Plant growth-promoting rhizobacteria (PGPR) have been widely reported to enhance plant drought tolerance through multiple direct and indirect mechanisms. However, the role of branched-chain amino acids (BCAAs) in PGPR-induced drought resistance in crops remains largely unclear. In this study, we investigated the PGPR strain Paraburkholderia sp. GD17 and elucidated its regulatory mechanisms in alleviating drought stress in cucumber. Inoculation with GD17 significantly improved plant growth and water retention capacity under drought conditions. Transcriptomic analysis revealed that GD17 activated the abscisic acid (ABA) signaling pathway and promoted the degradation of BCAAs that had accumulated under drought stress. Further physiological and molecular evidence suggested that both ABA signaling and BCAA catabolism maybe jointly contributed to the upregulation of reactive oxygen species (ROS)-scavenging enzyme activities, thereby alleviating oxidative damage. Collectively, these findings provide new insights into how PGPR enhances plant drought tolerance through ABA-mediated regulation of BCAA metabolism. • For the first time, it was revealed that PGPR-GD17 participates in the metabolic activities of branched-chain amino acids by specifically inducing the abscisic acid signaling pathway. • The study comprehensively utilized physiological phenotypes, dynamic monitoring of relative water content, transcriptomes, etc. data, and conducted reverse genetic verification using abscisic acid synthesis inhibitors to clarify that the abscisic acid signal specifically induces branched-chain amino acid metabolism.
Zhang et al. (Wed,) studied this question.