioecious plant

Evolution ◽  
2019 ◽  
Vol 74 (2) ◽  
pp. 256-269 ◽  
Author(s):  
Felix E.G. Beaudry ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright
2019 ◽  
Author(s):  
Felix E.G. Beaudry ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright

ABSTRACTEmpirical evidence from several animal groups suggests that sex chromosomes may disproportionately contribute to reproductive isolation. This occurs particularly when sex chromosomes are associated with turnover of sex determination systems resulting from structural rearrangements to the sex chromosomes. We investigated these predictions in the dioecious plant Rumex hastatulus, which is comprised of populations of two sex chromosome cytotypes. Using population genomic analyses, we investigated the demographic history of R. hastatulus and explored the contributions of ancestral and neo-sex chromosomes to population genetic divergence. Our study revealed that the cytotypes represented genetically divergent populations with evidence for historical but not contemporary gene flow between them. In agreement with classical predictions, we found that the ancestral X chromosome was disproportionately divergent compared with the rest of the genome. Excess differentiation was also observed on the Y chromosome, even when using measures of differentiation that control for differences in effective population size. Our estimates of the timing of the origin of the neo-sex chromosomes in R. hastatulus are coincident with cessation of gene flow, suggesting that the chromosomal fusion event that gave rise to the origin of the XYY cytotype may have also been a key driver of reproductive isolation.


Genome ◽  
2002 ◽  
Vol 45 (4) ◽  
pp. 745-751 ◽  
Author(s):  
Sachihiro Matsunaga ◽  
Fumi Yagisawa ◽  
Maki Yamamoto ◽  
Wakana Uchida ◽  
Shunsuke Nakao ◽  
...  

Conserved domains of two types of LTR retrotransposons, Ty1–copia- and Ty3–gypsy-like retrotransposons, were isolated from the dioecious plant Silene latifolia, whose sex is determined by X and Y chromosomes. Southern hybridization analyses using these retrotransposons as probes resulted in identical patterns from male and female genomes. Fluorescence in situ hybridization indicated that these retrotransposons do not accumulate specifically in the sex chromosomes. These results suggest that recombination between the sex chromosomes of S. latifolia has not been severely reduced. Conserved reverse transcriptase regions of Ty1–copia-like retrotransposons were isolated from 13 different Silene species and classified into two major families. Their categorization suggests that parallel divergence of the Ty1–copia-like retrotransposons occurred during the differentiation of Silene species. Most functional retrotransposons from three dioecious species, S. latifolia, S. dioica, and S. diclinis, fell into two clusters. The evolutionary dynamics of retrotransposons implies that, in the genus Silene, dioecious species evolved recently from gynodioecious species.Key words: retrotransposon, dioecious plant, sex chromosome.


2014 ◽  
Author(s):  
Josh Hough ◽  
J Arvid Agren ◽  
Spencer CH Barrett ◽  
Stephen I Wright

The coordination between nuclear and organellar genes is essential to many aspects of eukaryotic life, including basic metabolism, energy production, and ultimately, organismal fitness. Whereas nuclear genes are bi-parentally inherited, mitochondrial and chloroplast genes are almost exclusively maternally inherited, and this asymmetry may lead to a bias in the chromosomal distribution of nuclear genes whose products act in the mitochondria or chloroplasts. In particular, because X-linked genes have a higher probability of co-transmission with organellar genes (2/3) compared to autosomal genes (1/2), selection for co-adaptation has been predicted to lead to an over-representation of nuclear-mitochondrial (N-mt) or nuclear-chloroplast (N-cp) genes on the X chromosome relative to autosomes. In contrast, the occurrence of sexually antagonistic organellar mutations might lead to selection for movement of cyto-nuclear genes from the X chromosome to autosomes to reduce male mutation load. Recent broad-scale comparative studies of N-mt distributions in animals have found evidence for these hypotheses in some species, but not others. Here, we use transcriptome sequences to conduct the first study of the chromosomal distribution of cyto-nuclear interacting genes in a plant species with sex chromosomes (Rumex hastatulus; Polygonaceae). We found no evidence of under- or over-representation of either N-mt or N-cp genes on the X chromosome, and thus no support for either the co-adaptation or the sexual-conflict hypothesis. We discuss how our results from a species with recently evolved sex chromosomes fit into an emerging picture of the evolutionary forces governing the chromosomal distribution of N-mt and N-cp genes.


2021 ◽  
Author(s):  
Joanna L Rifkin ◽  
Solomiya Hnatovzka ◽  
Meng Yuan ◽  
Bianca M Sacchi ◽  
Baharul I Choudhury ◽  
...  

