In plants, reactive oxygen species accumulate to a toxic level under various abiotic stresses. Many antioxidant defense systems require NADPH as a principal reducing energy equivalent. However, the source of NADPH and the molecular mechanisms associated with the maintenance of cytoplasmic redox balance are still unknown. The present study describes Vigna NADH kinase (VlNADHK), an enzyme involved in NADPH synthesis and prefers NADH as a diphospho-nicotinamide nucleotide donor. We analyzed the enzymatic activity of a putative cytoplasmic NADH kinase during waterlogging in contrasting mung bean genotypes Vigna luteola (tolerant) and Vigna radiata cv. T44 (susceptible) under pot-culture condition. The tolerant cultivar showed higher enzymatic activity under waterlogging as well as after recovery. Similarly, the transcript level of waterlogging-induced NADHK expression was also studied and found to be upregulated in response to waterlogging in the roots of V. luteola and T44. PCR amplicons of partial and full-length sequences were cloned and sequenced from V. luteola. To the best of our knowledge, this is the first time an ATP-dependent NADH kinase gene has been recognized as a component of waterlogging stress tolerance in legumes. Our study indicated that this cytoplasmic NADH kinase is a primary source of the cytosolic NADPH and might have a role in waterlogging tolerance in legumes.

中文翻译：

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耐胁迫野生绿豆（Vigna luteola (Jacq.) Benth.）NADH Kinase-3 的鉴定和表征，可能在耐涝中发挥作用

在植物中，活性氧在各种非生物胁迫下积累到毒性水平。许多抗氧化防御系统需要 NADPH 作为主要的还原能量当量。然而，NADPH 的来源和与维持细胞质氧化还原平衡相关的分子机制仍然未知。本研究描述了豇豆 NADH 激酶 (VlNADHK)，这是一种参与 NADPH 合成的酶，更喜欢 NADH 作为二磷酸烟酰胺核苷酸供体。我们在对比绿豆基因型 Vigna luteola（耐受）和 Vigna radiata cv 中分析了在涝渍期间推定的细胞质 NADH 激酶的酶活性。T44（敏感）在盆栽条件下。耐涝品种在涝渍和恢复后均表现出较高的酶活性。相似地，还研究了涝渍诱导的 NADHK 表达的转录水平，发现在 V. luteola 和 T44 的根部因涝渍而上调。从 V.luteola 中克隆和测序了部分和全长序列的 PCR 扩增子。据我们所知，这是首次将 ATP 依赖性 NADH 激酶基因确认为豆类耐涝胁迫的一个组成部分。我们的研究表明，这种细胞质 NADH 激酶是细胞质 NADPH 的主要来源，可能在豆类耐涝中起作用。这是首次将 ATP 依赖性 NADH 激酶基因确认为豆类耐涝胁迫的一个组成部分。我们的研究表明，这种细胞质 NADH 激酶是细胞质 NADPH 的主要来源，可能在豆类耐涝中起作用。这是首次将 ATP 依赖性 NADH 激酶基因确认为豆类耐涝胁迫的一个组成部分。我们的研究表明，这种细胞质 NADH 激酶是细胞质 NADPH 的主要来源，可能在豆类耐涝中起作用。