Bonas U, Conrads-Strauch J, Balbo I
Institut für Genbiologische Forschung Berlin GmbH, FRG.
Mol Gen Genet. 1993 Apr;238(1-2):261-9. doi: 10.1007/BF00279555.
Bacterial spot disease of tomato and pepper caused by Xanthomonas campestris pv vesicatoria is prevented by resistance genes in the plant that match genes for avirulence in the bacterium. Based on DNA homology to the avirulence gene avrBs3, which induces the resistance response on pepper, we have isolated another avirulence gene from X. c. vesicatoria, designated avrBs3-2. This gene differs in specificity from avrBs3 in inducing the hypersensitive response on tomato but not on pepper. Sequence analysis of the avrBs3-2 gene revealed a high degree of conservation: the 3480 bp open reading frame contains an internal region of 17.5 nearly identical 102 bp repeat units that differ in their order from those present in the avrBs3 gene. The coding region is 97% identical to avrBs3 and expresses constitutively a 122 kDa protein, thus representing a natural allele of this gene. The previously isolated 1.7 kb avrBsP gene from X. c. vesicatoria is 100% identical to the corresponding avrBs3-2 sequence, indicating that these genes might be identical. Interestingly, derivatives of avrBs3-2 lacking the C-terminal region and part of the repetitive region are still able to confer incompatibility in tomato. The avrBs3-2 gene is compared with the sequence of avrBs3 derivatives generated by deletion of repeat units that also have avirulence activity on tomato. Both genes, avrBs3 and avrBs3-2, are flanked by a 62 bp long inverted repeat, which prompts speculations about the origin of the members of the avrBs3 gene family.
由野油菜黄单胞菌斑点病致病变种（Xanthomonas campestris pv vesicatoria）引起的番茄和辣椒细菌性斑点病，可被植物中与细菌无毒基因相匹配的抗性基因所预防。基于与无毒基因avrBs3的DNA同源性（该基因在辣椒上诱导抗性反应），我们从野油菜黄单胞菌斑点病致病变种中分离出了另一个无毒基因，命名为avrBs3-2。该基因在诱导番茄超敏反应方面与avrBs3的特异性不同，对辣椒则无此作用。avrBs3-2基因的序列分析显示出高度保守性：3480 bp的开放阅读框包含一个由17.5个几乎相同的102 bp重复单元组成的内部区域，这些重复单元的顺序与avrBs3基因中的不同。编码区与avrBs3有97%的同一性，并组成型表达一种122 kDa的蛋白质，因此代表了该基因的一个天然等位基因。先前从野油菜黄单胞菌斑点病致病变种中分离出的1.7 kb avrBsP基因与相应的avrBs3-2序列100%相同，表明这些基因可能是相同的。有趣的是，缺失C末端区域和部分重复区域的avrBs3-2衍生物仍能在番茄中产生不亲和性。将avrBs3-2基因与通过缺失对番茄也有无毒活性的重复单元而产生的avrBs3衍生物的序列进行了比较。avrBs3和avrBs3-2这两个基因的两侧都有一个62 bp长的反向重复序列，这引发了对avrBs3基因家族成员起源的推测。
