Transcriptomic Analyses of Tomato Exhibiting Induced Resistance to Ralstonia solanacearum by Lysobacter enzymogenes JCK1421.

Lysobacter enzymogenes is well known for producing extracellular enzymes and bioactive molecules that suppress a wide range of plant pathogens, including fungi such as Rhizoctonia and Fusarium spp. and oomycetes such as Phytophthora infestans. It also exhibits antagonistic effects against Gram-negative bacteria through the type IV secretion system. Interestingly, L. enzymogenes JCK1421, isolated from the rhizosphere of pine forests, showed neither antifungal nor antibacterial activity, in contrast to other L. enzymogenes strains. However, foliar application of JCK1421 significantly reduced disease symptoms in tomato seedlings challenged with Ralstonia solanacearum. To elucidate the underlying defense mechanisms, comparative transcriptome analysis integrated with network and pathway enrichment approaches was performed. Comparative transcriptome and network analyses identified signaling modules activated by JCK1421 in pathogen-free plants and further enhanced upon R. solanacearum challenge. In challenged plants, JCK1421 treatment strongly induced resistance-related genes, including those encoding Ca2+-dependent proteins and ion channels, hormone biosynthesis components, and mitogen-activated protein kinase cascades-hallmarks of plant immune responses. These findings demonstrate that JCK1421 provides an effective model for investigating microbe-associated defense activation in plants, highlighting its potential as an eco-friendly agent for sustainable crop protection.