This research identifies a unique nutritional strategy used by bacteria of the genus Xanthomonas to infect more than 400 plant species. The authors show that the effector AvrBs2 functions as a synthase, converting host-derived galactose into a compound called xanthosan. This molecule is then released into the plant’s extracellular space, where the bacterium retrieves it via the XanT transporter and breaks it down using the enzyme XanP as a nutrient source.
This discovery enabled the development of an “anti-nutritional” disease control strategy by engineering transgenic plants that express XanP. These plants degrade xanthosan before the bacteria can use it, thereby enhancing disease resistance without compromising plant growth.