A DNA encoding a flavone synthase that synthesizes flavones from flavanones, vectors containing said DNAs, and plants expressing same are disclosed. Methods of producing the protein which synthesizes flavones from flavanones, methods of altering the composition of flavonoids or the amount of flavonoids in a plant, methods of altering flower color and plant photosensitivity, and methods of controlling interactions between plants expressing the protein and microorganisms are also disclosed.