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The phytohormone indole-3-acetic acid induces quorum sensing signal DSF turnover via a positive feedback biosynthetic loop in the phytopathogen Xanthomonas campestris
Author(s)
Li, Si Nan
Zhang, Ming Lei
Cui, Ying
Li, Lin
Jiang, Lian
Tian, Dong Lan
Gu, Yu Cheng
He, Ya Wen
Zhou, Lian
Song, Kai
Date Issued
December 1, 2026
Type
Article
Abstract
Indole-3-acetic acid (IAA) accumulates in host plants following infection by Xanthomonas campestris pv. campestris (Xcc), the causal agent of cruciferous black rot. How exposure to IAA affects the invading Xcc remains unclear. Here, we demonstrate that either exogenous addition of IAA or endogenous production of IAA induced turnover of the quorum sensing (QS) signal diffusible signaling factor (DSF) in a RpfB-dependent manner. IAA addition prevented the cytoplasmic and culture pH decline. Transcriptomic analyses revealed four IAA-regulated gene clusters. Specifically, IAA induced the expression of trpB-A, enhancing tryptophan biosynthesis and intracellular IAA accumulation, and thereby establishing a self-reinforcing synthesis loop. IAA upregulated F0F1 ATP synthases and a resistance-nodulation-cell division (RND)-family efflux pump HepABCD to induce a pH-dependent DSF turnover. Moreover, IAA downregulated another RND family efflux pump IaepABCDE to induce a pH-independent DSF turnover. Finally, the IAA-regulated gene clusters were transcribed during the XC1 infection of cabbage. Collectively, these findings reveal a previously unrecognized role of IAA in modulating bacterial QS, underscoring the importance of IAA in the molecular dialogue between the pathogen and its host.
Citation
Stress Biology, 6(1), 2026