There is growing evidence across diverse taxa for sex differences in the genomic landscape of recombination, but the causes and consequences of these differences remain poorly understood. Strong recombination landscape dimorphism between the sexes could have important implications for the dynamics of sex chromosome evolution and turnover because low recombination in the heterogametic sex can help favour the spread of sexually antagonistic alleles. Here, we present a sex-specific linkage map and revised genome assembly of Rumex hastatulus, representing the first characterization of sex differences in recombination landscape in a dioecious plant. We provide evidence for strong sex differences in recombination, with pericentromeric regions of highly suppressed recombination in males that cover over half of the genome. These differences are found on autosomes as well as sex chromosomes, suggesting that pre-existing differences in recombination may have contributed to sex chromosome formation and divergence. Analysis of segregation distortion suggests that haploid selection due to pollen competition occurs disproportionately in regions with low male recombination. Our results are consistent with the hypothesis that sex differences in the recombination landscape contributed to the formation of a large heteromorphic pair of sex chromosomes, and that pollen competition is an important determinant of recombination dimorphism.


2014 ◽  
Vol 6 (9) ◽  
pp. 2439-2443 ◽  
Author(s):  
Josh Hough ◽  
J. Arvid Ågren ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright

2017 ◽  
Author(s):  
Paris Veltsos ◽  
Kate E. Ridout ◽  
Melissa A. Toups ◽  
Santiago C. González-Martínez ◽  
Aline Muyle ◽  
...  

AbstractSuppressed recombination around a sex-determining locus allows divergence between homologous sex chromosomes and the functionality of their genes. Here, we reveal patterns of the earliest stages of sex-chromosome evolution in the diploid dioecious herb Mercurialis annua on the basis of cytological analysis, de novo genome assembly and annotation, genetic mapping, exome resequencing of natural populations, and transcriptome analysis. Both genetic mapping and exome resequencing of individuals across the species range independently identified the largest linkage group, LG1, as the sex chromosome. Although the sex chromosomes of M. annua are karyotypically homomorphic, we estimate that about a third of the Y chromosome has ceased recombining, a region containing 568 transcripts and spanning 22.3 cM in the corresponding female map. Patterns of gene expression hint at the possible role of sexually antagonistic selection in having favored suppressed recombination. In total, the genome assembly contained 34,105 expressed genes, of which 10,076 were assigned to linkage groups. There was limited evidence of Y-chromosome degeneration in terms of gene loss and pseudogenization, but sequence divergence between the X and Y copies of many sex-linked genes was higher than between M. annua and its dioecious sister species M. huetii with which it shares a sex-determining region. The Mendelian inheritance of sex in interspecific crosses, combined with the other observed pattern, suggest that the M. annua Y chromosome has at least two evolutionary strata: a small old stratum shared with M. huetii, and a more recent larger stratum that is probably unique to M. annua and that stopped recombining about one million years ago.Article summaryPlants that evolved separate sexes (dioecy) recently are ideal models for studying the early stages of sex-chromosome evolution. Here, we use karyological, whole genome and transcriptome data to characterize the homomorphic sex chromosomes of the annual dioecious plant Mercurialis annua. Our analysis reveals many typical hallmarks of dioecy and sex-chromosome evolution, including sex-biased gene expression and high X/Y sequence divergence, yet few premature stop codons in Y-linked genes and very little outright gene loss, despite 1/3 of the sex chromosome having ceased recombination in males. Our results confirm that the M. annua species complex is a fertile system for probing early stages in the evolution of sex chromosomes.


1993 ◽  
Vol 239 (1-2) ◽  
pp. 219-224 ◽  
Author(s):  
Boris Vyskot ◽  
Alejandro Araya ◽  
Jacky Veuskens ◽  
Ioan Negrutiu ◽  
Armand Mouras

2013 ◽  
Vol 5 (4) ◽  
pp. 769-782 ◽  
Author(s):  
Pavlina Steflova ◽  
Viktor Tokan ◽  
Ivan Vogel ◽  
Matej Lexa ◽  
Jiri Macas ◽  
...  

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 291
Author(s):  
Peta Hill ◽  
Foyez Shams ◽  
Christopher P. Burridge ◽  
Erik Wapstra ◽  
Tariq Ezaz

Sex determination directs development as male or female in sexually reproducing organisms. Evolutionary transitions in sex determination have occurred frequently, suggesting simple mechanisms behind the transitions, yet their detail remains elusive. Here we explore the links between mechanisms of transitions in sex determination and sex chromosome evolution at both recent and deeper temporal scales (<1 Myr; ~79 Myr). We studied a rare example of a species with intraspecific variation in sex determination, Carinascincus ocellatus, and a relative, Liopholis whitii, using c-banding and mapping of repeat motifs and a custom Y chromosome probe set to identify the sex chromosomes. We identified both unique and conserved regions of the Y chromosome among C. ocellatus populations differing in sex determination. There was no evidence for homology of sex chromosomes between C. ocellatus and L. whitii, suggesting independent evolutionary origins. We discuss sex chromosome homology between members of the subfamily Lygosominae and propose links between sex chromosome evolution, sex determination transitions, and karyotype evolution.


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