The Crucial Role of LTTR_0390 in Burkholderia gladioli BBB-01 in Orchestrating Antibiotic Production, Quorum-Sensing Responses, and Pathogenicity on Mushrooms

Burkholderia gladioli strain BBB-01, classified as B. gladioli pv agaricicola, displays broad antagonism against diverse pathogens. We investigated the regulatory role of the LysR-type transcriptional regulator LTTR_0390 and its potential involvement in pathogenicity toward the cultivated button mushroom (Agaricus bisporus). Using insertional mutagenesis, metabolite profiling, transcriptomic analysis, and phenotypic assays, we found that disruption of the lttr_0390 gene extensively reprograms secondary metabolism, for example, upregulating the gladiostatin biosynthetic gene cluster while downregulating the gladiolin cluster. Although this gene disruption did not affect production of quorum-sensing (QS) autoinducers, the mutant exhibited reduced QS-linked behaviors, including motility and biofilm formation. Additionally, disruption of lttr_0390 markedly diminished soft rot symptoms on A. bisporus fruiting bodies. Together, these findings identify LTTR_0390 as a global regulator that coordinates secondary metabolism and QS-linked behaviors while decoupling antifungal activity from mushroom damage.