Clare B G, Kerr A, Jones D A
Department of Plant Pathology, University of Adelaide, Glen Osmond, South Australia, Australia.
Plasmid. 1990 Mar;23(2):126-37. doi: 10.1016/0147-619x(90)90031-7.
Wild-type Agrobacterium radiobacter strain 84 and its Tra- derivative K1026, used for biological control of crown gall disease, each contain the plasmid pAtK84b. It confers incompatibility to tumor-inducing (Ti) plasmids of pathogenic A. tumefaciens, thus preventing transfer of Ti plasmids into K84 and K1026, and the consequent development of pathogens resistant to the specific antibiotic, agrocin 84 produced by K84 and K1026. pAtK84b also resembles one group of Ti plasmids in its capacity for directing nopaline catabolism. A study of the DNA homology among pAtK84b, pTiC58, and pTiAch5 was carried out. pAtK84b was transferred by conjugation to a plasmidless recipient and, after isolation, was hybridized with Ti plasmid DNA. Areas of DNA homology were located on published maps of pTiC58 and pTiAch5, a restriction enzyme map of pAtK84b was constructed, and areas of homology with DNA of known genetic function were located on the map. Strong and extensive (over 50%) homology was found between pAtK84b and pTiC58 (nopaline catabolic, Noc), but much less between pAtK84b and pTiAch5 (octopine catabolic). There was no detectable homology between pAtK84b and the oncogenic T-DNA and virulence (Vir) regions of either Ti plasmid. The size of pAtK84b was 173 kb and the orientation of regions of identified gene function (Noc, incompatability/origin of replication, and conjugal transfer) on pTiC58 was matched by the locations of homologous areas on pAtK84b. It is concluded that pAtK84b may be a deletion product of a pTiC58-type plasmid which has been disarmed in the oncogenic T-DNA and Vir regions.
用于防治冠瘿病的野生型放射土壤杆菌菌株84及其无接合转移能力的衍生菌株K1026均含有质粒pAtK84b。它可使致病根癌土壤杆菌的致瘤（Ti）质粒不相容，从而阻止Ti质粒转移到K84和K1026中，以及防止随后产生对K84和K1026产生的特异性抗生素农杆素84耐药的病原体。pAtK84b在指导胭脂碱分解代谢的能力方面也类似于一组Ti质粒。开展了对pAtK84b、pTiC58和pTiAch5之间DNA同源性的研究。通过接合作用将pAtK84b转移到无质粒受体中，分离后与Ti质粒DNA杂交。在已发表的pTiC58和pTiAch5图谱上确定了DNA同源区域，构建了pAtK84b的限制性酶切图谱，并在该图谱上确定了与已知基因功能DNA的同源区域。发现pAtK84b与pTiC58（胭脂碱分解代谢，Noc）之间存在强烈且广泛（超过50%）的同源性，但pAtK84b与pTiAch5（章鱼碱分解代谢）之间的同源性要低得多。pAtK84b与任何一种Ti质粒的致癌性T-DNA和毒力（Vir）区域之间均未检测到同源性。pAtK84b的大小为173 kb，pAtK84b上已鉴定基因功能区域（Noc、不相容性/复制起点和接合转移）的方向与pTiC58上同源区域的位置相匹配。得出的结论是，pAtK84b可能是pTiC58型质粒的缺失产物，该质粒在致癌性T-DNA和Vir区域已被解除武装。
