ClpP mediates antagonistic interaction of Lysobacter enzymogenes with a crop fungal pathogen

Abstract ClpXP protease is widely distributed in the bacterial kingdom and plays a vital role in maintaining protein quality, physiology, metabolism, and virulence in pathogenic bacteria; however, its functionality in crop-protecting bacteria is rarely investigated. Here, we uncover the role of ClpXP in Lysobacter enzymogenes, an environmental bacterial predator of crop fungal pathogens. We showed that ClpXP, as represented by ClpP, was involved in the antagonistic interaction between L. enzymogenes and a pear fungal pathogen, Valsa pyri. We found that ClpP is required for the full antifungal activity against V. pyri by affecting the secretion of a secondary antifungal metabolite (heat-stable antifungal factor, HSAF), the formation of twitching motility to help its infection to fungal mycelium, and the production of extracellular protease to degrade fungal cells. Together, our findings uncover key unidentified roles of the widespread bacterial ClpXP protease in a crop-protecting bacterium, expanding the diversified functionality of ClpXP from crop-pathogenic to protecting bacteria, particularly in crop bacterial-fungal antagonistic interaction.