Journal Article

The C–S–A gene system regulates hull pigmentation and reveals evolution of anthocyanin biosynthesis pathway in rice

Xingming Sun, Zhanying Zhang, Chao Chen, Wei Wu, Nannan Ren, Conghui Jiang, Jianping Yu, Yan Zhao, Xiaoming Zheng, Qingwen Yang, Hongliang Zhang, Jinjie Li and Zichao Li

in Journal of Experimental Botany

Volume 69, issue 7, pages 1485-1498
Published in print March 2018 | ISSN: 0022-0957
Published online January 2018 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/ery001
The C–S–A gene system regulates hull pigmentation and reveals evolution of anthocyanin biosynthesis pathway in rice

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Abstract

Floral organs in rice (Oryza sativa) can be purple, brown, or red in color due to the accumulation of flavonoids, but the molecular mechanism underlying specific organ pigmentation is not clear. Here, we propose a C–S–A gene model for rice hull pigmentation and characterize it through genetic, molecular, and metabolomic approaches. Furthermore, we conducted phylogenetic studies to reveal the evolution of rice color. In this gene system, C1 encodes a R2R3-MYB transcription factor and acts as a color-producing gene, and S1 encodes a bHLH protein that functions in a tissue-specific manner. C1 interacts with S1 and activates expression of A1, which encodes a dihydroflavonol reductase. As a consequence, the hull is purple where functional A1 participation leads to high accumulation of cyanidin 3-O-glucoside. Loss of function of A1 leads to a brown hull color due to accumulation of flavonoids such as hesperetin 5-O-glucoside, rutin, and delphinidin 3-O-rutinoside. This shows a different evolutionary pathway of rice color in japonica and indica, supporting independent origin of cultivars in each subspecies. Our findings provide a complete perspective on the gene regulation network of rice color formation and supply the theoretical basis for extended application of this beneficial trait.

Keywords: Color; domestication; evolution; flavonoid; gene interaction; gene network; rice

Journal Article.  9494 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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