Kristiansen KN et al. 1991
- Authors:
Kristiansen KN. Rohde W.
- Title:
Structure of the Hordeum vulgare gene encoding dihydroflavonol-4-reductase
and molecular analysis of ant18 mutants blocked in flavonoid synthesis.
- Reference location:
Molecular & General Genetics. 230(1-2):49-59, 1991 Nov.
- 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.
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