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

Abstract

Summary 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.

Effects of Salt Stress after Late Booting Stage on Yield and Antioxidant Capacity in Pigmented Rice Grains and Alleviation of the Salt-Induced Yield Reduction by Exogenous Spermidine

“…On the contrary, the red rice had higher proanthocyanidin contents. Min et al (2012) reported higher proanthocyanin content in red rice, and Furukawa et al (2006) reported higher anthocyanin contents in black or purple rice. The anthocyanin and proanthocyanidin synthesis pathways share dihydroflavonols as precursor molecules.…”

bHLH05 Is an Interaction Partner of MYB51 and a Novel Regulator of Glucosinolate Biosynthesis in Arabidopsis

“…Furthermore, the MYB-bHLH protein complexes involved in the regulation of flavonoid genes in Arabidopsis and also in other species such as rice (Oryza sativa), maize (Zea mays), cotton (Gossypium hirsutum), apple (Malus domestica), strawberry (Fragaria spp. ), snapdragon (Antirrhinum majus), beefsteakplant (P. frutescens), gerbera (Gerbera hybrida), and clustered gentian (Gentiana triflora; Martin et al, 1991;Grotewold et al, 2000;Hu et al, 2000;Aharoni et al, 2001;Sompornpailin et al, 2002;Elomaa et al, 2003;Humphries et al, 2005;Schwinn et al, 2006;Sweeney et al, 2006;Espley et al, 2007;Furukawa et al, 2007;Nakatsuka et al, 2008;Brueggemann et al, 2010;LinWang et al, 2010) have been rigorously characterized.…”

The Birth of a Black Rice Gene and Its Local Spread by Introgression

“…The red grain color is ubiquitous in wild rice (Oryza rufipogon) varieties, which share common ancestors with cultivated rice, and the defect in Rc was spread broadly into most rice varieties in the process of domestication (Sweeney et al, 2007). To date, only two loci for the red rice trait have been reported; Rc, which encodes a bHLH transcription factor, and Rd, which encodes dihydroflavonol-4-reductase (DFR) (Sweeney et al, 2006;Furukawa et al, 2007). The black (or purple) grain color has not been observed in any accessions of O. rufipogon (see Oryzabase, http://www.gramene.org/).…”