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Article

A Comparison of Selective Pressures in Plant X-Linked and Autosomal Genes

Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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Genes 2018, 9(5), 234; https://doi.org/10.3390/genes9050234
Received: 31 March 2018 / Revised: 23 April 2018 / Accepted: 26 April 2018 / Published: 3 May 2018
(This article belongs to the Special Issue The Evolutionary Life Cycle of Sex Chromosomes)
Selection is expected to work differently in autosomal and X-linked genes because of their ploidy difference and the exposure of recessive X-linked mutations to haploid selection in males. However, it is not clear whether these expectations apply to recently evolved sex chromosomes, where many genes retain functional X- and Y-linked gametologs. We took advantage of the recently evolved sex chromosomes in the plant Silene latifolia and its closely related species to compare the selective pressures between hemizygous and non-hemizygous X-linked genes as well as between X-linked genes and autosomal genes. Our analysis, based on over 1000 genes, demonstrated that, similar to animals, X-linked genes in Silene evolve significantly faster than autosomal genes—the so-called faster-X effect. Contrary to expectations, faster-X divergence was detectable only for non-hemizygous X-linked genes. Our phylogeny-based analyses of selection revealed no evidence for faster adaptation in X-linked genes compared to autosomal genes. On the other hand, partial relaxation of purifying selection was apparent on the X-chromosome compared to the autosomes, consistent with a smaller genetic diversity in S. latifolia X-linked genes (πx = 0.016; πaut = 0.023). Thus, the faster-X divergence in S. latifolia appears to be a consequence of the smaller effective population size rather than of a faster adaptive evolution on the X-chromosome. We argue that this may be a general feature of “young” sex chromosomes, where the majority of X-linked genes are not hemizygous, preventing haploid selection in heterogametic sex. View Full-Text
Keywords: X-chromosome; faster-X effect; positive selection; purifying selection; population size X-chromosome; faster-X effect; positive selection; purifying selection; population size
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MDPI and ACS Style

Krasovec, M.; Nevado, B.; Filatov, D.A. A Comparison of Selective Pressures in Plant X-Linked and Autosomal Genes. Genes 2018, 9, 234. https://doi.org/10.3390/genes9050234

AMA Style

Krasovec M, Nevado B, Filatov DA. A Comparison of Selective Pressures in Plant X-Linked and Autosomal Genes. Genes. 2018; 9(5):234. https://doi.org/10.3390/genes9050234

Chicago/Turabian Style

Krasovec, Marc, Bruno Nevado, and Dmitry A. Filatov 2018. "A Comparison of Selective Pressures in Plant X-Linked and Autosomal Genes" Genes 9, no. 5: 234. https://doi.org/10.3390/genes9050234

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