BysR, a LysR-type Pleiotropic Regulator, Controls Production of Occidiofungin by Activating the LuxR-type transcriptional regulator AmbR1 in Burkholderia sp. JP2-270

Abstract

Occidiofungin is a highly effective antifungal glycopeptide produced by certain Burkholderia strains. The ocf gene cluster directing occidiofungin biosynthesis is regulated by cluster-specific regulators encoded by ambR homolog(s) within the same gene cluster, while it remains unknown to what extent occidiofungin biosynthesis is connected with the core regulation network. Here, we report that a LysR-type regulator BysR acts as a pleotropical regulator, and is essential for occidiofungin biosynthesis by directly activating ambR1 transcription in Burkholderia sp. JP2-270. Deletion of bysR and ocfE both abolished the antifungal activity in JP2-270. This defect of the bysR mutant can be recovered by constitutively expressing bysR or ambR1 but not by ambR2. The EMSA assay collectively showed that BysR regulates ambR1 through direct binding to its promoter region. Taken together, occidiofungin produced by JP2-270 is the main substance inhibiting M. oryzae, and BysR controls occidiofungin production by directly activating the expression of ambR1. Besides, transcriptomic analysis revealed altered expression of 350 genes in response to bysR deletion, and the genes engaged in flagellar assembly and bacterial chemotaxis are the most enriched pathways. Also, 400 putative loci targeted by BysR were identified by DAP-seq in JP2-270. These loci not only include genes engaged in key metabolic pathways but also genes involved in secondary metabolic pathways. Collectively, we proposes that BysR may be a novel pleiotropic regulator, and ambR1 is an important target gene of BysR, which is an intra-cluster transcriptional regulatory gene that further activates the transcription of ocf gene cluster.