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.