Table_4_Bacillus halotolerans KKD1 induces physiological, metabolic and molecular reprogramming in wheat under saline condition.DOCX

Salt stress decreases plant growth and is a major threat to crop yields worldwide. The present study aimed to alleviate salt stress in plants by inoculation with halophilic plant growth-promoting rhizobacteria (PGPR) isolated from an extreme environment in the Qinghai–Tibetan Plateau. Wheat plants inoculated with Bacillus halotolerans KKD1 showed increased seedling morphological parameters and physiological indexes. The expression of wheat genes directly involved in plant growth was upregulated in the presence of KKD1, as shown by real-time quantitative PCR (RT-qPCR) analysis. The metabolism of phytohormones, such as 6-benzylaminopurine and gibberellic acid were also enhanced. Mining of the KKD1 genome corroborated its potential plant growth promotion (PGP) and biocontrol properties. Moreover, KKD1 was able to support plant growth under salt stress by inducing a stress response in wheat by modulating phytohormone levels, regulating lipid peroxidation, accumulating betaine, and excluding Na+. In addition, KKD1 positively affected the soil nitrogen content, soil phosphorus content and soil pH. Our findings indicated that KKD1 is a promising candidate for encouraging wheat plant growth under saline conditions.

盐胁迫会抑制植物生长，是全球范围内威胁作物产量的主要逆境因素。本研究旨在通过接种分离自青藏高原极端环境的嗜盐植物促生根际细菌（halophilic plant growth-promoting rhizobacteria, PGPR），缓解植物面临的盐胁迫。接种耐盐芽孢杆菌KKD1的小麦幼苗，其形态参数与生理指标均显著提升。实时定量聚合酶链式反应（real-time quantitative PCR, RT-qPCR）分析结果显示，接种KKD1后，小麦体内直接参与植物生长过程的基因表达量显著上调。6-苄氨基腺嘌呤、赤霉素等植物激素的代谢过程亦得到增强。对KKD1基因组的挖掘分析证实了其具备潜在的植物生长促生（plant growth promotion, PGP）与生物防治特性。此外，KKD1可通过调控小麦体内植物激素水平、调节脂质过氧化过程、积累甜菜碱以及排出钠离子，诱导小麦产生胁迫应答反应，从而在盐胁迫环境下促进植物生长。同时，KKD1还可显著改善土壤氮含量、磷含量与土壤pH值。本研究结果表明，KKD1是极具应用潜力的候选菌株，可用于促进盐渍环境下小麦的生长发育。