Characterization of AvrHah1, a novel AvrBs3-like effector from Xanthomonas gardneri with virulence and avirulence activity.
Many phytopathogenic bacteria inject virulence effector proteins into plant cells. To identify novel virulence effectors of the bacterial plant pathogen Xanthomonas, a worldwide collection of pepper (Capsicum annuum) pathogenic Xanthomonas strains was studied. Xanthomonas gardneri strains produced in pepper enhanced watersoaking, a phenotype that is typical of a compatible interaction. Transfer of X. gardneri library clones into a Xanthomonas euvesicatoria recipient strain revealed that enhanced watersoaking was attributable to avrHah1 (avirulence (avr) gene homologous to avrBs3 and hax2, No. 1), a novel avrBs3-like gene. avrHah1 is a novel member of the avrBs3 family that encodes tandemly arranged repeat units of both 34 and 35 amino acid lengths. Although AvrHah1 is only distantly related to AvrBs3, it was shown to trigger a Bs3-dependent hypersensitive response (HR). When fused to a nuclear export signal, AvrHah1 is no longer capable of triggering a Bs3 HR, indicating that nuclear targeting of AvrHah1 is crucial to its recognition. Phylogenetic analysis revealed that, although AvrBs3 and AvrHah1 are only distantly related, they share blocks of high homology within potentially solvent-exposed repeat units. Thus, these data suggest that the recognition specificity of AvrBs3-like proteins is predominantly determined by solvent-exposed residues, rather than by overall homology or repeat unit length.
Schornack
Sebastian
S
Institute of Biology, Martin-Luther-University Halle-Wittenberg, 06099 Halle (Saale), Germany.
Minsavage
Gerald V
GV
Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA.
Stall
Robert E
RE
Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA.
Jones
Jeffrey B
JB
Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA.
Lahaye
Thomas
T
Institute of Biology, Martin-Luther-University Halle-Wittenberg, 06099 Halle (Saale), Germany.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002212:Capsicum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D004365:Drugs, Chinese Herbal; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005838:Genotype; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D014026:Nicotiana / Q000378:metabolism / Q000382:microbiology; D014774:Virulence; D014974:Xanthomonas / Q000378:metabolism* / Q000472:pathogenicity*
D001426:Bacterial Proteins; D004365:Drugs, Chinese Herbal; C476037:PHY 906