Putrescine Is an Intraspecies and Interkingdom Cell-Cell Communication Signal Modulating the Virulence of .

The infections caused by become a severe problem in recent years, but the regulatory mechanisms that govern the bacterial virulence remain to be fragmental. Here we report the investigation of potential involvement of polyamines in regulation of virulence. We showed that null mutation of encoding arginine decarboxylase dramatically decreased the bacterial swimming motility, swarming motility and biofilm formation, and exogenous addition of putrescine effectively rescues the defective phenotypes of . HPLC and mass spectrometry analysis validated that was essential for production of putrescine in . In addition, we demonstrated that EC1 could detect and response to putrescine molecules produced by itself or from host plant through specific transporters. Among the two transporters identified, the one represented by PotF played a dominated role over the other represented by PlaP in modulation of putrescine-dependent biological functions. Furthermore, we provided evidence that putrescine signal is critical for EC1 bacterial invasion and virulence against rice seeds. Our data depict a novel function of putrescine signal in pathogen-host communication and in modulation of the virulence of an important plant bacterial pathogen.