Apigenin produced by maize flavone synthase I and II protects plants against UV-B-induced damage

RIGHINI ARAMBURU, SILVANA; RODRIGUEZ, EDUARDO; BEROSICH, CARLA; GROTEWOLD, ERICH; CASATI, PAULA; FALCONE FERREYRA, MARIA

Plant Cell Enviroment

Wiley Online Library

Lugar: New Jersey; Año: 2018 vol. 42 p. 495 - 508

1365-3040

Flavones, ones of the largest group of flavonoids, have beneficial effects on human health and are considered of high nutritional value. Previously, we demonstrated that ZmFNSI is one of the enzymes responsible for the synthesis of O-glycosyl flavones in floral maize tissues; however, in related species like rice and sorghum, FNSII type enzymes also contribute to flavone biosynthesis. In this work, by recombinant protein activity assays, transgenic plant analysis, and gene expression and regulation studies, we provide evidence that maize plants have both one FNSI and one FNSII type flavone synthases. Arabidopsis transgenic plants expressing each FNS enzyme were generated to validate the role of flavones protecting plants against UV-B radiation. We here demostrate that ZmCYP93G7 (FNSII) has flavone synthase activity and is able to complement the Arabidopsis dmr6 mutant, restoring the susceptibility to Pseudomonas syringae. ZmFNSII expression is controlled by the C1/PL1 + R/B anthocyanin transcriptional complexes; and both ZmFNSI and ZmFNSII are regulated by UV-B. After UV-B exposure, Arabidopsis transgenic plants expressing ZmFNSI or ZmFNSII that accumulate apigenin show less UV-B-induced damage than wild type plants. Together, we show that maize has two FNS type enzymes that participate in the synthesis of apigenin, confering protection against UV-B radiation.