Title: FERONIA Receptor Kinase Contributes to Plant Immunity by Suppressing Jasmonic Acid Signaling in Arabidopsis thaliana
Abstract: Bacterial pathogens use effectors and phytotoxins to facilitate infection of host plants. Coronatine (COR) is one of the phytotoxins produced in bacterial pathogens, such as Pseudomonas syringae pv. tomato DC3000 (pst DC3000). COR structurally and functionally mimics the active form of the plant hormone jasmonic acid (JA), JA-isoleucine (JA-Ile), and can hijack the host JA-signaling pathway to achieve host disease susceptibility [1Xin X.F. He S.Y. Pseudomonas syringae pv. tomato DC3000: a model pathogen for probing disease susceptibility and hormone signaling in plants.Annu. Rev. Phytopathol. 2013; 51: 473-498Crossref PubMed Scopus (378) Google Scholar]. COR utilizes the transcription factor MYC2, a master regulator of JA signaling, to activate NAC transcription factors, which functions to inhibit accumulation of salicylic acid (SA) and thus compromise host immunity [2Zheng X.Y. Spivey N.W. Zeng W. Liu P.P. Fu Z.Q. Klessig D.F. He S.Y. Dong X. Coronatine promotes Pseudomonas syringae virulence in plants by activating a signaling cascade that inhibits salicylic acid accumulation.Cell Host Microbe. 2012; 11: 587-596Abstract Full Text Full Text PDF PubMed Scopus (386) Google Scholar]. It has been demonstrated that SA can antagonize JA signaling through NONEXPRESSOR of PATHOGENESIS-RELATED GENE1 (NPR1) [3Spoel S.H. Koornneef A. Claessens S.M. Korzelius J.P. Van Pelt J.A. Mueller M.J. Buchala A.J. Métraux J.P. Brown R. Kazan K. et al.NPR1 modulates cross-talk between salicylate- and jasmonate-dependent defense pathways through a novel function in the cytosol.Plant Cell. 2003; 15: 760-770Crossref PubMed Scopus (849) Google Scholar] and downstream transcription factors TGAs [4Zander M. La Camera S. Lamotte O. Métraux J.P. Gatz C. Arabidopsis thaliana class-II TGA transcription factors are essential activators of jasmonic acid/ethylene-induced defense responses.Plant J. 2010; 61: 200-210Crossref PubMed Scopus (151) Google Scholar] and WRKYs [5Mao P. Duan M. Wei C. Li Y. WRKY62 transcription factor acts downstream of cytosolic NPR1 and negatively regulates jasmonate-responsive gene expression.Plant Cell Physiol. 2007; 48: 833-842Crossref PubMed Scopus (109) Google Scholar, 6Li J. Brader G. Palva E.T. The WRKY70 transcription factor: a node of convergence for jasmonate-mediated and salicylate-mediated signals in plant defense.Plant Cell. 2004; 16: 319-331Crossref PubMed Scopus (859) Google Scholar]. However, the detailed mechanism by which host plants counteract COR-mediated susceptibility is largely unknown. Here, we show that the receptor kinase FERONIA (FER) functions to inhibit JA and COR signaling by phosphorylating and destabilizing MYC2, thereby positively regulating immunity. Conversely, the peptide ligand RALF23 acts through FER to stabilize MYC2 and elevate JA signaling, negatively contributing to plant immunity. Our results establish the RALF23-FER-MYC2 signaling module and provide a previously unknown mechanism by which host plants utilize FER signaling to counteract COR-mediated host disease susceptibility.