Analysis of bHLH and MYB domain proteins: species‐specific regulatory differences are caused by divergent evolution of target anthocyanin genes

• Published in: The Plant journal : for cell and molecular biology Vol. 13; no. 4; pp. 475 - 488
• Main Authors: Quattrocchio, Francesca, Wing, John F., Va, Karel, De, Woude, Mol, Joseph N. M., Koes, Ronald
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01-02-1998; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Anthocyanins - biosynthesis; Anthocyanins - genetics; Base Sequence; Biological and medical sciences; Chromosome Mapping; Cloning, Molecular; DNA Primers - genetics; DNA-Binding Proteins - genetics; Economic plant physiology; Evolution, Molecular; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes, Plant; Helix-Loop-Helix Motifs - genetics; Metabolism; Molecular Sequence Data; Nitrogen metabolism and other ones (excepting carbon metabolism); Nutrition. Photosynthesis. Respiration. Metabolism; Pigmentation - genetics; Plant physiology and development; Plant Proteins - genetics; Plants, Genetically Modified; Polymerase Chain Reaction; Promoter Regions, Genetic; Proto-Oncogene Proteins c-myb; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Plant - genetics; RNA, Plant - metabolism; Sequence Homology, Amino Acid; Species Specificity; Storage and secretion, pigments, phytochrome; Transformation, Genetic; Zea mays - genetics; Zea mays - metabolism; Monocotyledones; Petunia hybrida; Homology; Activation; Dihydrokaempferol 4-reductase; Cereal crop; Gene; Gramineae; Dicotyledones; Angiospermae; Pigments; Solanaceae; Sequencing; Anthocyanin; Helix loop helix structure; Zea mays; Enzyme; Tissue specificity; Gene expression; Metabolism; Protein; Molecular evolution; Flower crop; Isolation; Spermatophyta; Oxidoreductases; Biological accumulation
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1998.00046.x

The regulatory anthocyanin loci, an1, an2, an4 and an11 of Petunia hybrida, and r and c1 from Zea mays, control transcription of different sets of target genes. Both an2 and c1 encode a MYB-type protein. This study reports the isolation of a P. hybrida gene, jaf13, encoding a basic helix-loop-helix protein that, on the basis of sequence homology and intron/exon structure, represents the P. hybrida orthologue of the Z. mays r genes. Ectopic expression of an2 and jaf13 is sufficient for activation of the dihydroflavonol 4-reductase-A (dfrA) promoter and enhanced pigment accumulation in P. hybrida. This indicates that an2 and jaf13 play a key role in determining the tissue-specific expression pattern of structural genes. However, because chalcone synthase (chs) and flavanone-3-hydroxylase (f3h) are not activated, the pattern of pigmentation is not fundamentally altered. Expression of an2 in Z. mays complements a mutation in pl, a c1 paralogue, indicating that an2 activates a wider set of target genes in this host. Transient expression assays in Z. mays and P. hybrida tissues showed that C1 and R or AN2 and JAF13 can activate the promoter of the c2 gene, encoding Z. mays CHS, but not the chsA promoter from P. hybrida. These results indicate that regulatory anthocyanin genes are conserved between species and that divergent evolution of the target gene promoters is responsible for the species-specific differences in regulatory networks.