title: The Activation of Phytophthora Effector Avr3b by Plant Cyclophilin is Required for the Nudix Hydrolase Activity of Avr3b.
abstract: Plant pathogens secrete an arsenal of effector proteins to impair host immunity. Some effectors possess enzymatic activities that can modify their host targets. Previously, we demonstrated that a Phytophthora sojae RXLR effector Avr3b acts as a Nudix hydrolase when expressed in planta; and this enzymatic activity is required for full virulence of P. sojae strain P6497 in soybean (Glycine max). Interestingly, recombinant Avr3b produced by E. coli does not have the hydrolase activity unless it was incubated with plant protein extracts. Here, we report the activation of Avr3b by a prolyl-peptidyl isomerase (PPIase), cyclophilin, in plant cells. Avr3b directly interacts with soybean cyclophilin GmCYP1, which activates the hydrolase activity of Avr3b in a PPIase activity-dependent manner. Avr3b contains a putative Glycine-Proline (GP) motif; which is known to confer cyclophilin-binding in other protein substrates. Substitution of the Proline (P132) in the putative GP motif impaired the interaction of Avr3b with GmCYP1; as a result, the mutant Avr3bP132A can no longer be activated by GmCYP1, and is also unable to promote Phytophthora infection. Avr3b elicits hypersensitive response (HR) in soybean cultivars producing the resistance protein Rps3b, but Avr3bP132A lost its ability to trigger HR. Furthermore, silencing of GmCYP1 rendered reduced cell death triggered by Avr3b, suggesting that GmCYP1-mediated Avr3b maturation is also required for Rps3b recognition. Finally, cyclophilins of Nicotiana benthamiana can also interact with Avr3b and activate its enzymatic activity. Overall, our results demonstrate that cyclophilin is a "helper" that activates the enzymatic activity of Avr3b after it is delivered into plant cells; as such, cyclophilin is required for the avirulence and virulence functions of Avr3b.
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Guanghui
authors: G
authors: Kong
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Yao
authors: Y
authors: Zhao
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Maofeng
authors: M
authors: Jing
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Jie
authors: J
authors: Huang
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Jin
authors: J
authors: Yang
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Yeqiang
authors: Y
authors: Xia
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Liang
authors: L
authors: Kong
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Wenwu
authors: W
authors: Ye
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Qin
authors: Q
authors: Xiong
authors: Department of Plant Pathology and Microbiology, University of California, Riverside, Riverside, California, United States of America; National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China.
authors: Yongli
authors: Y
authors: Qiao
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Suomeng
authors: S
authors: Dong
authors: Department of Plant Pathology and Microbiology, University of California, Riverside, Riverside, California, United States of America.
authors: Wenbo
authors: W
authors: Ma
authors: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors: Yuanchao
authors: Y
authors: Wang
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D021983:Cyclophilins / Q000276:immunology* / Q000378:metabolism; D006790:Host-Parasite Interactions / Q000502:physiology*; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity*; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology; D057865:Plant Immunity / Q000502:physiology; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism; D011755:Pyrophosphatases / Q000276:immunology* / Q000378:metabolism; D013025:Glycine max / Q000469:parasitology*; D020798:Two-Hybrid System Techniques; D014774:Virulence; D000096964:Nudix Hydrolases
chemical_list: D021983:Cyclophilins; D010940:Plant Proteins; D011755:Pyrophosphatases; D000096964:Nudix Hydrolases