Overexpression of oxyR Increases Phenazine-1-Carboxylic Acid Biosynthesis via Small RNA phrS in the Rhizobacterium Strain Pseudomonas PA1201

Phenazine-1-carboxylic acid (PCA) is the primary active component in the newly registered, commercial biopesticide Shenqinmycin and is produced during fermentation by the engineered rhizobacterium strain PA1201. Both and gene clusters contribute to PCA biosynthesis. In this study, we evaluated the role of OxyR in the regulation of PCA biosynthesis in PA1201. We first showed a functional link between expression and PCA biosynthesis. Deletion of and overexpression of both increase PCA biosynthesis. The molecular mechanisms underlying OxyR regulation of PCA production were investigated using several approaches. OxyR acts divergently in and . Overexpression of activated the expression of and -dependent PCA production. However, overexpression of had little effect on -dependent PCA biosynthesis, while deletion of promoted -dependent PCA production and exerted a negative effect on expression. Further, OxyR directly bound to the promoter region. In addition, the regulation of PCA biosynthesis by OxyR was associated with quorum sensing (QS) systems. Overexpression of OxyR positively regulated QS system. Finally, transcriptomic analysis and subsequent genetic analysis revealed the small RNA plays a key role in OxyR-dependent PCA accumulation. Specifically, OxyR directly binds to the promoter region to positively regulate expression wherein PhrS regulates the PCA positive regulator MvfR in order to control PCA biosynthesis.