Hopkins C M, White F F, Choi S H, Guo A, Leach J E
Department of Plant Pathology, Kansas State University, Manhattan 66506-5502.
Mol Plant Microbe Interact. 1992 Nov-Dec;5(6):451-9. doi: 10.1094/mpmi-5-451.
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.
水稻白叶枯病的病原菌——稻黄单胞菌水稻致病变种（Xanthomonas oryzae pv. oryzae）的小种与水稻品种以基因对基因的特异性方式相互作用。在Southern杂交中，来自稻黄单胞菌水稻致病变种所有菌株的多个不同大小的DNA片段与来自野油菜黄单胞菌疮痂致病变种（Xanthomonas campestris pv. vesicatoria）的无毒基因avrBs3杂交；这表明存在几个同源物，可能还有一个基因家族。构建了稻黄单胞菌水稻致病变种小种2菌株的基因组文库，该菌株对携带抗性基因xa - 5、Xa - 7和Xa - 10的水稻品种无毒。六个与avrBs3杂交的文库克隆，当存在于毒性小种6菌株中时，改变了与携带xa - 5、Xa - 7或Xa - 10的水稻品种的相互作用表型。从杂交克隆中鉴定并部分表征了两个无毒基因avrXa7和avrXa10，它们分别对应于抗性基因Xa - 7和Xa - 10。基于转座子插入诱变、序列同源性、限制性图谱分析以及重复序列的存在，这两个基因都是双子叶植物黄单胞菌病原菌无毒基因的同源物。与avrBs3同源且对应于avrXa7和avrXa10的两个BamHI片段含有不同数量的102 bp直接重复序列拷贝。avrXa10的DNA序列与avrBs3几乎相同。我们认为avrXa7和avrXa10是黄单胞菌无毒基因家族的成员，该家族控制单子叶和双子叶植物中抗性的激发。
