Incongruent patterns of local and global genome size evolution in cotton
Incongruent patterns of local and global genome size evolution in cotton
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DOI：
10.1101/gr.2673204
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发表时间：
2004-08-01
期刊：
影响因子：
7
通讯作者：
Wendel, JF
中科院分区：
文献类型：
--
作者：
Grover, CE;Kim, HR;Wendel, JF
植物的基因组大小在几个数量级上变化，反映了差异作用的局部和全局力量的组合，例如indel积累和转座因子增殖或去除的偏差。为了深入了解这些和其他力的相对作用，我们比较了异源多倍体棉花物种陆地棉的两个共存基因组（A（T）和D-T）的纤维素合成酶基因CesA 1周围类似于105 kb的连续序列。这两个基因组的大小大约相差两倍，它们在大约500 - 1000万年前（Mya）从一个共同的祖先分化出来，并在多倍体形成时（类似于1 -2 Mya）在同一个细胞核中重新团聚。基因的内容，顺序和间距在很大程度上是保守的两个基因组之间，虽然一些转座因子和一个单一的叶绿体DNA片段区分这两个同源。在基因间和基因区域中序列保守性都很高，在两个基因组中检测到14个保守基因，每7.5 kb产生1个基因的密度。与DNA含量的两倍总体差异相反，对于该105-kb区域没有观察到大小的差异，并且检测到区分两种同源异型BAC的555个插入缺失，其在数量和聚集体大小上大致相等地分布在A（T）和D-T之间。这些数据表明，在这种系统发育尺度上的基因组大小进化主要不是由不同基因组区域和组分之间一致运作的机制引起的;相反，DNA含量的双重总体差异必须反映基因岛之间或大部分无基因区域之间的局部运作力。
Genome sizes in plants vary over several orders of magnitude, reflecting a combination of differentially acting local and global forces such as biases in indel accumulation and transposable element proliferation or removal. To gain insight into the relative role of these and other forces, similar to105 kb of contiguous sequence surrounding the cellulose synthase gene CesAl was compared for the two coresident genomes (A(T) and D-T) of the allopolyploid cotton species, Gossypium hirsutum. These two genomes differ approximately twofold in size, having diverged from a common ancestor similar to5-10 million years ago (Mya) and been reunited in the same nucleus at the time of polyploid formation, similar to1-2 Mya. Gene content, order, and spacing are largely conserved between the two genomes, although a few transposable elements and a single cpDNA fragment distinguish the two homoeologs. Sequence conservation is high in both intergenic and genic regions, with 14 conserved genes detected in both genomes yielding a density of 1 gene every 7.5 kb. In contrast to the twofold overall difference in DNA content, no disparity in size was observed for this 105-kb region, and 555 indels were detected that distinguish the two homoeologous BACs, approximately equally distributed between A(T) and D-T in number and aggregate size. The data demonstrate that genome size evolution at this phylogenetic scale is not primarily caused by mechanisms that operate uniformly across different genomic regions and components; instead, the twofold overall difference in DNA content must reflect locally operating forces between gene islands or in largely gene-free regions.