Divergent solutions to convergent evolution: elucidating the molecular strategies for co-option of the NAD-malic enzyme for C4 biochemistry

趋同进化的不同解决方案：阐明 C4 生物化学中 NAD-苹果酸酶共同选择的分子策略

• 批准号: 528182088
• 负责人: Professorin Dr. Veronica Maurino
• 金额: --
• 依托单位: Abteilung Molekulare Pflanzenphysiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/528182088?language=en
• 关键词: Divergent; solutions; convergent; evolution; elucidating

Over the past 30 million years, the C4 pathway of photosynthesis has evolved as a carbon concentrating mechanism to reduce photorespiration, a highly energy consuming process that leads to the release of previously fixed CO2. The C4 trait is ecologically and agronomically important as C4 plants have a superior growth potential in warm environments and C4 species comprise the most productive cereal crops. C4 photosynthesis is concentrated in relatively few orders of flowering plants, where it has originated over 65 times independently, providing an example of the convergent evolution of a complex functional trait. Nevertheless, C4 photosynthesis can be carried out in different ways, as shown not only in variations in decarboxylation types but also in leaf anatomy and cellular ultrastructure. The C4 pathway has evolved via the co-option of multiple genes present in non-C4 ancestors. Convergence in the co-option and adaptation of genes for C4 photosynthesis is apparent in the carboxylation step. In contrast, divergence exists in the decarboxylation step. About 43 of the 65 C4-lineages contain species using the NADP-malic enzyme as primary decarboxylase, while NAD-malic enzyme (NAD-ME) is used in 20 lineages, 16 of which are eudicots. Apart from likely lower accessibility for co-option of NAD-ME, C4-NAD-ME was acquired from different gene lineages by separated species. Our recent work shows that the mechanism of co-option of NAD-ME for the C4 photosynthetic pathway differs from that of all other C4 proteins, most likely because NAD-ME functions mainly as a heterodimer. Our work also shows that there exists plasticity in the co-option of genes encoding NAD-ME subunits. In the Eudicots, NAD-ME was independently adopted for C4 photosynthesis in Caryophyllales and Brassicales species. C4-NAD-ME of two Brassicales species from different C4 lineages, presented similar molecular adaptations: (a) all NAD-ME genes α, β1 and β2 were affected by C4 evolution and (b) the β1-NAD-ME was co-opted for C4 metabolism. On the contrary, in a C4 specie of the Caryophyllales, an extra copy of the α-NAD-ME (α1) gene likely was adopted for its function in the C4 pathway. Therefore, biochemical convergence in C4-NAD-ME subtype species could be drawn through an alternative association of α and β subunits. These variations are another example of the plasticity of the components in a functional C4 photosynthetic pathway, supporting the possibility of installing the C4 machinery in a C3 host. In this project, using complementary biochemical and structural analysis we aim to clarify whether and to what extent the selection of different molecular adaptations by convergent evolution has produced analogous features in C4-NAD-ME in different eudicot families. Furthermore, we aim to bioengineer a C4-NAD-ME into the BSC mitochondria using mutant lines of A. thaliana NAD-ME to explore metabolic consequences and the possible implementation in C3 to C4 bioengineering approaches.

在过去的3000万年里，光合作用的C4途径已经演变为减少光呼吸的碳浓缩机制，光呼吸是一个高耗能的过程，导致先前固定的二氧化碳的释放。C4性状具有重要的生态和农学意义，因为C4植物在温暖的环境中具有优越的生长潜力，而且C4物种构成了产量最高的谷类作物。C4光合作用集中在相对较少的几个开花植物目中，在这些植物中，C4光合作用已经独立发生了65次以上，为复杂功能性状的收敛进化提供了一个例子。然而，C4光合作用可以通过不同的方式进行，这不仅表现在脱羧基类型的变化上，还表现在叶片解剖和细胞超微结构上。C4途径是通过非C4祖先中存在的多个基因的共同选择而进化的。C4光合作用基因的共选和适应的趋同在羧化步骤中是明显的。相反，在脱羧基步骤中存在分歧。在65个C4谱系中，约有43个含有使用NADP-苹果酸酶作为主要脱羧酶的物种，而NAD-苹果酸酶(NAD-ME)用于20个谱系，其中16个是优树。除了NAD-ME共选择的可及性可能较低外，C4-NAD-ME是由分离的物种从不同的基因谱系获得的。我们最近的工作表明，NAD-ME共选择C4光合作用途径的机制不同于所有其他C4蛋白，很可能是因为NAD-ME主要作为异源二聚体发挥作用。我们的工作还表明，编码NAD-ME亚基的基因的共选存在可塑性。在桉树中，石竹目和油菜目植物的C4光合作用独立采用NAD-ME。来自不同C4谱系的两个油菜种的C4-NAD-ME基因表现出相似的分子适应性：(A)所有NAD-ME基因α，β1和β2都受到C4进化的影响，(B)β1-NAD-ME基因被选为C4代谢基因。相反，在石竹目的C4物种中，α-NAD-ME(α1)基因的一个额外拷贝可能被用于其在C4途径中的功能。因此，C4-NAD-ME亚型物种的生化趋同可以通过α和β亚基的替代关联来绘制。这些变异是C4功能光合作用途径组分可塑性的另一个例子，支持在C3宿主中安装C4机械的可能性。在本项目中，我们旨在利用互补的生化和结构分析来阐明通过收敛进化选择不同的分子适应是否以及在多大程度上产生了不同eudicot家族的C4-NAD-ME相似的特征。此外，我们的目标是利用A.thaliana NAD-ME突变株将C4-NAD-ME生物工程到BSC线粒体中，以探索代谢结果及其在C3到C4生物工程方法中的可能实现。