Development of transformation vectors based upon a modified plant alpha-tubulin gene as the selectable marker.

A plant transformation and selection system has been developed utilizing a modified tubulin gene as a selectable marker. The vector constructs carrying a mutant alpha-tubulin gene from goosegrass conferring resistance to dinitroaniline herbicides were created for transformation of monocotyledonous and dicotyledonous plants. These constructs contained beta- and/or mutant alpha-tubulin genes driven either by ubiquitin or CaMV 35S promoter. The constructs were used for biolistic transformation of finger millet and soybean or for Agrobacterium-mediated transformation of flax and tobacco. Trifluralin, the main representative of dinitroaniline herbicides, was used as a selective agent in experiments to select transgenic cells, tissues and plantlets. Selective concentrations of trifluralin estimated for each species were as follows: 10 microM for Eleusine coracana, Glycine max, Nicotiana plumbaginifolia and Nicotiana sylvestris; 3 microM for Linum usitatissimum. PCR and Southern blotting analyses of transformed lines with a specific probe to nptII, alpha-tubulin or beta-tubulin genes were performed to confirm the transgenic nature of regenerated plants. Band specific for the mutant alpha-tubulin gene was identified in transformed plant lines. Results confirmed the stable integration of the mutant tubulin gene into the plant genomes. The present study clearly demonstrates the use of a plant mutant tubulin as a selective gene for plant transformation.