ARS | Publication request: ISOLATION AND FUNCTIONAL CHARACTERIZATION OF A FLAVONOID 3' HYDROXYLASE CORRESPONDING TO THE RED ALEURONE 1 LOCUS OF MAIZE

Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 5, 2005
Publication Date: March 10, 2005
Citation: Svabek, C., Boddu, J., Cortes-Cruz, M., Mcmullen, M.D., Chopra, S. 2005. Isolation and functional characterization of a flavonoid 3' hydroxylase corresponding to the red aleurone 1 locus of maize [abstract]. Maize Genetics Conference. Paper No. 168. p. 122.

Technical Abstract: Anthocyanins are synthesized via the flavonoid biosynthesis pathway which produces a variety of pigmented and non-pigmented secondary metabolites. Several intermediate steps of biosynthesis of flavonoid compounds require activity of cytochrome P450 dependent enzymes. A functional red aleurone1 (pr1) locus is required for the purple (cyanidin) aleurones, whereas a mutation in pr1 leads to accumulation of red pigment (pelargonidin). Previously, Larson, Bussard and Coe (Biochem Genet. 1986, 24:615-624.) showed that functional pr1encodes or regulates a flavonoid 3’-hydroxylase (F3’H) activity responsible for B ring hydroxylation. In the anthocyanin biosynthesis pathway, this F3’H activity would thus be required to convert dihydrokaempferol (DHK) to dihydroquercitin (DHQ). We have isolated and characterized maize genomic and cDNA sequences which encode for a putative F3’H. Sequence characterization shows that the maize F3’H is a member of the super family of cytochrome P450s that catalyze NADPH- and O2-dependent hydroxylation reactions. Genetic characterization of three pr1 mutant alleles shows that the red aleurone phenotype is linked with the isolated sequence. Using a SNP marker assay, the F3’H gene maps to the pr1 position on chromosome 5. In addition to the transcriptional regulation of pr1 by transcription factors r1 and c1 in aleurones, our results indicate that pr1 expression in pericarp is regulated by the pericarp color (p) locus consistent with a role in 3-deoxyflavonoids or phlobaphene synthesis in pericarp and cob glumes. Overall, results obtained from transcript analysis, functional complementation and linkage mapping studies confirm that the putative sequence encodes for a F3’H corresponding to the pr1 locus of maize.