Plant-inducible virulence promoter of the Agrobacterium tumefaciens Ti plasmid

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, 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.

Validity Assessment of the Detection Method of Maize Event Bt10 through Investigation of Its Molecular Structure

In March 2005, the United States authorities informed the European Commission of the inadvertent release of an unauthorized maize GM Event, Bt10, in their market and subsequently the grain channel. In the United States measures were taken to eliminate Bt10 from seed and grain supplies; in the European Union an embargo for maize gluten and brewer¿s grain import was implemented unless certified of Bt10 absence with a Bt10 specific PCR detection method. With the aim of assessing the validity of the Bt10 detection method, an in-depth analysis of the molecular organization of the genetic modification of this event was carried out by both the company Syngenta, who produced the Event, and the European Commission Joint Research Centre who validated the detection method. Using a variety of molecular analytical tools, both organizations found the genetic modification of Event Bt10 to be very complex in structure, with re-arrangements, inversions and multiple copies of the structural elements (cry1Ab, pat and the amp gene), interspersed with small genomic maize fragments. Southern blot analyses demonstrated that all Bt10 elements were found tightly linked on one large fragment, including the region that would generate the event specific PCR amplicon of the Bt10 detection method. This study proposes a hypothetical map of the insert of Event Bt10 and concludes that the validated detection method for Event Bt10 is fit for its purpose.JRC.I.3-Molecular Biology and Genomic