title: The Magnaporthe oryzae effector AvrPiz-t targets the RING E3 ubiquitin ligase APIP6 to suppress pathogen-associated molecular pattern-triggered immunity in rice.
abstract: Although the functions of a few effector proteins produced by bacterial and oomycete plant pathogens have been elucidated in recent years, information for the vast majority of pathogen effectors is still lacking, particularly for those of plant-pathogenic fungi. Here, we show that the avirulence effector AvrPiz-t from the rice blast fungus Magnaporthe oryzae preferentially accumulates in the specialized structure called the biotrophic interfacial complex and is then translocated into rice (Oryza sativa) cells. Ectopic expression of AvrPiz-t in transgenic rice suppresses the flg22- and chitin-induced generation of reactive oxygen species (ROS) and enhances susceptibility to M. oryzae, indicating that AvrPiz-t functions to suppress pathogen-associated molecular pattern (PAMP)-triggered immunity in rice. Interaction assays show that AvrPiz-t suppresses the ubiquitin ligase activity of the rice RING E3 ubiquitin ligase APIP6 and that, in return, APIP6 ubiquitinates AvrPiz-t in vitro. Interestingly, agroinfection assays reveal that AvrPiz-t and AvrPiz-t Interacting Protein 6 (APIP6) are both degraded when coexpressed in Nicotiana benthamiana. Silencing of APIP6 in transgenic rice leads to a significant reduction of flg22-induced ROS generation, suppression of defense-related gene expression, and enhanced susceptibility of rice plants to M. oryzae. Taken together, our results reveal a mechanism in which a fungal effector targets the host ubiquitin proteasome system for the suppression of PAMP-triggered immunity in plants.
authors.affiliation: Department of Plant Pathology, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Chan-Ho
authors.initials: CH
authors.lastname: Park
authors.forename: Songbiao
authors.initials: S
authors.lastname: Chen
authors.forename: Gautam
authors.initials: G
authors.lastname: Shirsekar
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Khang
authors.forename: Pattavipha
authors.initials: P
authors.lastname: Songkumarn
authors.forename: Ahmed J
authors.initials: AJ
authors.lastname: Afzal
authors.forename: Yuese
authors.initials: Y
authors.lastname: Ning
authors.forename: Ruyi
authors.initials: R
authors.lastname: Wang
authors.forename: Maria
authors.initials: M
authors.lastname: Bellizzi
authors.forename: Barbara
authors.initials: B
authors.lastname: Valent
authors.forename: Guo-Liang
authors.initials: GL
authors.lastname: Wang
mesh_terms: D001483:Base Sequence; D001692:Biological Transport; D060467:Disease Resistance; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D020082:Magnaporthe / Q000472:pathogenicity / Q000502:physiology*; D012275:Oryza / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D018515:Plant Leaves; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021381:Protein Transport; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D051192:Receptors, Pattern Recognition / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D051192:Receptors, Pattern Recognition; D044767:Ubiquitin-Protein Ligases