Data Sheet 3_Assembly and application of a synthetic bacterial community for enhancing barley tolerance to drought.xlsx

Under climate change scenarios for temperate regions in Europe, prolonged droughts pose a major threat to barley production, but few studies have been conducted on stress mitigation strategies using plant-beneficial rhizobacteria. With this in mind, we isolated and screened a culture collection of drought-tolerant bacteria from the barley rhizosphere. From this collection, we assembled a 16-member consortium based on their relative abundances in the rhizosphere after drought and in vitro osmotic stress tolerance (Drought Tolerant Synthetic microbial Community/”DT-SynCom”). Members of the DT-SynCom range from Proteobacteria to Firmicutes and Actinobacteria. We used Oxford Nanopore and Illumina technologies to assemble complete genomes. Whole genome annotation revealed the presence of a number of genes associated with plant growth promoting traits such as IAA biosynthesis, ACC deaminase activity and siderophore production. In vitro assays confirmed auxin production, ACC deaminase activity, siderophore production, inorganic P solubilization, and cellulase and chitinase activities by the selected bacterial strains. The consortium members were not antagonistic to each other, and were either neutral or beneficial to barley shoot and root growth of barley when applied individually in vitro. To clarify the effect of the designed DT-SynCom on barley drought tolerance, a pot experiment was conducted under drought stress conditions. The DT-SynCom reduced the number of wilting leaves and had a positive effect on barley growth under drought. The results of the research suggest that the members of the barley DT-SynCom have beneficial plant growth promoting traits that result in improved plant growth under drought stress.

在欧洲温带地区的气候变化情景下，长期干旱对大麦生产构成重大威胁，但目前针对利用植物有益根际细菌（plant-beneficial rhizobacteria）开展胁迫缓解策略的研究仍较为匮乏。为此，我们从大麦根际分离并筛选得到一批耐旱细菌的培养物保藏库。基于该保藏库中菌株在干旱胁迫后根际的相对丰度以及体外渗透胁迫耐受性，我们构建了一个由16个成员组成的合成菌群（Drought Tolerant Synthetic microbial Community，简称DT-SynCom）。该DT-SynCom的成员涵盖变形菌门（Proteobacteria）、厚壁菌门（Firmicutes）以及放线菌门（Actinobacteria）。我们采用Oxford Nanopore与Illumina测序技术完成了完整基因组的组装。全基因组注释结果显示，该菌群包含多种与植物促生性状相关的基因，例如吲哚乙酸（IAA）生物合成、1-氨基环丙烷-1-羧酸（ACC）脱氨酶活性以及铁载体产生相关的基因。体外实验验证了所筛选菌株具备生长素合成、ACC脱氨酶活性、铁载体产生、无机磷溶解以及纤维素酶与几丁质酶活性。该合成菌群的各菌株之间不存在拮抗作用，且单独体外施用时对大麦的地上部与根系生长均表现为中性或促生效果。为明确所构建的DT-SynCom对大麦耐旱性的影响，我们在干旱胁迫条件下开展了盆栽实验。结果显示，DT-SynCom可减少大麦的萎蔫叶片数量，并在干旱胁迫下对大麦生长产生积极影响。本研究结果表明，大麦DT-SynCom的各菌株均具备有益的植物促生性状，可在干旱胁迫下促进植物生长。