Sanya Nanfan Research Institute of Hainan University, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan Province, College of Tropical Crops, Collaborative Innovation Center of Nanfan and High-Efficiency Tropical Agriculture, Hainan University, Hainan province, China; National Key Laboratory for Tropical Crop Breeding, Hainan University, Hainan province, China; Hainan Yazhou Bay Seed Laboratory, Sanya, Hainan province, China.
Sanya Nanfan Research Institute of Hainan University, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan Province, College of Tropical Crops, Collaborative Innovation Center of Nanfan and High-Efficiency Tropical Agriculture, Hainan University, Hainan province, China; National Key Laboratory for Tropical Crop Breeding, Hainan University, Hainan province, China; Hainan Yazhou Bay Seed Laboratory, Sanya, Hainan province, China.
Plant Physiol Biochem. 2023 Aug;201:107814. doi: 10.1016/j.plaphy.2023.107814. Epub 2023 Jun 3.
Malate dehydrogenase (MDH) as an essential metabolic enzyme is widely involved in plant developmental processes. However, the direct relationship between its structural basis and in vivo roles especially in plant immunity remains elusive. In this study, we found that cytoplasmic cassava (Manihot esculenta, Me) MDH1 was essential for plant disease resistance against cassava bacterial blight (CBB). Further investigation revealed that MeMDH1 positively modulated cassava disease resistance, accompanying the regulation of salicylic acid (SA) accumulation and pathogensis-related protein 1 (MePR1) expression. Notably, the metabolic product of MeMDH1 (malate) also improved disease resistance in cassava, and its application rescued the disease susceptibility and decreased immune responses of MeMDH1-silenced plants, indicating that malate was responsible for MeMDH1-mediated disease resistance. Interestingly, MeMDH1 relied on Cys330 residues to form homodimer, which was directly related with MeMDH1 enzyme activity and the corresponding malate biosynthesis. The crucial role of Cys330 residue in MeMDH1 was further confirmed by in vivo functional comparison between overexpression of MeMDH1 and MeMDH1 in cassava disease resistance. Taken together, this study highlights that MeMDH1 confers improved plant disease resistance through protein self-association to promote malate biosynthesis, extending the knowledge of the relationship between its structure and cassava disease resistance.
苹果酸脱氢酶（MDH）作为一种重要的代谢酶，广泛参与植物的发育过程。然而，其结构基础与其在体内作用，特别是在植物免疫中的直接关系仍然难以捉摸。在这项研究中，我们发现细胞质木薯（Manihot esculenta，Me）MDH1 对木薯细菌性条斑病（CBB）的植物抗病性至关重要。进一步的研究表明，MeMDH1 正向调节木薯的抗病性，伴随着水杨酸（SA）积累和病程相关蛋白 1（MePR1）表达的调节。值得注意的是，MeMDH1 的代谢产物（苹果酸）也能提高木薯的抗病性，其应用能挽救 MeMDH1 沉默植物的感病性和降低免疫反应，表明苹果酸是 MeMDH1 介导的抗病性的原因。有趣的是，MeMDH1 依赖 Cys330 残基形成同源二聚体，这与 MeMDH1 酶活性和相应的苹果酸生物合成直接相关。Cys330 残基在 MeMDH1 中的关键作用通过木薯中过表达 MeMDH1 和 MeMDH1 在抗病性方面的体内功能比较进一步得到证实。总之，这项研究强调了 MeMDH1 通过蛋白质自组装赋予植物提高的抗病性，以促进苹果酸的生物合成，扩展了其结构与木薯抗病性之间关系的知识。
