BACKGROUND The CO2-concentrating mechanism associated to Crassulacean acid metabolism (CAM) alters the catalytic context for Rubisco by increasing CO2 availability and provides an advantage in particular ecological conditions. We hypothesized about the existence of molecular changes linked to these particular adaptations in CAM Rubisco. We investigated molecular evolution of the Rubisco large (L-) subunit in 78 orchids and 144 bromeliads with C3 and CAM photosynthetic pathways. The sequence analyses were complemented with measurements of Rubisco kinetics in some species with contrasting photosynthetic mechanism and differing in the L-subunit sequence. RESULTS We identified potential positively selected sites and residues with signatures of co-adaptation. The implementation of a decision tree model related Rubisco specific variable sites to the leaf carbon isotopic composition of the species. Differences in the Rubisco catalytic traits found among C3 orchids and between strong CAM and C3 bromeliads suggested Rubisco had evolved in response to differing CO2 concentration. CONCLUSIONS The results revealed that the variability in the Rubisco L-subunit sequence in orchids and bromeliads is composed of coevolving sites under potential positive adaptive signal. The sequence variability was related to δ13C in orchids and bromeliads, however it could not be linked to the variability found in the kinetic properties of the studied species.

中文翻译：

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探索 C3 和 CAM 兰科和凤梨科中 Rubisco 的分子进化。


背景技术与景天酸代谢 (CAM) 相关的 CO2 浓缩机制通过增加 CO2 可用性来改变 Rubisco 的催化环境，并在特定的生态条件下提供优势。我们假设 CAM Rubisco 中存在与这些特殊适应相关的分子变化。我们研究了 78 种兰花和 144 种凤梨科植物中具有 C3 和 CAM 光合途径的 Rubisco 大 (L-) 亚基的分子进化。序列分析与一些具有对比光合机制和 L 亚基序列不同的物种的 Rubisco 动力学测量进行了补充。结果我们确定了具有共适应特征的潜在正选位点和残基。决策树模型的实施将 Rubisco 特定变量位点与该物种的叶碳同位素组成相关联。在 C3 兰花之间以及强 CAM 和 C3 凤梨科植物之间发现的 Rubisco 催化特性的差异表明 Rubisco 是为了响应不同的 CO2 浓度而进化的。结论 结果表明，兰花和凤梨科植物中 Rubisco L 亚基序列的变异性是由潜在正适应信号下的共同进化位点组成的。序列变异性与兰花和凤梨科植物中的 δ13C 有关，但与所研究物种的动力学特性中发现的变异性无关。