Abstract:[Background] Pseudomonas protegens H78, a biocontrol strain isolated from the rape rhizosphere, can produce multiple broad-spectrum antibiotics such as pyoluteorin (Plt). Plt biosynthesis is completely inhibited by the rsmA/E dual mutation in Pseudomonas protegens H78. [Objective] The aim of this study is to screen the downstream regulatory factors for reactivating Plt biosynthesis in the H78ΔrsmA/E dual mutant by transposon mutagenesis. [Methods] the red fluorescent protein (RFP) gene was inserted downstream of the Plt biosynthetic gene pltL by homologous recombination to indicate the activation of Plt operon expression. the target gene was screened and located by the transposon-based random insertion mutation and the semi-random PCR. the gene function was further confirmed by the gene complement method. [Results] A mutant with high yield of Plt was screened from about 20 000 transposon insertion mutants of H78ΔrsmA/E, and its mutation site was determined to be within the hmgA gene. In turn, the hmgA complementation can inhibit Plt biosynthesis in the H78ΔrsmA/E strain. [Conclusion] In the H78ΔrsmA/E dual mutant of P. protegens, the hmgA gene shows strong inhibitory effect on Plt biosynthesis. The hmgA gene is a potential downstream regulatory gene of RsmA/E. This study lays a foundation for further elucidating the regulatory mechanism and network of Plt biosynthesis and improving the yield of Plt through genetic engineering.
