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石竹目植物祖先质体基因组的重建揭示了基因组重排、重复序列和核苷酸替换率之间的相关性。

Reconstruction of the ancestral plastid genome in Geraniaceae reveals a correlation between genome rearrangements, repeats, and nucleotide substitution rates.

机构信息

Department of Integrative Biology, University of Texas, Austin.

出版信息

Mol Biol Evol. 2014 Mar;31(3):645-59. doi: 10.1093/molbev/mst257. Epub 2013 Dec 12.

Abstract

Geraniaceae plastid genomes are highly rearranged, and each of the four genera already sequenced in the family has a distinct genome organization. This study reports plastid genome sequences of six additional species, Francoa sonchifolia, Melianthus villosus, and Viviania marifolia from Geraniales, and Pelargonium alternans, California macrophylla, and Hypseocharis bilobata from Geraniaceae. These genome sequences, combined with previously published species, provide sufficient taxon sampling to reconstruct the ancestral plastid genome organization of Geraniaceae and the rearrangements unique to each genus. The ancestral plastid genome of Geraniaceae has a 4 kb inversion and a reduced, Pelargonium-like small single copy region. Our ancestral genome reconstruction suggests that a few minor rearrangements occurred in the stem branch of Geraniaceae followed by independent rearrangements in each genus. The genomic comparison demonstrates that a series of inverted repeat boundary shifts and inversions played a major role in shaping genome organization in the family. The distribution of repeats is strongly associated with breakpoints in the rearranged genomes, and the proportion and the number of large repeats (>20 bp and >60 bp) are significantly correlated with the degree of genome rearrangements. Increases in the degree of plastid genome rearrangements are correlated with the acceleration in nonsynonymous substitution rates (dN) but not with synonymous substitution rates (dS). Possible mechanisms that might contribute to this correlation, including DNA repair system and selection, are discussed.

摘要

牻牛儿苗科质体基因组高度重排,而且该科中已测序的四个属都具有独特的基因组结构。本研究报道了Geraniales 中的 6 个附加种,即佛兰科 Sonchifolia、Melianthus villosus 和 Viviania marifolia,以及 Geraniaceae 中的 Pelargonium alternans、California macrophylla 和 Hypseocharis bilobata 的质体基因组序列。这些基因组序列与之前发表的物种相结合,为重建牻牛儿苗科的质体基因组祖先组织以及每个属特有的重排提供了足够的分类群采样。牻牛儿苗科的祖先质体基因组具有 4kb 的倒位和缩小的、类似 Pelargonium 的小单拷贝区。我们的祖先基因组重建表明,在牻牛儿苗科的茎分支中发生了一些较小的重排,然后每个属都发生了独立的重排。基因组比较表明,一系列反向重复边界的移动和倒位在家族基因组结构的形成中发挥了重要作用。重复序列的分布与重排基因组中的断点密切相关,大重复序列(>20bp 和>60bp)的比例和数量与基因组重排的程度显著相关。质体基因组重排程度的增加与非同义替换率(dN)的加速有关,但与同义替换率(dS)无关。讨论了可能导致这种相关性的机制,包括 DNA 修复系统和选择。

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