Three tiers of genome evolution in reptiles.
Three tiers of genome evolution in reptiles.
复制标题
爬行动物基因组进化的三层。
DOI：
10.1093/icb/icn046
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发表时间：
2008
影响因子：
2.6
通讯作者：
Edwards,ScottV
中科院分区：
文献类型：
--
作者：
Organ,ChrisL;Moreno,RicardoGodínez;Edwards,ScottV
爬行动物基因组的表征对于理解爬行动物基因组的整体多样性和进化至关重要，因为爬行动物，包括鸟类，构成了爬行动物进化树的主要部分。为了更好地了解爬行动物基因组特征的进化和多样性，我们对短吻鳄（Alligator mississippiensis）和楔齿蜥（Sphenodon punctatus）的在线序列数据以及广泛的爬行动物物种的基因组大小和核型数据进行了比较分析。在全基因组和染色体层次的组织，我们发现，爬行动物基因组的大小分布是一致的模型，而基因组的分区，表现在微染色体和宏染色体的数量，似乎经历了早期的快速变化。在第三层基因组序列水平上，我们发现扬子鳄的外显子大小与鸡的外显子大小相匹配，特别是在101-200 bp的大小类别中。在301 bp-1 kb大小的外显子中也观察到一个小的尖峰，但更多的是为楔齿鲨。对于内含子，我们发现，爬行动物的成员有一个较大的比例内的101 bp-2 kb大小的类和较低的比例内的5-30 kb大小的类的内含子比哺乳动物。这些发现表明，爬行动物基因组进化的模式在基因组的三个层次上各不相同，这种模式与基因组进化的马赛克模型一致。
Characterization of reptilian genomes is essential for understanding the overall diversity and evolution of amniote genomes, because reptiles, which include birds, constitute a major fraction of the amniote evolutionary tree. To better understand the evolution and diversity of genomic characteristics in Reptilia, we conducted comparative analyses of online sequence data fromAlligator mississippiensis(alligator) andSphenodon punctatus(tuatara) as well as genome size and karyological data from a wide range of reptilian species. At the whole-genome and chromosomal tiers of organization, we find that reptilian genome size distribution is consistent with a model of continuous gradual evolution while genomic compartmentalization, as manifested in the number of microchromosomes and macrochromosomes, appears to have undergone early rapid change. At the sequence level, the third genomic tier, we find that exon size inAlligatoris distributed in a pattern matching that of exons inGallus(chicken), especially in the 101—200 bp size class. A small spike in the fraction of exons in the 301 bp—1 kb size class is also observed forAlligator, but more so forSphenodon. For introns, we find that members of Reptilia have a larger fraction of introns within the 101 bp–2 kb size class and a lower fraction of introns within the 5–30 kb size class than do mammals. These findings suggest that the mode of reptilian genome evolution varies across three hierarchical levels of the genome, a pattern consistent with a mosaic model of genomic evolution.