Streptomyces alleviate abiotic stress in plant by producing pteridic acids

Soil microbiota can confer fitness advantages to plants and increase crop resilience to drought and other abiotic stressors. However, there is little evidence on the mechanisms correlating a microbial trait with plant abiotic stress tolerance. Here, we report that Streptomyces effectively alleviate drought and salinity stress by producing spiroketal polyketide pteridic acid H (1) and its isomer F (2), both of which promote root growth in Arabidopsis at a concentration of 1.3 nM under abiotic stress. Transcriptomics profile showed increased expression of multiple stress responsive genes in Arabidopsis seedlings after pteridic acids treatment. The bifunctional biosynthetic gene cluster of pteridic acids and antimicrobial elaiophylin is confirmed in vivo and mainly disseminated by vertical transmission which is geographically distributed in various environments. This discovery reveals a perspective for understanding plant-Streptomyces interactions and provides a promising approach for utilising beneficial Streptomyces and their secondary metabolites in agriculture to mitigate the detrimental effects of climate change.

土壤微生物群（Soil microbiota）可赋予植物生存适配优势，并提升作物对干旱及其他非生物胁迫（abiotic stressors）的抗逆性。然而，目前鲜有研究阐明微生物性状与植物非生物胁迫耐受性之间的关联机制。本研究发现，链霉菌（Streptomyces）可通过产生螺环聚酮类化合物（spiroketal polyketide）蝶啶酸H（pteridic acid H，1）及其异构体F（2），有效缓解干旱与盐胁迫；在非生物胁迫条件下，这两种化合物在1.3 nM的浓度下即可促进拟南芥（Arabidopsis）的根系生长。转录组谱（transcriptomics profile）分析显示，经蝶啶酸类化合物处理后，拟南芥幼苗体内多个胁迫响应基因的表达量显著上调。本研究在体内验证了蝶啶酸与抗菌化合物埃莱菲林（elaiophylin）的双功能生物合成基因簇（bifunctional biosynthetic gene cluster），该基因簇主要通过垂直传递（vertical transmission）方式进行扩散，且在全球多种不同环境中均有分布。本研究不仅揭示了理解植物-链霉菌互作关系的全新视角，更为农业生产中利用有益链霉菌及其次生代谢产物以缓解气候变化带来的不利影响提供了极具前景的可行途径。