A Volatile Signal Controls Virulence in the Plant Pathogen Pseudomonas syringae pv. syringae and a Strategy for Infection Control in Organic Farming

Abstract

Abstract Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the antimetabolite toxin mangotoxin. The production of this toxin was shown to be regulated by a self-produced signaling molecule. In this study, we determined the structure of the Pss signal molecule belonging to the recently described family of diazeniumdiolate communication molecules. Employing a targeted mass spectrometry-based approach, we provide experimental evidence that the major signal produced by Pss is the volatile compound leudiazen, which controls mangotoxin production and virulence in a detached tomato leaflet infection model. Experimental results demonstrate that KMnO 4 solution inactivates leudiazen and that treatment of infected leaves with KMnO 4 abolishes necrosis. This strategy represents the first example of chemically degrading a signaling molecule to interfere with bacterial communication. The application of KMnO 4 solution, which is regulatorily approved in organic farming, may constitute an environmentally friendly strategy to control Pss infections.