Phytoalexin synthesis in soybean (Glycine max)

Rapid, transient increases in mRNA activities related to phytoalexin synthesis were observed after inoculation of soybean seedlings ( Glycine max ) with the fungus, Phytophthora megasperma f. sp. glycinea , or treatment of cultured soybean cells with an elicitor preparation from the same fungus. The time courses of changes in activity were similar for mRNAs coding for enzymes of general phenylpropanoid metabolism and for chalcone synthase mRNA in both systems. Cloned cDNA was used to demonstrate that the induced changes in chalcone synthase mRNA activity coincided with changes in amount of mRNA. The results suggest that phytoalexin synthesis, one mechanism of induced resistance of plants to pathogens, is regulated by temporary gene activation.