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Article Dans Une Revue Genome Biology and Evolution Année : 2018

Disentangling the Causes for Faster-X Evolution in Aphids

Tiphaine Ouisse
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Pierre Nouhaud
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Christophe Battail

Résumé

The faster evolution of X chromosomes has been documented in several species, and results from the increased efficiency of selection on recessive alleles in hemizygous males and/or from increased drift due to the smaller effective population size of X chromosomes. Aphids are excellent models for evaluating the importance of selection in faster-X evolution because their peculiar life cycle and unusual inheritance of sex chromosomes should generally lead to equivalent effective population sizes for X and autosomes. Because we lack a high-density genetic map for the pea aphid, whose complete genome has been sequenced, we first assigned its entire genome to the X or autosomes based on ratios of sequencing depth in males (X0) to females (XX). Then, we computed nonsynonymous to synonymous substitutions ratios (dN/dS) for the pea aphid gene set and found faster evolution of X-linked genes. Our analyses of substitution rates, together with polymorphism and expression data, showed that relaxed selection is likely to be the greatest contributor to faster-X because a large fraction of X-linked genes are expressed at low rates and thus escape selection. Yet, a minor role for positive selection is also suggested by the difference between substitution rates for X and autosomes for male-biased genes (but not for asexual female-biased genes) and by lower Tajima’s D for X-linked compared with autosomal genes with highly male-biased expression patterns. This study highlights the relevance of organisms displaying alternative chromosomal inheritance to the understanding of forces shaping genome evolution.

Dates et versions

hal-03276874 , version 1 (02-07-2021)

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Citer

Julie Jaquiéry, Jean Peccoud, Tiphaine Ouisse, Fabrice Legeai, Nathalie Prunier-Leterme, et al.. Disentangling the Causes for Faster-X Evolution in Aphids. Genome Biology and Evolution, 2018, 10 (2), pp.507-520. ⟨10.1093/gbe/evy015⟩. ⟨hal-03276874⟩
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