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向日葵倒位的突变负荷与倒位杂合性呈负相关。

Mutation Load in Sunflower Inversions Is Negatively Correlated with Inversion Heterozygosity.

机构信息

Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.

Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA.

出版信息

Mol Biol Evol. 2022 May 3;39(5). doi: 10.1093/molbev/msac101.

Abstract

Recombination is critical both for accelerating adaptation and purging deleterious mutations. Chromosomal inversions can act as recombination modifiers that suppress local recombination in heterozygotes and thus, under some conditions, are predicted to accumulate such mutations. In this study, we investigated patterns of recombination, transposable element abundance, and coding sequence evolution across the genomes of 1,445 individuals from three sunflower species, as well as within nine inversions segregating within species. We also analyzed the effects of inversion genotypes on 87 phenotypic traits to test for overdominance. We found significant negative correlations of long terminal repeat retrotransposon abundance and deleterious mutations with recombination rates across the genome in all three species. However, we failed to detect an increase in these features in the inversions, except for a modest increase in the proportion of stop codon mutations in several very large or rare inversions. Consistent with this finding, there was little evidence of overdominance of inversions in phenotypes that may relate to fitness. On the other hand, significantly greater load was observed for inversions in populations polymorphic for a given inversion compared to populations monomorphic for one of the arrangements, suggesting that the local state of inversion polymorphism affects deleterious load. These seemingly contradictory results can be explained by the low frequency of inversion heterozygotes in wild sunflower populations, apparently due to divergent selection and associated geographic structure. Inversions contributing to local adaptation represent ideal recombination modifiers, acting to facilitate adaptive divergence with gene flow, while largely escaping the accumulation of deleterious mutations.

摘要

重组对于加速适应和清除有害突变至关重要。染色体倒位可以作为重组修饰因子,抑制杂合子中的局部重组,因此在某些条件下,预计会积累这些突变。在这项研究中,我们调查了三个向日葵物种的 1445 个人的基因组中的重组、转座元件丰度和编码序列进化模式,以及在物种内分离的九个倒位中。我们还分析了倒位基因型对 87 个表型特征的影响,以检验超显性。我们发现,在所有三个物种中,长末端重复逆转录转座子丰度和有害突变与基因组中重组率之间存在显著的负相关。然而,我们没有发现这些特征在倒位中增加,除了在几个非常大和罕见的倒位中,终止密码子突变的比例略有增加。与这一发现一致的是,在与适应性相关的表型中,倒位的超显性证据很少。另一方面,与一个排列的单态群体相比,在一个给定的倒位多态性群体中观察到的倒位的显著更大负荷,这表明局部倒位多态性状态影响有害负荷。这些看似矛盾的结果可以用野生向日葵种群中倒位杂合子的低频率来解释,这显然是由于分歧选择和相关的地理结构。有助于局部适应的倒位代表理想的重组修饰因子,有利于与基因流一起进行适应性分歧,而在很大程度上避免了有害突变的积累。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/f219/9127631/334e104fc33e/msac101f1.jpg

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