RATES AND PATTERNS OF CHLOROPLAST DNA EVOLUTION
RATES AND PATTERNS OF CHLOROPLAST DNA EVOLUTION
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DOI：
10.1073/pnas.91.15.6795
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发表时间：
1994-07-19
影响因子：
11.1
通讯作者：
MORTON, BR
中科院分区：
文献类型：
--
作者：
CLEGG, MT;GAUT, BS;MORTON, BR
植物叶绿体基因组(CpDNA)一直是植物分子进化和系统学研究的热点。该基因组的几个特征为分子进化分析提供了便利。首先，基因组很小，是细胞DNA的丰富组成部分。其次，叶绿体基因组已在分子水平上得到了广泛的表征，为比较进化研究提供了基础信息。第三，核苷酸替换的速度相对较慢，因此为在进化的深层水平上研究植物系统发育提供了适当的解决窗口。尽管进化速度保守，基因含量相对稳定，但比较分子分析揭示了复杂的突变变化模式。CpDNA的非编码区通过插入/缺失改变而发生分歧，这种改变有时与位点有关。编码基因表现出不同的密码子偏向模式，这似乎违反了某些进化模型的平衡假设。分子变化的速度在不同的植物科和目之间往往是不同的，这违反了简单的分子钟的假设。最后，蛋白质编码基因显示的氨基酸变化模式似乎取决于蛋白质结构，这些模式可能揭示结构/功能关系的微妙方面。只有对分子序列的比较研究才能揭示这种潜在的复杂性。对分子变化的复杂性的完整描述对于充分理解进化变化的机制和制定现实的突变过程模型是必不可少的。
The chloroplast genome (cpDNA) of plants has been a focus of research in plant molecular evolution and systematics. Several features of this genome have facilitated molecular evolutionary analyses. First, the genome is small and constitutes an abundant component of cellular DNA. Second, the chloroplast genome has been extensively characterized at the molecular level providing the basic information to support comparative evolutionary research. And third, rates of nucleotide substitution are relatively slow and therefore provide the appropriate window of resolution to study plant phylogeny at deep levels of evolution. Despite a conservative rate of evolution and a relatively stable gene content, comparative molecular analyses reveal complex patterns of mutational change. Non-coding regions of cpDNA diverge through insertion/deletion changes that are sometimes site dependent. Coding genes exhibit different patterns of codon bias that appear to violate the equilibrium assumptions of some evolutionary models. Rates of molecular change often vary among plant families and orders in a manner that violates the assumption of a simple molecular clock. Finally, protein-coding genes exhibit patterns of amino acid Change that appear to depend on protein structure, and these patterns may reveal subtle aspects of structure/function relationships. Only comparative studies of molecular sequences have the resolution to reveal this underlying complexity. A complete description of the complexity of molecular change is essential to a full understanding of the mechanisms of evolutionary change and in the formulation of realistic models of mutational processes.