Incidences of heat stress due to the changing global climate can negatively affect the growth and yield of temperature-sensitive crops such as soybean variety, Pungsannamul. Increased temperatures decrease crop productivity by affecting biochemical, physiological, molecular, and morphological factors either individually or in combination with other abiotic stresses. The application of plant growth-promoting endophytic bacteria (PGPEB) offers an ecofriendly approach for improving agriculture crop production and counteracting the negative effects of heat stress. We isolated, screened and identified thermotolerant B. cereus SA1 as a bacterium that could produce biologically active metabolites, such as gibberellin, indole-3-acetic acid, and organic acids. SA1 inoculation improved the biomass, chlorophyll content, and chlorophyll fluorescence of soybean plants under normal and heat stress conditions for 5 and 10 days. Heat stress increased abscisic acid (ABA) and reduced salicylic acid (SA); however, SA1 inoculation markedly reduced ABA and increased SA. Antioxidant analysis results showed that SA1 increased the ascorbic acid peroxidase, superoxide dismutase, and glutathione contents in soybean plants. In addition, heat stress markedly decreased amino acid contents; however, they were increased with SA1 inoculation. Heat stress for 5 days increased heat shock protein (HSP) expression, and a decrease in GmHSP expression was observed after 10 days; however, SA1 inoculation augmented the heat stress response and increased HSP expression. The stress-responsive GmLAX3 and GmAKT2 were overexpressed in SA1-inoculated plants and may be associated with decreased reactive oxygen species generation, altered auxin and ABA stimuli, and enhanced potassium gradients, which are critical in plants under heat stress. The current findings suggest that B. cereus SA1 could be used as a thermotolerant bacterium for the mitigation of heat stress damage in soybean plants and could be commercialized as a biofertilizer only in case found non-pathogenic.

中文翻译：

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植物促生蜡样芽胞杆菌SA1对热胁迫下大豆的耐热作用


全球气候变化导致的热应激事件会对温度敏感作物（如大豆品种 Pungsannamul）的生长和产量产生负面影响。温度升高会单独或与其他非生物胁迫结合影响生化、生理、分子和形态因素，从而降低作物生产力。植物促生长内生细菌（PGPEB）的应用为提高农作物产量和抵消热应激的负面影响提供了一种生态友好的方法。我们分离、筛选和鉴定了耐热蜡状芽孢杆菌SA1，它是一种可以产生生物活性代谢产物（如赤霉素、吲哚-3-乙酸和有机酸）的细菌。 SA1接种提高了大豆植株在正常和热胁迫条件下5天和10天的生物量、叶绿素含量和叶绿素荧光。热应激使脱落酸（ABA）增加，水杨酸（SA）减少；然而，SA1接种显着降低了ABA并增加了SA。抗氧化分析结果表明，SA1增加了大豆植物中抗坏血酸过氧化物酶、超氧化物歧化酶和谷胱甘肽的含量。此外，热应激显着降低氨基酸含量；然而，它们随着SA1接种而增加。热应激5天增加热休克蛋白（HSP）表达，10天后观察到GmHSP表达减少；然而，SA1 接种增强了热应激反应并增加了 HSP 表达。 应激反应性 GmLAX3 和 GmAKT2 在 SA1 接种的植物中过度表达，可能与活性氧生成减少、生长素和 ABA 刺激改变以及钾梯度增强有关，这些对于热应激下的植物至关重要。目前的研究结果表明，蜡状芽胞杆菌SA1可以用作耐热细菌，用于减轻大豆植物的热应激损害，并且只有在发现非致病性的情况下才可以作为生物肥料商业化。