Rc and Rd genes are involved in proanthocyanidin synthesis in rice pericarp

• Published in: The Plant journal : for cell and molecular biology Vol. 49; no. 1; pp. 91 - 102
• Main Authors: Furukawa, Tsutomu, Maekawa, Masahiko, Oki, Tomoyuki, Suda, Ikuo, Iida, Shigeru, Shimada, Hiroaki, Takamure, Itsuro, Kadowaki, Koh-ichi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-01-2007; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; alternative translation initiation; Amino Acid Sequence; Base Sequence; basic helix-loop-helix protein; Biological and medical sciences; Botany; Chromosome Mapping; Chromosomes, Plant; Color; dihydroflavonol-4-reductase; Economic plant physiology; Freshwater; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant; Genes, Plant - genetics; Genetic Complementation Test; Genetic Linkage; Metabolism; Metabolism. Physicochemical requirements; Molecular biology; Molecular Sequence Data; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Oryza - anatomy & histology; Oryza - genetics; Oryza - metabolism; Oryza sativa; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants, Genetically Modified; proanthocyanidins; Proanthocyanidins - biosynthesis; Protein Biosynthesis; Rice; seed color; Seeds; Seeds - metabolism; seed color; basic helix-loop-helix protein; Seeds; EC 1.1.1.219; proanthocyanidins; Gene; Transgenic plant; Mutation; rice; alternative translation initiation; dihydroflavonol-4-reductase
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2006.02958.x

Different colors, such as purple, brown, red and white, occur in the pericarp of rice. Here, two genes affecting proanthocyanidin synthesis in red- and brown-colored rice were elucidated. Genetic segregation analysis suggested that the Rd and A loci are identical, and both encode dihydroflavonol-4-reductase (DFR). The introduction of the DFR gene into an Rcrd mutant resulted in red-colored rice, which was brown in the original mutant, demonstrating that the Rd locus encodes the DFR protein. Accumulation of proanthocyanidins was observed in the transformants by the introduction of the Rd gene into the rice Rcrd line. Protein blot analysis showed that the DFR gene was translated in seeds with alternative translation initiation. A search for the Rc gene, which encodes a transacting regulatory factor, was conducted using available DNA markers and the Rice Genome Automated Annotation System program. Three candidate genes were identified and cloned from a rice RcRd line and subsequently introduced into a rice rcrd line. Brown-colored seeds were obtained from transgenic plants by the introduction of a gene containing the basic helix-loop-helix (bHLH) motif, demonstrating that the Rc gene encodes a bHLH protein. Comparison of the Rc locus among rice accessions showed that a 14-bp deletion occurred only in the rc locus.