State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Agriculture, South China Agriculture University, Guangzhou 510642, China.
School of Life Sciences, Tsinghua University, Beijing 100084, China.
Int J Mol Sci. 2022 Sep 2;23(17):10028. doi: 10.3390/ijms231710028.
Malate dehydrogenase, which facilitates the reversible conversion of malate to oxaloacetate, is essential for energy balance, plant growth, and cold and salt tolerance. However, the genome-wide study of the MDH family has not yet been carried out in tomato (Solanum lycopersicum L.). In this study, 12 MDH genes were identified from the S. lycopersicum genome and renamed according to their chromosomal location. The tomato MDH genes were split into five groups based on phylogenetic analysis and the genes that clustered together showed similar lengths, and structures, and conserved motifs in the encoded proteins. From the 12 tomato MDH genes on the chromosomes, three pairs of segmental duplication events involving four genes were found. Each pair of genes had a Ka/Ks ratio < 1, indicating that the MDH gene family of tomato was purified during evolution. Gene expression analysis exhibited that tomato MDHs were differentially expressed in different tissues, at various stages of fruit development, and differentially regulated in response to abiotic stresses. Molecular docking of four highly expressed MDHs revealed their substrate and co-factor specificity in the reversible conversion process of malate to oxaloacetate. Further, co-localization of tomato MDH genes with quantitative trait loci (QTL) of salt stress-related phenotypes revealed their broader functions in salt stress tolerance. This study lays the foundation for functional analysis of MDH genes and genetic improvement in tomato.
苹果酸脱氢酶（Malate dehydrogenase，MDH）能够促进苹果酸向草酰乙酸的可逆转化，对于维持能量平衡、植物生长以及耐冷和耐盐性至关重要。然而，在番茄（Solanum lycopersicum L.）中，尚未对 MDH 家族进行全基因组研究。在本研究中，从番茄基因组中鉴定出 12 个 MDH 基因，并根据其染色体位置重新命名。基于系统发育分析，将番茄 MDH 基因分为 5 组，聚类在一起的基因在编码蛋白中具有相似的长度、结构和保守基序。在染色体上的 12 个番茄 MDH 基因中，发现了涉及 4 个基因的三对片段重复事件。每对基因的 Ka/Ks 比值<1，表明番茄 MDH 基因家族在进化过程中受到了纯化。基因表达分析表明，番茄 MDH 在不同组织、果实发育的不同阶段以及对非生物胁迫的不同调节中存在差异表达。对 4 个高表达 MDH 的分子对接表明，它们在苹果酸向草酰乙酸的可逆转化过程中具有底物和辅酶特异性。此外，番茄 MDH 基因与与盐胁迫相关表型的数量性状位点（Quantitative trait loci，QTL）的共定位揭示了它们在耐盐性方面的更广泛功能。本研究为番茄 MDH 基因的功能分析和遗传改良奠定了基础。
