The ternary transformation system: constitutive virG on a compatible plasmid dramatically increases Agrobacterium-mediated plant transformation.

This paper describes a so-called ternary transformation system for plant cells. We demonstrate that Agrobacterium tumefaciens strain LBA4404 supplemented with a constitutive virG mutant gene (virGN54D) on a compatible plasmid is capable of very efficient T-DNA transfer to a diverse range of plant species. For the plant species Catharanthus roseus it is shown that increased T-DNA transfer results in increased stable transformation frequencies. Analysis of stably transformed C. roseus cell lines showed that, although the T-DNA transfer frequency is greatly enhanced by addition of virGN54D, only one or a few T-DNA copies are stably integrated into the plant genome. Thus, high transformation frequencies of different plant species can be achieved by introduction of a ternary plasmid carrying a constitutive virG mutant into existing A. tumefaciens strains in combination with standard binary vectors.