title: The type III effector AvrXccB in Xanthomonas campestris pv. campestris targets putative methyltransferases and suppresses innate immunity in Arabidopsis.
abstract: Xanthomonas campestris pv. campestris (Xcc) causes black rot, one of the most important diseases of brassica crops worldwide. The type III effector inventory plays important roles in the virulence and pathogenicity of the pathogen. However, little is known about the virulence function(s) of the putative type III effector AvrXccB in Xcc. Here, we investigated the immune suppression ability of AvrXccB and the possible underlying mechanisms. AvrXccB was demonstrated to be secreted in a type III secretion system-dependent manner. AvrXccB tagged with green fluorescent protein is localized to the plasma membrane in Arabidopsis, and the putative N-myristoylation motif is essential for its localization. Chemical-induced expression of AvrXccB suppresses flg22-triggered callose deposition and the oxidative burst, and promotes the in planta growth of Xcc and Pseudomonas syringae pv. tomato in transgenic Arabidopsis plants. The putative catalytic triad and plasma membrane localization of AvrXccB are required for its immunosuppressive activity. Furthermore, it was demonstrated that AvrXccB interacts with the Arabidopsis S-adenosyl-l-methionine-dependent methyltransferases SAM-MT1 and SAM-MT2. Interestingly, SAM-MT1 is not only self-associated, but also associated with SAM-MT2 in vivo. SAM-MT1 and SAM-MT2 expression is significantly induced upon stimulation of microbe-associated molecular patterns and bacterial infection. Collectively, these findings indicate that AvrXccB targets a putative methyltransferase complex and suppresses plant immunity.
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Yanping
authors.identifier: 0000-0001-5803-5343
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Fuhao
authors.initials: F
authors.lastname: Cui
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Anfei
authors.initials: A
authors.lastname: Fang
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Shanzhi
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Jiyang
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wei
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Plant Pathology, Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
authors.forename: Wenxian
authors.initials: W
authors.lastname: Sun
mesh_terms: D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology*; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D057865:Plant Immunity / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016959:Xanthomonas campestris / Q000276:immunology* / Q000378:metabolism* / Q000472:pathogenicity*
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D008780:Methyltransferases
keywords: AvrXccB; S-adenosyl-l-methionine-dependent methyltransferase; Xanthomonas campestris pv. campestris; plant immunity; type III effector