The Timing of Bacterial Mesophyll Infection Shapes the Leaf Chemical Landscape

Importance: The phyllosphere is a habitat for microorganisms including pathogenic bacteria. Metabolic shifts in the inner leaf spaces for most plant-microbe interactions are unknown, especially for species in understudied plants like barley (). pv. translucens (Xtt) and pv. undulosa (Xtu) are phylogenomically distinct, but both colonize barley leaves for pathogenesis. In this study, we used untargeted metabolomics to shed light on Xtu and Xtt metabolic signatures. Our findings revealed a dynamic metabolic landscape that changes over time, rather than exhibiting a pattern associated with individual pathovars. These results provide initial insights into the metabolic mechanisms of inner leaf pathogenesis.