Comparative transcriptomic responses of tomato to Xanthomonas strains isolated from different hosts

Bacterial spot disease, caused by several Xanthomonas species, poses a significant threat to tomato and pepper production worldwide. Among these pathogens, Xanthomonas vesicatoria and Xanthomonas euvesicatoria pv. euvesicatoria have emerged as particularly important pathogens due to their widespread distribution and economic impact. While both pathogens cause similar symptoms, their genetic and pathogenic differences influence infection dynamics. In this study, we conducted a comparative transcriptomic analysis of tomato plants infected with one strain of X. vesicatoria (isolated from tomato) and one of X. euvesicatoria pv. euvesicatoria (isolated from pepper) to elucidate differential gene expression patterns associated with tomato defense responses. RNA sequencing at 48 hours post-infection revealed a higher number of differentially expressed genes (DEGs) in response to X. vesicatoria, with significant enrichment in pathways related to cell wall modification, secondary metabolism, and phytohormone signaling. On the other hand, infection with X. euvesicatoria pv. euvesicatoria induced a more limited transcriptomic response, with upregulation of a lesser number of genes involved in stress response. Key defense-related genes, including pathogenesis-related proteins (PR1, PR2, PR5), chitinases, and peroxidases, were activated in both infections but showed higher expression levels in response to X. vesicatoria. These findings suggest that X. vesicatoria elicits a stronger immune response in tomato plants than X. euvesicatoria pv. euvesicatoria under the conditions tested. This differential response likely reflects distinct interaction strategies employed by these strains during host colonization. Overall, our study provides new insights into the molecular mechanisms underlying tomato-Xanthomonas interactions and identifies potential molecular targets for developing bacterial spot-resistant cultivars.