Abstract
In Arabidopsis, proanthocyanidins specifically accumulate in the endothelium during early seed development. At least three TRANSPARENT TESTA (TT) genes, TT2, TT8, and TTG1, are necessary for the normal expression of several flavonoid structural genes in immature seed, such as DIHYDROFLAVONOL-4-REDUCTASE and BANYULS (BAN). TT8 and TTG1 were characterized recently and found to code for a basic helix-loop-helix domain transcription factor and a WD-repeat-containing protein, respectively. Here the molecular cloning of the TT2 gene was achieved by T-DNA tagging. TT2 encoded an R2R3 MYB domain protein with high similarity to the rice OsMYB3 protein and the maize COLORLESS1 factor. A TT2-green fluorescent protein fusion protein was located mostly in the nucleus, in agreement with the regulatory function of the native TT2 protein. TT2 expression was restricted to the seed during early embryogenesis, consistent with BAN expression and the proanthocyanidin deposition profile. Finally, in gain-of-function experiments, TT2 was able to induce ectopic expression of BAN in young seedlings and roots in the presence of a functional TT8 protein. Therefore, our results strongly suggest that stringent spatial and temporal BAN expression, and thus proanthocyanidin accumulation, are determined at least partially by TT2.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alleles
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Amino Acid Sequence
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Anthocyanins / biosynthesis*
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Arabidopsis / cytology
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Arabidopsis / genetics
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Arabidopsis / growth & development
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Arabidopsis / metabolism*
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Arabidopsis Proteins / chemistry*
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Base Sequence
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Basic Helix-Loop-Helix Transcription Factors
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Cell Nucleus / metabolism
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Cloning, Molecular
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DNA-Binding Proteins / chemistry*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Evolution, Molecular
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Flavonoids / biosynthesis
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Flavonoids / genetics
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Gene Expression Regulation, Developmental
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Gene Expression Regulation, Plant
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Genes, Plant / genetics*
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Genetic Complementation Test
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Molecular Sequence Data
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Mutation
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Phenotype
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Plant Roots / genetics
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Plant Roots / growth & development
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Plant Roots / metabolism
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Proanthocyanidins*
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Protein Structure, Tertiary
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Proto-Oncogene Proteins c-myb / chemistry*
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Seeds / genetics
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Seeds / growth & development
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Seeds / metabolism*
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Sequence Alignment
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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Anthocyanins
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Arabidopsis Proteins
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Basic Helix-Loop-Helix Transcription Factors
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DNA-Binding Proteins
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Flavonoids
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Nuclear Proteins
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Proanthocyanidins
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Proto-Oncogene Proteins c-myb
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TT2 protein, Arabidopsis
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TT8 protein, Arabidopsis
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Transcription Factors
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proanthocyanidin
Associated data
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GENBANK/AF062859
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GENBANK/AF062864
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GENBANK/AF062908
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GENBANK/AF146702
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GENBANK/AF175991
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GENBANK/AJ299452
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GENBANK/D10936
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GENBANK/D14712
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GENBANK/D88619
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GENBANK/L19494
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GENBANK/M15024
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GENBANK/M37153
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GENBANK/U26935
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GENBANK/U26936
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GENBANK/U39448
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GENBANK/U57002
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GENBANK/X70877
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GENBANK/X87690
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GENBANK/X90384