Cloning and Characterization of a UV-B Inducible Maize Flavonol Synthase

MA LORENA FALCONE FERREYRA; SEBASTIAN RIUS; JULIA EMILIANI; LUCILLE POURCEL; ANTJE FELLER; KENGO MOROHASHI; KEN RIEDL; STEVEN SCHWARTZ; PAULA CASATI; ERICH GROTEWOLD

PLANT JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 62 p. 77 - 91

0960-7412

Flavonols are important compounds for conditional male fertility in maize (Zea mays) and other crops, and theyalso contribute to protecting plants from UV-B radiation. However, little continues to be known on how maizeand other grasses synthesize flavonols, and how flavonol biosynthesis is regulated. By homology with anArabidopsis flavonol synthase (AtFLS1), we cloned a maize gene encoding a protein (ZmFLS1) capable ofconverting the dihydrokaempferol (DHK) and dihydroquercetin (DHQ) dihydroflavonols to the correspondingflavonols, kaempferol (K) and quercetin (Q). Moreover, ZmFLS1 partially complements the flavonol deficiencyof the Arabidopsis fls1 mutant, and restores anthocyanin accumulation to normal levels. We demonstrate thatZmFLS1 is under the control of the anthocyanin (C1/PL1 + R/B) and 3-deoxy flavonoid (P1) transcriptionalregulators. Indeed, using chromatin immunoprecipitation (ChIP) experiments, we establish that ZmFLS1 is animmediate direct target of the P1 and C1/R regulatory complexes, revealing similar control as for earlier stepsin the maize flavonoid pathway. Highlighting the importance of flavonols in UV-B protection, we also showthat ZmFLS1 is induced in maize seedlings by UV-B, and that this induction is in part mediated by the increasedexpression of the P1, B and PL1 regulators. Together, our results identify a key flavonoid biosynthetic enzymeso far missed in maize and other monocots, and illustrate mechanisms by which flavonol accumulation iscontrolled in maize.