Coordination and Regulation of <i>Xanthomonas</i> Lifestyle by Sensing Environmental and Host Signals

Plant-pathogenic bacteria cause great damage to global agriculture by infecting economically important crops and reducing yield. Among them, <i>Xanthomonas</i> spp. are a particularly important group of plant pathogens, as they have the ability to colonize hundreds of plant species. These pathogens exhibit a dual lifestyle, existing both epiphytically on plant surfaces and endophytically within host tissues. To establish infection, <i>Xanthomonas</i> must adapt to a range of abiotic and biotic stresses, including temperature, light, osmotic changes, oxidative stress, and host immune responses. The bacteria rely on sophisticated environmental sensing mechanisms, including chemotaxis mediated by methyl-accepting chemotaxis proteins, which help them detect host-derived chemical signals and navigate toward infection sites. Limited availability of nutrients, such as iron and magnesium within host tissues, acts as a cue that further modulates bacterial physiology and virulence. <i>Xanthomonas</i> has evolved efficient strategies to scavenge and store these nutrients, integrating these signals through tightly regulated gene networks. A central regulatory system involves diffusible signal factor (DSF)-mediated quorum sensing, which coordinates community-level behaviors such as motility, extracellular polysaccharide production, and secretion of virulence effectors. This review discusses recent advances in understanding how <i>Xanthomonas</i> integrates environmental and host-derived signals to regulate its pathogenicity. It emphasizes the role of DSF signaling, chemotaxis, and micronutrient acquisition in disease progression and host-pathogen interactions. Insights into these adaptive and regulatory mechanisms offer promising avenues for developing targeted strategies to control <i>Xanthomonas</i>-induced plant diseases and improve crop protection. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.