Nematicidal Activity and Action Receptor of a Methyl‐Accepting Chemotaxis Protein from the Phytopathogen Pseudomonas syringae against Caenorhabditis elegans

The conventional phytopathogen Pseudomonas syringae has been identified several significant virulence determinants against Caenorhabditis elegans, but their mechanisms of action remain elusive. Here, we report the nematicidal activity and action receptor of a methyl-accepting chemotaxis protein (MCP03) of a wild-type P. syringae MB03 against C. elegans. Purified MCP03 exhibited significant nematicidal toxicity against C. elegans, with a half-lethal concentration of 124.4 μg mL1, and detrimental effects on the growth and brood size of C. elegans. Additionally, MCP03-treated worms showed severe pathological destruction of the intestine and ovary, and depressed wrinkles of the cuticle. Through yeast two-hybrid assays, we identified a subunit of a COP9 signalosome, namely CSN-5, functionated as an action receptor of MCP03. In vitro pull-down and in vivo co-localization assays verified the binding interaction between MCP03 and CSN-5. RNA interference assays confirmed that MCP03 acts on CSN-5 to adversely affect the brood size, growth, and cuticle integrity of C. elegans. Following MCP03 infection, the expression of several genes relative to reproduction, growth, and cuticle formation, such as kgb-1, unc-98, and col-117, were significantly downregulated, which implicated the pathological changes of MCP03-treated nematodes. Thus, this study demonstrates that MCP03 acted on the receptor protein CSN-5 causing lethality and detrimental effects on the fertility, growth, and morphogenesis of C. elegans, which will provide new insights into the signaling pathways and mechanism underlying the nematicidal action of MCP03 towards C. elegans.