Autoinducer-2 Mediated Quorum Sensing Stabilizes Cooperation between Pantoea alhagi and Synthetic Bacterial Communities, Synergistically Improving Drought Tolerance in Wheat

Quorum sensing (QS), a mechanism of intercellular communication, plays a crucial role in regulating the microbial community behavior and function. However, the role of the LuxS/AI-2 system in shaping wheat rhizosphere microbiota remains unclear. In this study, the luxS gene, encoding autoinducer-2 (AI-2) synthase, was deleted from Pantoea alhagi LTYR-11Z, resulting in significantly impaired biofilm formation, AI-2 production, and root colonization. A 4-week pot experiment revealed that the wild-type (WT) strain markedly altered the composition, diversity, and structure of rhizosphere bacterial communities compared to the control and ΔluxS mutant groups. Notably, AI-2-mediated microbial recruitment enhanced hybrid biofilm formation. Potting drought experiments showed that AI-2 signaling induced SynCom collaboration, allowing WT+SynCom to activate antioxidant enzymes more efficiently and increase the total N/P concentration in wheat, alleviating drought stress damage. These findings demonstrate that QS acts as a selective force in the rhizosphere microbiome assembly, enriching plant-beneficial species and improving stress resilience.