Genetic and structural characterization of the avirulence gene avrBs3 from Xanthomonas campestris pv. vesicatoria |
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| Authors: | Ulla Bonas Robert E Stall and Brian Staskawicz |
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| Institution: | (1) Department of Plant Pathology, University of California, 94720 Berkeley, CA, USA;(2) Department of Plant Pathology, University of Florida, 32611 Gainesville, FI, USA;(3) Present address: Institut für Genbiologische Forschung GmbH, Thnestr. 63, 1000 Berlin 33, Federal Republic of Germany |
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| Abstract: | Summary The avirulence gene avrBs3 from Xanthomonas campestris pv. vesicatoria was cloned and found to be localized on a self-transmissable plasmid. Genetic analysis of an avrBs3 insertion mutation revealed that avrBs3 constitutes a single locus, specifying the resistant phenotype on pepper plants. Southern blot experiments showed that no DNA sequences homologous to avrBs3 were present in other races of X. c. pv. vesicatoria, which are unable to induce a hypersensitive reaction on ECW-30R. However, the DNA of several different pathovars of X. campestris hybridized to the avrBs3 probe. A deletion analysis defined a region of 3.6–3.7 kb essential for avrBs3 activity. The nucleotide sequence of this region was determined. A 3561 nucleotide open reading frame (ORF1), encoding a 125000 dalton protein, was found in the 3.7 kb region that was sufficient for avrBs3 activity. A second long ORF (2351 nucleotides) was identified on the other strand. A remarkable feature of both ORFs is the presence of 17 direct repeats of 102 bp which share 91%–100% homology with each other. |
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| Keywords: | Xanthomonas campestris Avirulence gene Disease resistance DNA sequence Deletion analysis |
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