PRINCIPLES AND BACKGROUND FOR THE CONSTRUCTION OF TRANSGENIC PLANTS DISPLAYING MULTIPLE VIRUS-RESISTANCE

We investigated the possibility of reconstructing the 2'-5' oligoadeny late (2-5A) pathway into the plant kingdom to achieve multiple virus r esistance. Differently phosphorylated 2-5A trimers and tetramers inhib ited TMV RNA translation in cell-free systems. In wheat germ extracts the most potent inhibitors were nonphosphorylated forms of 2-5A. Triph osphorylated forms of 2-5A were deposphorylated and hydrolysed in plan t extracts. Since we could not detect homologous DNA to mammalian 2-5A synthetase cDNA in tobacco or potato, we cloned rat 2-5A synthetase c DNA and transformed it by the Agrobacterium-mediated mechanism into to bacco and potato. Transformed tobacco plants were resistant to PVS inf ection and propagation of PVX was reduced. In transgenic potatoes tole rance to PVX and, in one transgenic clone, also to PVY was observed.