In maize, at least two flavonoid biosynthetic pathways have been characterized that are regulated independently. One pathway results in 3-hydroxy flavonoids such as anthocyanins purple pigment, whereas the other pathway produces 3-deoxy flavonoids such as the phlobaphene red pigment accumulated in kernel pericarp, silks and cob.
Whereas the anthocyanin pathway and its physiological functions in plant are well documented, little is known about phlobaphenes. One of the reasons is that this family of flavonoids is not synthesized in Arabidopsis thaliana, the model plant for genetic and molecular biology. Moreover, breeders selected maize without phlobaphenes for food industry (sweet corn), because it alters the taste of the kernels for consumers. Phlobaphene biosynthesis results from the oxidation of colorless flavan-4-ol monomers or polymers. In the lab we are studying the phlobaphene biosynthesis and regulation, and their impact on seed growth and development. Knowledge acquired from phlobaphene metabolism and biological function can be used as a new tool for improving maize seed quality and biomass production.