Genome Sequencing Reveals the Origin of the Allotetraploid Arabidopsis suecica.
Genome Sequencing Reveals the Origin of the Allotetraploid Arabidopsis suecica.
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DOI：
10.1093/molbev/msw299
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发表时间：
2017-04-01
影响因子：
10.7
通讯作者：
Nordborg M
中科院分区：
文献类型：
--
作者：
Novikova PY;Tsuchimatsu T;Simon S;Nizhynska V;Voronin V;Burns R;Fedorenko OM;Holm S;Säll T;Prat E;Marande W;Castric V;Nordborg M
多倍体是瞬时物种形成的一个例子，它涉及形成与亲本物种不相容的新细胞型。由于新的多倍体个体可能很少，除非多倍体能够通过自交或无性繁殖繁殖，否则不太可能建立新的物种。相反，自交(或无性繁殖)使多倍体物种有可能起源于单个个体--这是一种真正的物种形成事件。目前尚不清楚这种情况会在多大程度上发生。在这里，我们考虑到拟南芥的起源，它是拟南芥和拟南芥之间的自交异源多倍体，到目前为止一直被认为是唯一起源的例子。基于对15个天然猪草种质的全基因组重测序，我们确定了与亲本物种普遍存在的共享多态，从而最终拒绝了一个独特的起源，而倾向于多个创始个体。我们进一步估计，该物种起源于最后一次冰川盛期之后的东欧或欧亚大陆中部(而不是瑞典，顾名思义)。最后，对甜菜自交不亲和基因座的注释表明，这两个基因座都携带非功能等位基因。从自交沙打旺遗传的座位固定为祖先的非功能等位基因，而从异交沙打旺遗传的座位固定为新的功能丧失的等位基因。此外，从A.thaliana遗传的等位基因被预测在转录上使从A.arenosa遗传的等位基因沉默，这表明自交不亲和性的丧失可能是瞬间的。
Polyploidy is an example of instantaneous speciation when it involves the formation of a new cytotype that is incompatible with the parental species. Because new polyploid individuals are likely to be rare, establishment of a new species is unlikely unless polyploids are able to reproduce through self-fertilization (selfing), or asexually. Conversely, selfing (or asexuality) makes it possible for polyploid species to originate from a single individual—a bona fide speciation event. The extent to which this happens is not known. Here, we consider the origin of Arabidopsis suecica, a selfing allopolyploid between Arabidopsis thaliana and Arabidopsis arenosa, which has hitherto been considered to be an example of a unique origin. Based on whole-genome re-sequencing of 15 natural A. suecica accessions, we identify ubiquitous shared polymorphism with the parental species, and hence conclusively reject a unique origin in favor of multiple founding individuals. We further estimate that the species originated after the last glacial maximum in Eastern Europe or central Eurasia (rather than Sweden, as the name might suggest). Finally, annotation of the self-incompatibility loci in A. suecica revealed that both loci carry non-functional alleles. The locus inherited from the selfing A. thaliana is fixed for an ancestral non-functional allele, whereas the locus inherited from the outcrossing A. arenosa is fixed for a novel loss-of-function allele. Furthermore, the allele inherited from A. thaliana is predicted to transcriptionally silence the allele inherited from A. arenosa, suggesting that loss of self-incompatibility may have been instantaneous.