Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin, People's Republic of China.
Key Laboratory of Agricultural Microbiology of Heilongjiang Province, College of Life Sciences, Northeast Agricultural University, Harbin, People's Republic of China.
Physiol Plant. 2024 Jul-Aug;176(4):e14411. doi: 10.1111/ppl.14411.
Plant growth-promoting rhizobacteria (PGPR) are known for their role in ameliorating plant stress, including alkaline stress, yet the mechanisms involved are not fully understood. This study investigates the impact of various inoculum doses of Bacillus licheniformis Jrh14-10 on Arabidopsis growth under alkaline stress and explores the underlying mechanisms of tolerance enhancement. We found that all tested doses improved the growth of NaHCO-treated seedlings, with 10 cfu/mL being the most effective. Transcriptome analysis indicated downregulation of ethylene-related genes and an upregulation of polyamine biosynthesis genes following Jrh14-10 treatment under alkaline conditions. Further qRT-PCR analysis confirmed the suppression of ethylene biosynthesis and signaling genes, alongside the activation of polyamine biosynthesis genes in NaHCO-stressed seedlings treated with Jrh14-10. Genetic analysis showed that ethylene signaling-deficient mutants (etr1-3 and ein3-1) exhibited greater tolerance to NaHCO than the wild type, and the growth-promoting effect of Jrh14-10 was significantly diminished in these mutants. Additionally, Jrh14-10 was found unable to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, indicating it does not reduce the ethylene precursor ACC in Arabidopsis. However, Jrh14-10 treatment increased the levels of polyamines (putrescine, spermidine, and spermine) in stressed seedlings, with spermidine particularly effective in reducing HO levels and enhancing F/F under NaHCO stress. These findings reveal a novel mechanism of PGPR-induced alkaline tolerance, highlighting the crosstalk between ethylene and polyamine pathways, and suggest a strategic redirection of S-adenosylmethionine towards polyamine biosynthesis to combat alkaline stress.
植物促生根际细菌（PGPR）以其缓解植物胁迫的作用而闻名，包括碱性胁迫，但涉及的机制尚未完全了解。本研究调查了不同剂量的地衣芽孢杆菌 Jrh14-10 对拟南芥在碱性胁迫下生长的影响，并探讨了增强耐受性的潜在机制。我们发现所有测试剂量都改善了碳酸氢钠处理幼苗的生长，其中 10cfu/mL 效果最显著。转录组分析表明，在碱性条件下，Jrh14-10 处理后乙烯相关基因下调，多胺生物合成基因上调。进一步的 qRT-PCR 分析证实，Jrh14-10 处理的碳酸氢钠胁迫幼苗中乙烯生物合成和信号基因受到抑制，同时多胺生物合成基因被激活。遗传分析表明，乙烯信号缺陷突变体（etr1-3 和 ein3-1）比野生型对碳酸氢钠的耐受性更强，而 Jrh14-10 在这些突变体中的促生长作用明显减弱。此外，发现 Jrh14-10 不能产生 1-氨基环丙烷-1-羧酸（ACC）脱氨酶，表明它不能在拟南芥中降低乙烯前体 ACC。然而，Jrh14-10 处理增加了胁迫幼苗中多胺（腐胺、亚精胺和精胺）的水平，其中亚精胺在降低 HO 水平和增强 NaHCO 胁迫下的 F/F 方面特别有效。这些发现揭示了 PGPR 诱导碱性耐受性的新机制，强调了乙烯和多胺途径之间的串扰，并提出了一种将 S-腺苷甲硫氨酸战略性地重新定向到多胺生物合成以应对碱性胁迫的策略。
