Reference "Structure of the Hordeum vulgare gene encoding dihydroflavonol-4-reductase and molecular analysis of ant18 mutants blocked in flavonoid synthesis"

Reference ID

8622

Title

Structure of the Hordeum vulgare gene encoding dihydroflavonol-4-reductase and molecular analysis of ant18 mutants blocked in flavonoid synthesis

Source

Molecular & General Genetics, 1991, vol. 230, pp. 49-59

Authors (2)

Kristiansen-K-N

Rohde-W

Abstract

A full-length cDNA clone encoding barley dihydroflavonol-4-reductase was
isolated from a kernel-specific cDNA library by screening with the cDNA of the
structural gene (A1) for this enzyme from maize. Subsequently, the gene
corresponding to the barley dihydroflavonol-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 38,400 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,
ant18-162 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.