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.