Okker R J, Spaink H, Hille J, van Brussel T A, Lugtenberg B, Schilperoort R A
Nature. 1984;312(5994):564-6. doi: 10.1038/312564a0.
Agrobacterium tumefaciens is the causative agent of crown gall, a plant tumour that can arise on most species of dicotyledonous plants. The tumour-inducing capacity of the bacterium requires the presence of a large plasmid, designated the Ti plasmid, which itself contains two regions essential for tumour formation-the T(umour)-region and the Vir(ulence)-region. The T-region is transferred to plant cells by an unknown mechanism, and becomes stably integrated into the plant genome. The Vir-region has been identified by transposon mutagenesis, but the DNA of this region has never been detected in tumour lines. However, trans-complementation of Vir mutants indicates that genes of the Vir-region are functional in the bacterium. Moreover, the Vir- and T-regions can be physically separated in A. tumefaciens without loss of tumour-inducing capacity. Seven loci, designated virA-F and virO (refs 17, 20-22), have been identified in the Vir-region of the octopine Ti plasmid, but their functions are unknown. As virC mutants in the octopine-type plasmid pTiB6 are invariably avirulent in tests on various plant species, this gene seems to be essential for virulence and we are studying it in detail. We report here that the promoter of virC shows no detectable activity in A. tumefaciens and Escherichia coli K-12 grown in standard medium, but that its activity is induced by a plant product.
根癌土壤杆菌是冠瘿病的病原体，冠瘿病是一种可在大多数双子叶植物物种上出现的植物肿瘤。该细菌的致瘤能力需要一种大型质粒的存在，这种质粒被称为Ti质粒，它本身包含肿瘤形成所必需的两个区域——T（肿瘤）区域和Vir（毒性）区域。T区域通过一种未知机制转移到植物细胞中，并稳定地整合到植物基因组中。Vir区域已通过转座子诱变鉴定出来，但在肿瘤系中从未检测到该区域的DNA。然而，Vir突变体的反式互补表明Vir区域的基因在细菌中是有功能的。此外，在根癌土壤杆菌中，Vir区域和T区域可以在物理上分离而不丧失致瘤能力。在章鱼碱型Ti质粒的Vir区域中已鉴定出七个位点，分别命名为virA - F和virO（参考文献17、20 - 22），但其功能尚不清楚。由于章鱼碱型质粒pTiB6中的virC突变体在对各种植物物种的测试中总是无毒的，这个基因似乎对毒性至关重要，我们正在对其进行详细研究。我们在此报告，virC的启动子在标准培养基中生长的根癌土壤杆菌和大肠杆菌K - 12中没有可检测到的活性，但其活性可被一种植物产物诱导。
