The two-component system RstB/RstA regulates virulence through the Fe3+-siderophore transport operon lpfetABC in the poplar canker bacterium Lonsdalea populi

Abstract Poplar bacterial canker, caused by Lonsdalea populi , seriously threatens the health of poplar plantations. The two-component system is one of the most important signal transduction pathways in bacteria, playing a crucial role in numerical traits including growth, stress tolerance, and pathogenicity; however, their functions in L. populi remain poorly understood. Here, we identified a two-component system (RstB/RstA) in L. populi . The deletion of either rstB or rstA led to a decrease in L. populi virulence, biofilm formation, and tolerance to H 2 O 2 and iron stresses. Based on transcriptomic data of the rstB or rstA mutants, an electrophoretic mobility shift assay confirmed that RstA directly binds to the promoter of lpfetA . Given that lpfetA , lpfetB , and lpfetC are co-transcribed as an operon, these results suggested that RstA likely regulates the lpfetABC operon. The overexpression of either lpfetA , lpfetB , or lpfetC almost abolished bacterial virulence, while resulted in decreased biofilm formation and tolerance to H 2 O 2 . These findings demonstrated that RstA modulates L. populi virulence, at least in part, by regulating the lpfet operon. Overall, our work indicated that RstB/RstA plays an important role in bacterial virulence and stress tolerance.