Salt tolerant bacteria can be helpful in improving a plant's tolerance to salinity. Although plant-bacteria interactions in response to salt stress have been characterized, the precise molecular mechanisms by which bacterial inoculation alleviates salt stress in plants are still poorly explored. In the present study, we aimed to determine the role of a salt-tolerant plant growth-promoting rhizobacteria (PGPR) Sphingobacterium BHU-AV3 for improving salt tolerance in tomato through investigating the physiological responses of tomato roots and leaves under salinity stress. Tomato plants inoculated with BHU-AV3 and challenged with 200 mM NaCl exhibited less senescence, positively correlated with the maintenance of ion balance, lowered reactive oxygen species (ROS), and increased proline content compared to the non-inoculated plants. BHU-AV3-inoculated plant leaves were less affected by oxidative stress, as evident from a reduction in superoxide contents, cell death, and lipid peroxidation. The reduction in ROS level was associated with the increased antioxidant enzyme activities along with multiple-isoform expression [peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD)] in plant roots. Additionally, BHU-AV3 inoculation induced the expression of proteins involved in (i) energy production [ATP synthase], (ii) carbohydrate metabolism (enolase), (iii) thiamine biosynthesis protein, (iv) translation protein (elongation factor 1 alpha), and the antioxidant defense system (catalase) in tomato roots. These findings have provided insight into the molecular mechanisms of bacteria-mediated alleviation of salt stress in plants. From the study, we can conclude that BHU-AV3 inoculation effectively induces antioxidant systems and energy metabolism in tomato roots, which leads to whole plant protection during salt stress through induced systemic tolerance.

中文翻译：

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鞘氨醇杆菌属 BHU-AV3 通​​过增强抗氧化活性和能量代谢来诱导番茄耐盐性。

耐盐细菌有助于提高植物对盐度的耐受性。尽管响应盐胁迫的植物-细菌相互作用已经得到表征，但细菌接种缓解植物盐胁迫的精确分子机制仍然很少被探索。在本研究中，我们旨在通过研究盐胁迫下番茄根和叶的生理反应，确定耐盐植物根际促生长细菌（PGPR）鞘氨醇杆菌BHU-AV3在提高番茄耐盐性方面的作用。与未接种的植物相比，接种 BHU-AV3 并用 200 mM NaCl 攻击的番茄植物表现出较少的衰老，与离子平衡的维持呈正相关，降低了活性氧 (ROS)，并增加了脯氨酸含量。接种 BHU-AV3 的植物叶子受氧化应激的影响较小，超氧化物含量、细胞死亡和脂质过氧化的减少证明了这一点。ROS水平的降低与植物根部抗氧化酶活性的增加以及多种亚型表达[过氧化物酶（POD）、多酚氧化酶（PPO）和超氧化物歧化酶（SOD）]相关。此外，BHU-AV3 接种诱导参与 (i) 能量产生 [ATP 合酶]、(ii) 碳水化合物代谢（烯醇化酶）、(iii) 硫胺素生物合成蛋白、(iv) 翻译蛋白（延伸因子 1 α）的蛋白质表达，以及番茄根部的抗氧化防御系统（过氧化氢酶）。这些发现为了解细菌介导的缓解植物盐胁迫的分子机制提供了见解。从研究中我们可以得出结论，BHU-AV3 接种有效诱导番茄根部的抗氧化系统和能量代谢，从而通过诱导系统耐受性在盐胁迫期间实现全植物保护。