Paulus F, Canaday J, Vincent F, Bonnard G, Kares C, Otten L
Institut de Biologie Moléculaire des Plantes du C.N.R.S., Strasbourg, France.
Plant Mol Biol. 1991 Apr;16(4):601-14. doi: 10.1007/BF00023425.
The TA regions of biotype III octopine/cucumopine (OC) Ti plasmids are closely related to the TL region of the biotype I octopine Ti plasmids pTiAch5 and pTi15955. Sequence analysis shows that the limited and wide host range biotype III OC TA regions are derived from a common ancestor structure which lacked the 6a gene found in the biotype I octopine TL region. The TA region of the wide host range OC Ti plasmids has conserved most of the original TL-like structure. In most wide host range OC isolates the TA-iaaH gene is inactivated by the insertion of an IS866 element. However, the TA region of the wide host range isolate Hm1 carries an intact TA-iaaH gene. This gene encodes a biologically active product, as shown by root induction tests and indole-3-acetic acid measurements. The limited host range OC Ti plasmids pTiAB3 and pTiAg57 have shorter TA regions which are derived from a wide host range TA region. The AB3 type arose by an IS868-mediated, internal TA region deletion which removed the iaa genes and part of the ipt gene and left a copy of IS868 at the position of the deleted fragment. The pTiAB3 iaa/ipt deletion was followed by insertion of a second IS element, IS869, immediately 3' of the ipt gene. pTiAg57 underwent the same iaa-ipt deletion as pTiAB3, but lacks the IS868 and IS869 elements. Analysis of the various TA region structures provides a detailed insight into the evolution of the biotype III OC strains.
生物型III章鱼碱/黄瓜碱（OC）Ti质粒的TA区域与生物型I章鱼碱Ti质粒pTiAch5和pTi15955的TL区域密切相关。序列分析表明，有限宿主范围和广泛宿主范围的生物型III OC TA区域源自一个共同的祖先结构，该结构缺乏生物型I章鱼碱TL区域中发现的6a基因。广泛宿主范围OC Ti质粒的TA区域保留了大部分原始的TL样结构。在大多数广泛宿主范围的OC分离株中，TA-iaaH基因因IS866元件的插入而失活。然而，广泛宿主范围分离株Hm1的TA区域携带完整的TA-iaaH基因。如根诱导试验和吲哚-3-乙酸测量所示，该基因编码一种生物活性产物。有限宿主范围的OC Ti质粒pTiAB3和pTiAg57具有较短的TA区域，它们源自广泛宿主范围的TA区域。AB3型是由IS868介导的TA区域内部缺失产生的，该缺失去除了iaa基因和部分ipt基因，并在缺失片段的位置留下了一个IS868拷贝。pTiAB3的iaa/ipt缺失之后，在ipt基因的3'端立即插入了第二个IS元件IS869。pTiAg57经历了与pTiAB3相同的iaa-ipt缺失，但缺少IS868和IS869元件。对各种TA区域结构的分析为生物型III OC菌株的进化提供了详细的见解。
