Methods of genetically manipulating biology active 4'-O-methylated
isoflavonoids have been found based upon the regiospecifity of isoflavone
7-OMT in vivo. Upon transformation and expression of an isoflavonoid
O-methyltransferase gene, up-regulation of IOMT in the transgenic plants
can be used to increase the accumulation of 4'-O-methylated isoflavonoid
phytolalexins, providing for increased disease resistance to the plant.
Similar methods can be used to increase accumulation of 4'-O-methylated
isoflavonoid nutraceuticals in plants. For down-regulation of IOMT in
plants that naturally make 4'O-isoflavonoid phytoalexins and
4'-O-methylated isoflavonoid nutraceuticals, IOMT gene sequences can be
transformed in the antisense orientation.