ISSN:
1617-4623
Keywords:
Anthocyanin and proanthocyanidin biosynthesis
;
Barley
;
Dihydroquercetin reductase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary A full-length cDNA clone encoding barley dihydroflavonol-4-reductase was isolated from a kernel-specific eDNA library by screening with the cDNA of the structural gene (A1) for this enzyme from maize. Subsequently, the gene corresponding to the barley d-hydroflavonol-4-reductase cDNA was cloned and sequenced. The gene contains three introns at the same positions as in the Zea mays gene, corresponding to the positions of the first three of the five introns present in the genes of Petunia hybrida and Antirrhinum majus. In vitro transcription and translation of the Hordeum vulgare cDNA clone yielded a protein which converts dihydroquercetin into 2,3-trans-3,4-cis-leucocyanidin with NADPH as cofactor. The protein has a deduced amino acid sequence of 354 residues and a molecular weight of 38400 daltons. Dihydroflavonol reductases of barley, maize, petunia and snapdragon are highly polymorphic in the NH2 − and C-terminal parts of the polypeptide chain while a central region of 324 residues contains 51% identical amino acids. This identity increases to 81 % when only the barley and maize enzymes are compared. Recessive mutants in the Ant18 gene tested so far lack dihydroflavonol-4-reductase activity and accumulate small amounts of dihydroquercetin but have retained activity for at least two other enzymes in the flavonoid pathway. In testa-pericarp tissue of mutants ant18–159, antl8–162 and ant18–164, wild-type levels of steady state mRNA for dihydroflavonol reductase have been measured, while mRNA for this enzyme is not transcribed in mutant ant18–161. These data are consistent with the proposal that the Ant18 locus carries the structural gene for dihydroflavonol-4-reductase of barley.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00290650
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