Streptomyces alleviate abiotic stress in plant by producing pteridic acids

Abstract 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 a class of Streptomyces effectively alleviates the drought and salinity stress by producing new spiroketal polyketide pteridic acid H (1) and its isomer F (2). The bifunctional pteridic acid (pta) biosynthetic gene cluster (BGC), which is also responsible for the biosynthesis of the known antimicrobial elaiophylin, was confirmed by bioinformatic analysis and in vivo CRISPR base editing. Pteridic acids H and F exhibited profound effects in promoting root growth in Arabidopsis at a concentration of 0.5 ng mL-1 (1.3 nM) under abiotic stress, indicating they are a new class of plant stress regulators. Phylogenetic and geographical distribution analysis revealed that the pta BGC was mainly disseminated by vertical transmission and occasional horizontal gene transfer and is widely distributed in numerous Streptomyces in different environments. This discovery reveals a new perspective for understanding plant-Streptomyces interactions and provides a novel, promising approach for utilising beneficial Streptomyces and their secondary metabolites in agriculture to mitigate the detrimental effects of climate change.