Molecular adaptation of rbcL in the heterophyllous aquatic plant Potamogeton.
Molecular adaptation of rbcL in the heterophyllous aquatic plant Potamogeton.
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DOI：
10.1371/journal.pone.0004633
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
Kosuge, Keiko
中科院分区：
文献类型：
--
作者：
Iida, Satoko;Miyagi, Atsuko;Aoki, Seishiro;Ito, Motomi;Kadono, Yasuro;Kosuge, Keiko
异叶水生植物表现出显著的表型可塑性。它们通过产生不同类型的叶子来适应环境变化：水下叶、漂浮叶和陆生叶。相比之下，同叶植物只产生淹没在水中的叶子，完全生长在水下。在选择压力的作用下，异叶植物和水下同叶植物的进化改变了物种特有的光合作用条件，但对习性的进化结果知之甚少。最近的进化分析表明，在大多数陆地植物谱系中，编码RuBisCO催化亚基的叶绿体基因rbcL在正选择下进化。为了研究与异缘性或同缘性相关的适应性进化过程，我们分析了生态多样性水生植物日本薯蓣rbcL序列的正选择。密码子替换模型的系统发育和最大似然分析表明，Potamogeton rbcL是在达尔文的积极选择下进化的。在分枝位点模型中，正选择只在异叶系中起作用，而在同叶系中不起作用。这表明该叶绿体基因在异叶系的选择压力大于同叶系的选择压力。在RbcL的四级结构中，有12个重要的氨基酸被替换，其中两个（残基225和281）被确定为潜在的正选择。我们的分析没有显示氨基酸替换与异叶性或同叶性之间的确切关系，但揭示了谱系特异性的正选择作用于Potamogeton rbcL。异叶和同叶植物不同的生态条件对光合系统施加了不同的选择压力。RbcL中氨基酸替换量的增加可能反映了RuBisCO在不同生态条件下的不断微调。
Heterophyllous aquatic plants show marked phenotypic plasticity. They adapt to environmental changes by producing different leaf types: submerged, floating and terrestrial leaves. By contrast, homophyllous plants produce only submerged leaves and grow entirely underwater. Heterophylly and submerged homophylly evolved under selective pressure modifying the species-specific optima for photosynthesis, but little is known about the evolutionary outcome of habit. Recent evolutionary analyses suggested that rbcL, a chloroplast gene that encodes a catalytic subunit of RuBisCO, evolves under positive selection in most land plant lineages. To examine the adaptive evolutionary process linked to heterophylly or homophylly, we analyzed positive selection in the rbcL sequences of ecologically diverse aquatic plants, Japanese Potamogeton. Phylogenetic and maximum likelihood analyses of codon substitution models indicated that Potamogeton rbcL has evolved under positive Darwinian selection. The positive selection has operated specifically in heterophyllous lineages but not in homophyllous ones in the branch-site models. This suggests that the selective pressure on this chloroplast gene was higher for heterophyllous lineages than for homophyllous lineages. The replacement of 12 amino acids occurred at structurally important sites in the quaternary structure of RbcL, two of which (residue 225 and 281) were identified as potentially under positive selection. Our analysis did not show an exact relationship between the amino acid replacements and heterophylly or homophylly but revealed that lineage-specific positive selection acted on the Potamogeton rbcL. The contrasting ecological conditions between heterophyllous and homophyllous plants have imposed different selective pressures on the photosynthetic system. The increased amino acid replacement in RbcL may reflect the continuous fine-tuning of RuBisCO under varying ecological conditions.
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FROSTCHRISTENSEN, H;SANDJENSEN, K
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