C4 photosynthesis evolved in grasses via parallel adaptive genetic changes
C4 photosynthesis evolved in grasses via parallel adaptive genetic changes
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DOI：
10.1016/j.cub.2007.06.036
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发表时间：
2007-07-17
期刊：
影响因子：
9.2
通讯作者：
Besnard, Guillaume
中科院分区：
文献类型：
--
作者：
Christin, Pascal-Antoine;Salamin, Nicolas;Besnard, Guillaume
表型趋同是一种广泛存在的进化现象。然而，负责的分子机制仍然是未知的，主要是因为涉及的基因没有被确定。一个众所周知的生理趋同的例子是C-4光合途径，它独立进化了45次以上[1]。在这里，我们解决的问题的C-4收敛表型在禾本科（禾本科）重建的进化历史的基因编码的C-4关键酶，磷酸烯醇式丙酮酸羧化酶（PEPC）的分子基础。PEPC基因属于编码不同亚型的多基因家族，其中只有一个参与C-4光合作用[2]。通过系统发育分析，我们发现，草C-4 PEPC出现至少8次独立于相同的非C-4 PEPC。21个氨基酸的进化下积极的选择和收敛到相似或相同的氨基酸在大多数的草C-4 PEPC谱系。这是第一次记录如此高水平的分子趋同进化，说明了进化的可重复性。这些氨基酸负责将所有C-4 PEPC分组在一起的强系统发育偏倚。检测到的C-4特异性氨基酸必须是C-4 PEPC酶特性所必需的，它们的鉴定为作物中C-4途径的工程设计开辟了新的途径。
Phenotypic convergence is a widespread and well-recognized evolutionary phenomenon. However, the responsible molecular mechanisms remain often unknown mainly because the genes involved are not identified. A well-known example of physiological convergence is the C-4 photosynthetic pathway, which evolved independently more than 45 times [1]. Here, we address the question of the molecular bases of the C-4 convergent phenotypes in grasses (Poaceae) by reconstructing the evolutionary history of genes encoding a C-4 key enzyme, the phosphoenolpyruvate carboxylase (PEPC). PEPC genes belong to a multigene family encoding distinct isoforms of which only one is involved in C-4 photosynthesis [2]. By using phylogenetic analyses, we showed that grass C-4 PEPCs appeared at least eight times independently from the same non-C-4 PEPC. Twenty-one amino acids evolved under positive selection and converged to similar or identical amino acids in most of the grass C-4 PEPC lineages. This is the first record of such a high level of molecular convergent evolution, illustrating the repeatability of evolution. These amino acids were responsible for a strong phylogenetic bias grouping all C-4 PEPCs together. The C-4-specific amino acids detected must be essential for C-4 PEPC enzymatic characteristics, and their identification opens new avenues for the engineering of the C-4 pathway in crops.