title: Identification of a family of avirulence genes from Xanthomonas oryzae pv. oryzae.
abstract: Races of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice, interact with cultivars of rice in a gene-for-gene specific manner. Multiple DNA fragments of various sizes from all strains of X. o. pv. oryzae hybridized with avrBs3, an avirulence gene from Xanthomonas campestris pv. vesicatoria, in Southern blots; this suggests the presence of several homologs and possibly a gene family. A genomic library of a race 2 strain of X. o. pv. oryzae, which is avirulent on rice cultivars carrying resistance genes xa-5, Xa-7, and Xa-10, was constructed. Six library clones, which hybridized to avrBs3, altered the interaction phenotype with rice cultivars carrying either xa-5, Xa-7, or Xa-10 when present in a virulent race 6 strain. Two avirulence genes, avrXa7 and avrXa10, which correspond to resistance genes Xa-7 and Xa-10, respectively, were identified and partially characterized from the hybridizing clones. On the basis of transposon insertion mutagenesis, sequence homology, restriction mapping, and the presence of a repeated sequence, both genes are homologs of avirulence genes from dicot xanthomonad pathogens. Two BamHI fragments that are homologous to avrBs3 and correspond to avrXa7 and avrXa10 contain a different number of copies of a 102-bp direct repeat. The DNA sequence of avrXa10 is nearly identical to avrBs3. We suggest that avrXa7 and avrXa10 are members of an avirulence gene family from xanthomonads that control the elicitation of resistance in mono- and dicotyledonous plants.
authors.affiliation: Department of Plant Pathology, Kansas State University, Manhattan 66506-5502.
authors.forename: C M
authors.initials: CM
authors.lastname: Hopkins
authors.forename: F F
authors.initials: FF
authors.lastname: White
authors.forename: S H
authors.initials: SH
authors.lastname: Choi
authors.forename: A
authors.initials: A
authors.lastname: Guo
authors.forename: J E
authors.initials: JE
authors.lastname: Leach
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial; D004790:Enzyme Induction; D005798:Genes, Bacterial; D017343:Genes, Plant; D008969:Molecular Sequence Data; D005810:Multigene Family; D009693:Nucleic Acid Hybridization; D012275:Oryza / Q000382:microbiology; D009195:Peroxidase / Q000096:biosynthesis; D015534:Trans-Activators; D000071336:Transcription Activator-Like Effectors; D014774:Virulence / Q000235:genetics; D014974:Xanthomonas / Q000235:genetics* / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D015534:Trans-Activators; D000071336:Transcription Activator-Like Effectors; C079054:avrXa10 protein, Xanthomonas; C073876:avrBs3-2 protein, Xanthomonas campestris; D009195:Peroxidase; D004262:DNA Restriction Enzymes