Considering the growth-promoting potential and other regulatory roles of bacteria, we investigated the possible mechanism of the role of Bacillus subtilis in conferring salt tolerance in soybean. Soybean (Glycine max cv. BARI Soybean-5) seeds were inoculated with B. subtilis, either through a presoaking with seeds or a direct application with pot soil. After 20 days of sowing, both the seed- and soil-inoculated plants were exposed to 50, 100, and 150 mM of NaCl for 30 days. A clear sign of oxidative stress was evident through a remarkable increase in lipid peroxidation, hydrogen peroxide, methylglyoxal, and electrolyte leakage in the salt treated plants. Moreover, the efficiency of the ascorbate (AsA)–glutathione (GSH) pathways was declined. Consequently, the plant growth, biomass accumulation, water relations, and content of the photosynthetic pigments were decreased. Salt stress also caused an increased Na⁺/K⁺ ratio and decreased Ca²⁺. On the contrary, the B. subtilis inoculated plants showed increased levels of AsA and GSH, their redox balance, and the activities of the AsA–GSH pathway enzymes, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, and peroxidase. The B. subtilis inoculated plants also enhanced the activities of glyoxalase enzymes, which mitigated methylglyoxal toxicity in coordination with ROS homeostasis. Besides this, the accumulation of K⁺ and Ca²⁺ was increased to maintain the ion homeostasis in the B. subtilis inoculated plants under salinity. Furthermore, the plant water status was uplifted in the salt treated soybean plants with B. subtilis inoculation. This investigation reveals the potential of B. subtilis in mitigating salt-induced oxidative stress in soybean plants through modulating the antioxidant defense and glyoxalase systems along with maintaining ion homeostasis and osmotic adjustments. In addition, it was evident that the soil inoculation performed better than the seed inoculation in mitigating salt-induced oxidative damages in soybean.

中文翻译：

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应用枯草芽孢杆菌研究大豆耐盐诱导氧化应激机制：渗透压调节、离子稳态、抗氧化防御和甲基乙二醛解毒的协同作用

考虑到细菌的生长促进潜力和其他调节作用，我们研究了枯草芽孢杆菌在赋予大豆耐盐性中的作用的可能机制。用枯草芽孢杆菌接种大豆 ( Glycine max cv. BARI Soybean-5) 种子，通过用种子预浸或用盆土直接施用。播种 20 天后，接种种子和土壤的植物均暴露于 50、100 和 150 mM NaCl 中 30 天。通过盐处理植物中脂质过氧化、过氧化氢、甲基乙二醛和电解质泄漏的显着增加，可以明显看出氧化应激的明显迹象。此外，抗坏血酸 (AsA)-谷胱甘肽 (GSH) 途径的效率下降。因此，植物的生长、生物量积累、水分关系和光合色素的含量都降低了。盐胁迫还导致Na ⁺ /K ⁺比率增加和Ca ²⁺减少。相反，枯草芽孢杆菌接种的植物显示出增加的 AsA 和 GSH 水平、它们的氧化还原平衡以及 AsA-GSH 途径酶、超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化物酶、谷胱甘肽S-转移酶和过氧化物酶的活性。接种枯草芽孢杆菌的植物还增强了乙二醛酶的活性，从而减轻了甲基乙二醛的毒性，与 ROS 稳态相协调。除此之外，K ⁺和Ca ²⁺的积累增加以维持在盐度下接种枯草芽孢杆菌的植物中的离子稳态。此外，用枯草芽孢杆菌盐处理的大豆植物中的植物水分状况也得到了提高。接种。这项研究揭示了枯草芽孢杆菌通过调节抗氧化防御和乙二醛酶系统以及维持离子稳态和渗透调节来减轻大豆植物中盐诱导的氧化应激的潜力。此外，很明显，土壤接种在减轻盐分诱导的大豆氧化损伤方面优于种子接种。