Decoding the dual function of NAD-malic enzyme: from a universal role in malate respiration to a specific function in C4 photosynthesis

解读 NAD-苹果酸酶的双重功能：从苹果酸呼吸中的普遍作用到 C4 光合作用中的特定功能

• 批准号: 392217267
• 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
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/392217267?language=en
• 关键词: Decoding; dual; function; NAD; malic

In the C3 plant A. thaliana, malate levels produced during photosynthesis increase during the day and accumulate in the vacuole until metabolic demands are sensed. During the night, malate is utilized in the mitochondria to furnish part of the TCA cycle and to replenish the pool of TCA cycle intermediates. This function is fulfilled through the concerted action of NAD-dependent malic enzyme (NAD-ME) and malate dehydrogenase. Apart from its role in malate respiration, NAD-ME was co-opted to provide CO2 for the Calvin cycle in the bundle sheath cells during the photosynthetic metabolism in some C4 plants. The NAD-ME catalyzes the oxidative decarboxylation of malate, producing pyruvate, CO2, and NADH and is localized exclusively in mitochondria. Until now, there are no reports on the existence of a specific NAD-ME isoform only involved in C4 metabolism. This poses the question if NAD-ME performs a dual function in C4 plants or if a C4 specific isoform exist. Gene duplication would be a pre-condition for the evolution of the C4 metabolism as it allows the plant to retain an original gene while a duplicate version can acquire advantageous alterations. Interestingly, the C3 T. hassleriana and C4 G. gynandra Cleome species underwent a whole genome duplication that occurred aPproximately 13.7 mya. More precisely, a gene duplication of one NAD-ME beta-subunit is found in both Cleome species. We thus hypothesize that the duplication of the NAD-ME b-subunit was a potentiating evolutionary event that aided the repeated evolution of the NAD-ME subtype C4 photosynthesis in this genus. During this project, we will analyse the evolutionary transition of NAD-ME from a TCA cycle-associated enzyme to a C4 decarboxylase in bundle sheath cells using as model organisms the genus Cleome. Our main objective is to describe the mechanisms behind the recruitment of NAD-ME into the C4 pathway. To answer these questions, we propose a work program that combines protein biochemistry methods (proteomics, enzymology, structural analyses) with an in vivo loss-of-function complementation approach and immunohistochemical, transcriptomics, and phylogenetic analyses.

在C3植物A. thaliana中，白天光合作用期间产生的苹果酸水平会增加，并积聚在液泡中，直到感觉到代谢需求。在夜间，在线粒体中使用苹果酸盐可提供TCA周期的一部分，并补充TCA循环中间体的池。通过NAD依赖性苹果酶（NAD-ME）和苹果酸脱氢酶的一致作用来实现此功能。除了其在苹果酸呼吸中的作用外，NAD-ME还选择在某些C4植物的光合代谢期间为束鞘细胞中的Calvin循环提供二氧化碳。 NAD-ME催化苹果酸，产生丙酮酸，二氧化碳和NADH的氧化脱羧，并仅在线粒体中定位。到目前为止，还没有关于仅参与C4代谢的特定NAD-ME同工型的报告。这提出了一个问题，即NAD-ME是否在C4植物中执行双重功能，或者是否存在C4特异性同工型。基因复制将是C4代谢进化的前提条件，因为它允许植物保留原始基因，而重复版本可以获得有利的改变。有趣的是，C3 T. Hassleriana和C4 G. Gynandra Cleome物种经历了大约13.7 Mya的整个基因组重复。更确切地说，在两种克利姆物种中都发现了一个NAD-ME Beta-Subunit的基因重复。因此，我们假设NAD-ME B-Subunit的重复是一个增强的进化事件，该事件有助于该属中NAD-ME亚型C4光合作用的重复演化。在此项目中，我们将使用AS Model Symismers Scleome属分析NAD-ME从TCA周期相关酶向C4脱羧酶中的C4脱羧酶的进化过渡。我们的主要目标是描述NAD-ME招募到C4途径的机制。为了回答这些问题，我们提出了一项工作计划，将蛋白质生物化学方法（蛋白质组学，酶学，结构分析）与体内功能丧失互补方法和免疫组织化学，转录组学和系统发育分析相结合。

项目成果

Respiratory and C4-photosynthetic NAD-malic enzyme coexist in bundle sheath cells mitochondria and evolved via association of differentially adapted subunits

呼吸酶和 C4 光合 NAD-苹果酸酶共存于束鞘细胞线粒体中，并通过差异适应亚基的关联而进​​化

• DOI: 10.1101/2021.06.16.448762
• 发表时间: 2021
• 期刊: bioRxiv
• 作者: Hüdig M;Tronconi MA;Zubimendi JP;Sage TL;Poschmann G;Bickel D;Gohlke H;Maurino VG
• 通讯作者: Maurino VG