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

<i>Lysobacter enzymogenes</i> is well known for producing extracellular enzymes and bioactive molecules that suppress a wide range of plant pathogens, including fungi such as <i>Rhizoctonia</i> and <i>Fusarium</i> spp. and oomycetes such as <i>Phytophthora infestans</i>. It also exhibits antagonistic effects against Gram-negative bacteria through the type IV secretion system. Interestingly, <i>L. enzymogenes</i> JCK1421, isolated from the rhizosphere of pine forests, showed neither antifungal nor antibacterial activity, in contrast to other <i>L. enzymogenes</i> strains. However, foliar application of JCK1421 significantly reduced disease symptoms in tomato seedlings challenged with <i>Ralstonia solanacearum</i>. 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 <i>R. solanacearum</i> 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.