Allelic Gene Interaction and Anthocyanin Biosynthesis of Purple Pericarp Trait for Yield Improvement in Black Rice

Abstract

Rice (Oryza sativa L.) is one of the major cereal crops for consumption by the world's population. Recently, various colored rice, such as white, red, brown, green, and black rice, have caught the attention of world consumers. The commercial name 'black rice' contains a high amount of anthocyanins in pericarp, which increases nutritional value. Moreover, anthocyanin in black rice possesses biomedical properties, including anti-oxidant, anti-cancer, and anti-inflammatory effects in humans. In genetics, black rice has a dominant PURPLE PERICARP (Prp) trait governed by two genes, Pb and Pp, which are involved in the synthesis of cyanidin-3-O-glucoside (C3G). Since the publication of a report by Nagai at 1921, the genetics and physiological studies of black rice driven by Prp traits are still unable to understand the relevant genes and their roles. However, with the increased demand for anthocyanin-rich black rice as a functional food for human health, it has become urgent to develop highyielding anthocyanin-rich varieties of rice. We explored many years in the genetics of purple pericarp trait, anthocyanin biosynthesis in pericarp during seed development, and, consequently, their products in relation to different physiological and agronomic traits. In this review, we summarized the anthocyanin biosynthesis in pericarp, emphasizing the inheritance pattern of the trait and functions of their products on different physiological and agronomic traits, including the yield of black rice.

Reinterpretation of anthocyanins biosynthesis in developing black rice seeds through gene expression analysis

“…We confirmed that the quantity of C3G and P3G maximally accumulated in the seeds of Heuknam and Heukseol, black rice cultivars, at around 20 DAH (Lee et al, unpublished), which corresponds to a previous report [57], and collected developing seeds of Dongjin, Geonganghongmi, Jeokjinju, Boseokheukchal, Heukjinju, Heukjinmi, and Heukseol at 20 DAH for gene expression analysis. To check the overall expression patterns of genes putatively involved in the biosynthetic pathway of anthocyanins, including bHLH [21,45], MYB [20,58], WD40 [59], PAL [22], C4H [23,24], 4CL [25], CHS [26,27], CHI [28][29][30], F3H [31,32], F3´H [36,37], DFR [33][34][35], and ANS [39][40][41], and other genes indirectly related to the biosynthetic pathway of anthocyanins, including HCT [60], CCR [61,62], CAD [63], and LAR [64], in developing seeds of white, red, and/or black rice at 20 DAH, only one replicate of total RNA samples of Dongjin, Jeokjinju, or Heukseol was chosen for RNA-seq through Illumina sequencing.…”

Determining factors, regulation system, and domestication of anthocyanin biosynthesis in rice leaves

“…The AL phenotype is common in black rice because the mutated OsB2 overlaps the function of OsRb and functional OsDFR alleles are required. However, anthocyanin accumulation in the leaf is not a favourable trait because it negatively affects yield potential (Rahman et al ., ). Rice breeders do not have an effective approach to remove the anthocyanin pigments in leaves without influencing the anthocyanin content in the pericarp because the tissue‐specific regulatory mechanism of anthocyanin biosynthesis in rice has not been characterized.…”

Developing a framework of gastronomic systems research to unravel drivers of food choice

“…The stark colour contrasts between coloured rice and viands (except for braised meats, which mostly have dark sauces, and for risotto, still a foreign concept) may also turn consumers off. However, unmilled rice is known to contain more nutrients and fibre than milled rice ( Trinidad et al, 2013 , Villareal et al, 1991 ), while dark pigments in the bran are associated with biomedical properties (reviewed in Rahman et al, 2016 ). The experts, therefore, must have included health-improving properties in defining premium rice.…”