Abstract The accumulation of free polyamines (PAs) plays critical role in plants under abiotic stress conditions, while protective traits of bound PAs receiving much less attention, our understanding of the regulation of free PAs converted to bound PAs is limited. In this study, we demonstrated that the PA mediator transglutaminase (TGase) play an important role in improving tomato tolerance to salinity stress, in part because its critical role in inducing accumulation of bound PAs under salt stress. TGase expression was induced upon salt stress. Exogenous phenanthroline (O-phen, a TGase and bound PAs synthesis inhibitor) abolished the TGase-mediated salt tolerance with terminating bound PAs accumulation in TGaseOE plants. O-phen also had a negatively altered on Na+/K+ uptake or homeostasis under salt stress in leaves of TGaseOE plants. Instead, the overexpression of TGase effectively alleviated salt-induced oxidative damage and reduced reactive oxygen species (ROS) over-production, but it was significantly aggravated by O-phen in the TGaseOE plants. Although the ROS generating enzymes (PA oxidase, diamine oxidase and NADPH oxidase) was not affected by application of O-phen, the antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase and monodehydroascorbate reductase) activity was significantly decreased by exogenous O-phen in plants. Furthermore, further analysis showed that the antioxidant enzyme activity positively and closely correlated with the level of bound PAs in TGaseOE plant. Together, these results uncovered a probably function mechanism of TGase-mediated antioxidant enzyme activity to reduced salt-induced oxidative damage, which is partially depended on bound PAs accumulation.

中文翻译：

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TGase通过增强番茄中结合多胺介导的抗氧化酶活性来调节盐胁迫耐受性

摘要 游离多胺（PAs）的积累在非生物胁迫条件下对植物起着至关重要的作用，而结合 PAs 的保护性状受到的关注较少，我们对游离 PAs 转化为结合 PAs 的调控了解有限。在这项研究中，我们证明了 PA 介质转谷氨酰胺酶 (TGase) 在提高番茄对盐胁迫的耐受性方面发挥着重要作用，部分原因是它在诱导盐胁迫下结合 PA 的积累方面发挥了关键作用。TGase 表达在盐胁迫下被诱导。外源性菲咯啉（O-phen，一种 TGase 和结合的 PA 合成抑制剂）消除了 TGase 介导的耐盐性，终止了 TGaseOE 植物中结合 PA 的积累。O-phen 还对 TGaseOE 植物叶片在盐胁迫下的 Na+/K+ 吸收或体内平衡产生负面影响。反而，TGase 的过表达有效减轻了盐诱导的氧化损伤并减少了活性氧 (ROS) 的过量产生，但在 TGaseOE 植物中，O-phen 显着加剧了这种情况。尽管 ROS 生成酶（PA 氧化酶、二胺氧化酶和 NADPH 氧化酶）不受 O-phen 的影响，但外源性 O-phen 显着降低了抗氧化酶（超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶和单脱氢抗坏血酸还原酶）的活性。植物。此外，进一步分析表明，抗氧化酶活性与TGaseOE植物中结合PAs的水平呈正相关且密切相关。总之，这些结果揭示了 TGase 介导的抗氧化酶活性减少盐诱导的氧化损伤的可能功能机制，