Paulus F, Canaday J, Otten L
Department of Phytopathology, Plant Molecular Biology Institute, Strasbourg, France.
Mol Plant Microbe Interact. 1991 Mar-Apr;4(2):190-7. doi: 10.1094/mpmi-4-190.
Agrobacterium tumefaciens biotype III octopine strains have been isolated from grapevine tumors worldwide. They comprise limited and wide host range (LHR and WHR) strains that carry related tumor-inducing (Ti) plasmids with two T-regions, TA and TB. The WHR TA-region resembles the biotype I octopine region, whereas the LHR TA-region is a recent deletion derivative of the WHR TA-region, which lacks the iaa genes and part of the ipt gene. Sequencing of the TA-region of the ubiquitous LHR strain AB3 showed that the deleted region is replaced by an insertion sequence (IS) element, IS868, which resembles the IS51 element of Pseudomonas syringae subsp. savastanoi. The Ti plasmid of LHR strain Ag57 carries essentially the same iaa gene deletion as pTiAB3, but lacks IS868. We propose that the LHR Ti plasmids arose by the recent insertion of an IS868 element into the TA-region of a WHR-type Ti plasmid, followed by transposition to a nearby site. The deletion was caused during the second transposition or by later recombination between the two IS868 copies. Biotype III octopine strains also carry an IS51-like sequence close to the TB iaa genes. Our results confirm and extend earlier observations indicating that IS51-like elements in Pseudomonas and Agrobacterium are associated with iaa genes and played a major role in Ti plasmid evolution.
根癌土壤杆菌生物型III章鱼碱型菌株已在全球范围内从葡萄肿瘤中分离出来。它们包括寄主范围有限和广泛的（LHR和WHR）菌株，这些菌株携带相关的致瘤（Ti）质粒，带有两个T区域，TA和TB。WHR TA区域类似于生物型I章鱼碱区域，而LHR TA区域是WHR TA区域的近期缺失衍生物，它缺少iaa基因和部分ipt基因。普遍存在的LHR菌株AB3的TA区域测序表明，缺失区域被一个插入序列（IS）元件IS868取代，该元件类似于丁香假单胞菌丁香假单胞菌亚种的IS51元件。LHR菌株Ag57的Ti质粒与pTiAB3基本具有相同的iaa基因缺失，但缺少IS868。我们提出，LHR Ti质粒是通过最近将IS868元件插入WHR型Ti质粒的TA区域，然后转座到附近位点而产生的。缺失是在第二次转座过程中或后来两个IS868拷贝之间的重组引起的。生物型III章鱼碱型菌株在靠近TB iaa基因的位置也携带一个类似IS51的序列。我们的结果证实并扩展了早期的观察结果，表明假单胞菌和土壤杆菌中的类似IS51元件与iaa基因相关，并在Ti质粒进化中起主要作用。
