Coordination and Regulation of Xanthomonas Lifestyle by Sensing Environmental and Host Signals.

Plant pathogenic bacteria causes great damage to global agriculture by infecting economically important crops and reducing yield. Among them, Xanthomonas spp. are 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, Xanthomonas 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 (MCPs), 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. Xanthomonas 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 Xanthomonas 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 Xanthomonas-induced plant diseases and improve crop protection.