title: Computational and biochemical analysis of the Xanthomonas effector AvrBs2 and its role in the modulation of Xanthomonas type three effector delivery.
abstract: Effectors of the bacterial type III secretion system provide invaluable molecular probes to elucidate the molecular mechanisms of plant immunity and pathogen virulence. In this report, we focus on the AvrBs2 effector protein from the bacterial pathogen Xanthomonas euvesicatoria (Xe), the causal agent of bacterial spot disease of tomato and pepper. Employing homology-based structural analysis, we generate a three-dimensional structural model for the AvrBs2 protein and identify catalytic sites in its putative glycerolphosphodiesterase domain (GDE). We demonstrate that the identified catalytic region of AvrBs2 was able to functionally replace the GDE catalytic site of the bacterial glycerophosphodiesterase BhGlpQ cloned from Borrelia hermsii and is required for AvrBs2 virulence. Mutations in the GDE catalytic domain did not disrupt the recognition of AvrBs2 by the cognate plant resistance gene Bs2. In addition, AvrBs2 activation of Bs2 suppressed subsequent delivery of other Xanthomonas type III effectors into the host plant cells. Investigation of the mechanism underlying this modulation of the type III secretion system may offer new strategies to generate broad-spectrum resistance to bacterial pathogens.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America.
authors.forename: Bingyu
authors.initials: B
authors.lastname: Zhao
authors.forename: Douglas
authors.initials: D
authors.lastname: Dahlbeck
authors.forename: Ksenia V
authors.initials: KV
authors.lastname: Krasileva
authors.forename: Richard W
authors.initials: RW
authors.lastname: Fong
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Staskawicz
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000502:physiology; D002212:Capsicum / Q000382:microbiology; D018551:Solanum lycopersicum / Q000382:microbiology; D008958:Models, Molecular; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D017434:Protein Structure, Tertiary; D037521:Virulence Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014974:Xanthomonas / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D037521:Virulence Factors