title: Avirulence proteins AvrBs7 from Xanthomonas gardneri and AvrBs1.1 from Xanthomonas euvesicatoria contribute to a novel gene-for-gene interaction in pepper.
abstract: A novel hypersensitive resistance (HR) in Capsicum baccatum var. pendulum against the bacterial spot of pepper pathogen, Xanthomonas gardneri, was introgressed into C. annuum cv. Early Calwonder (ECW) to create the near-isogenic line designated as ECW-70R. A corresponding avirulence gene avrBs7, in X. gardneri elicited a strong HR in ECW-70R. A homolog of avrBs7, avrBs1.1, was found in X. euvesicatoria 85-10, which showed delayed HR on ECW-70R leaves. Genetic analysis confirmed the presence of a single dominant resistance gene, Bs7, corresponding to the two avr genes. Both AvrBs7 and AvrBs1.1 share a consensus protein tyrosine phosphatase (PTP) active site domain and can dephosphorylate para-nitrophenyl phosphate. Mutation of Cys(265) to Ser in the PTP domain and subsequent loss of enzymatic activity and HR activity indicated the importance of the PTP domain in the recognition of the Avr protein by the Bs7 gene transcripts. Superpositioning of AvrBs7 and AvrBs1.1 homology models indicated variation in the geometry of the loops adjacent to the active sites. These predicted structural differences might be responsible for the differences in HR timing due to differential activation of the resistance gene. Mutating the PTP domain of AvrBs1.1 to match that of AvrBs7 failed to activate HR on ECW-70R, indicating the possibility of differential substrate specificities between AvrBs1.1 and AvrBs7.
authors: Department of Plant Pathology, University of Florida, Gainesville, FL, USA.
authors: Neha
authors: N
authors: Potnis
authors: Gerald
authors: G
authors: Minsavage
authors: J Kennon
authors: JK
authors: Smith
authors: Jason C
authors: JC
authors: Hurlbert
authors: David
authors: D
authors: Norman
authors: Rosana
authors: R
authors: Rodrigues
authors: Robert E
authors: RE
authors: Stall
authors: Jeffrey B
authors: JB
authors: Jones
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002212:Capsicum / Q000276:immunology / Q000382:microbiology*; D020134:Catalytic Domain / Q000235:genetics*; D060467:Disease Resistance / Q000235:genetics; D015870:Gene Expression; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D013997:Time Factors; D014774:Virulence; D014974:Xanthomonas / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity* / Q000502:physiology
chemical_list: C587638:AvrBs1.1 protein, Xanthomonas gardneri; C587639:AvrBs7 protein, Xanthomonas gardneri; D001426:Bacterial Proteins