BysR, a LysR-Type Pleiotropic Regulator, Controls Production of Occidiofungin by Activating the LuxR-Type Transcriptional Regulator AmbR1 in sp. Strain JP2-270.

Occidiofungin is a highly effective antifungal glycopeptide produced by certain strains. The gene cluster, responsible for occidiofungin biosynthesis, is regulated by the cluster-specific regulators encoded by an homolog(s) within the same gene cluster, while the extent to which occidiofungin biosynthesis is connected with the core regulation network remains unknown. Here, we report that the LysR-type regulator BysR acts as a pleiotropic regulator and is essential for occidiofungin biosynthesis. Magnaporthe oryzae was used as an antifungal target in this study, and deletion of and abolished the antagonistic activity against M. oryzae in sp. strain JP2-270. The Δ defect can be recovered by constitutively expressing or , but not . Electrophoretic mobility shift assays (EMSAs) collectively showed that BysR regulates by directly binding to its promoter region. In addition, transcriptomic analysis revealed altered expression of 350 genes in response to deletion, and the genes engaged in flagellar assembly and bacterial chemotaxis constitute the most enriched pathways. Also, 400 putative BysR-targeted loci were identified by DNA affinity purification sequencing (DAP-seq) in JP2-270. These loci include not only genes engaged in key metabolic pathways but also those involved in secondary metabolic pathways. To conclude, the occidiofungin produced by JP2-270 is the main substance inhibiting M. oryzae, and BysR controls occidiofungin production by directly targeting , an intracluster transcriptional regulatory gene that further activates the transcription of the gene cluster. We report for the first time that occidiofungin production is regulated by the global transcriptional factor BysR, by directly targeting the specific regulator , which further promotes the transcription of genes. BysR also acts as a pleiotropic regulator that controls various cellular processes in sp. strain JP2-270. This study provides insight into the regulatory mechanism of occidiofungin synthesis and enhances our understanding of the regulatory patterns of the LysR-type regulator.