A Malectin-Like Receptor Kinase and Bacterial Motility Shape Tissue-Specific Maize-Xanthomonas vasicola Interactions.

Understanding how pathogens infect different tissue types and how plants mount tissue-specific defences against bacterial pathogens is critical for improving disease resistance. Xanthomonas vasicola pv. vasculorum (Xvv) is a bacterial pathogen of maize that exhibits both vascular and nonvascular lifestyles, offering a unique opportunity to dissect host-pathogen interactions across tissue types. Here, we combined fluorescence microscopy, dual RNA-seq and functional genetics to characterize the interactions between Xvv and maize, both vascular and nonvascular. Using distinct inoculation methods, we reveal temporally and spatially divergent colonization patterns and transcriptional responses in resistant (B73) and susceptible (CML333) maize lines. We show, using transposon insertion lines, that a malectin-like receptor kinase (ZmCrRLK1L19) confers resistance to vascular disease. The gene colocalizes with a major Xvv vascular resistance QTL. Xvv modulates motility and virulence gene expression depending on tissue context; flagellar motility is essential for mesophyll colonization but is dispensable in the xylem. These findings reveal mechanisms underlying tissue-specific resistance and pathogen tissue tropism, providing a foundation for improving broad-spectrum disease resistance in cereal crops.