Data Sheet 5_Halotolerant bacterial endophyte Bacillus velezensis CBE mediates abiotic stress tolerance with minimal transcriptional modifications in Brachypodium distachyon.pdf

Nitrogen and water are the primary resources limiting agricultural production worldwide. We have demonstrated the ability of a novel halotolerant bacterial endophyte, Bacillus velezensis CBE, to induce osmotic stress tolerance in Brachypodium distachyon under nitrogen-deprived conditions. Additionally, we aimed to identify the molecular factors in plants that contribute to the beneficial effects induced by B. velezensis CBE in B. distachyon. To achieve this, we conducted transcriptomic profiling using RNA-seq on 18-day-old B. distachyon seedlings treated with B. velezensis CBE in the presence or absence of available nitrogen, with and without osmotic stress. These profiles were then compared to those obtained from B. distachyon treated with known plant growth-promoting bacterial strains, Azospirillum brasilense Cd and Azoarcus olearius DQS4, under the same growth conditions. We identified differentially expressed genes (DEGs) in response to the combinations of bacterial strains and stress treatments. Interestingly, only 73 transcripts showed significant differential expression in B. velezensis CBE-treated plants under stress conditions, compared to 1,078 DEGs in plants treated with A. brasilense Cd and 2,015 DEGs in A. olearius DQS4. Our findings suggest that the novel endophyte B. velezensis CBE mediates osmotic stress tolerance in B. distachyon through the fine-tuning of molecular mechanisms with minimal transcriptional modifications.

氮与水是全球范围内限制农业生产的核心限制性资源。本研究证实了一株新型耐盐细菌内生菌——贝莱斯芽孢杆菌CBE（Bacillus velezensis CBE），能够在缺氮条件下诱导二穗短柄草（Brachypodium distachyon）产生渗透胁迫耐受性。此外，本研究旨在解析植物体内介导贝莱斯芽孢杆菌CBE对二穗短柄草产生有益效应的分子调控因子。为达成这一研究目标，我们对经贝莱斯芽孢杆菌CBE处理的18日龄二穗短柄草幼苗开展了RNA-seq转录组分析，处理组涵盖有/无有效氮、有/无渗透胁迫的全部组合条件。随后，我们将上述转录组数据与在相同培养条件下，经已知植物促生细菌菌株——巴西固氮螺菌Cd（Azospirillum brasilense Cd）与油养固氮弧菌DQS4（Azoarcus olearius DQS4）处理的二穗短柄草的转录组数据进行了比对分析。本研究鉴定出了响应细菌菌株与胁迫处理组合的差异表达基因（differentially expressed genes, DEGs）。值得注意的是，与经巴西固氮螺菌Cd处理的植株所检测到的1078个DEGs、经油养固氮弧菌DQS4处理的植株所检测到的2015个DEGs相比，经贝莱斯芽孢杆菌CBE处理的胁迫组植株中仅存在73个显著差异表达转录本。本研究结果表明，该新型内生菌贝莱斯芽孢杆菌CBE通过对分子机制进行微调且仅引发极少量转录组修饰，介导了二穗短柄草的渗透胁迫耐受性。