Rice Genomics and Genetics 2024, Vol.15, No.6, 265-276 http://cropscipublisher.com/index.php/rgg 265 Feature Review Open Access Environmental Modulation of R2R3-MYBGene Expression in Dark Purple Rice: Impacts on Anthocyanin Biosynthesis and Plant Adaptation Mengmeng Yin1,2,4, FanLuo1,2,4, Xiaoli Zhou1,2,4, Changhe Wei5, QianZhu1,2,3, JuanLi1,2,3, Lijuan Chen1,2,3 , Dongsun Lee1,2,3 1 State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, 650201, Yunnan, China 2 The Key Laboratory for Crop Production and Smart Agriculture of Yunnan Province, Yunnan Agricultural University, Kunming 650201, Yunnan, China 3 Rice Research Institute, Yunnan Agricultural University, Kunming, 650201, Yunnan, China 4 College of Agricultural Science, Xichang University, Liangshan, 615013, Sichuan, China 5 Panxi Crops Research and Utilization Key Laboratory of Sichuan Province, Xichang University, Liangshan, 615013, Sichuan, China Corresponding authors: henlijuan@hotmail.com; dongeast@naver.com Rice Genomics and Genetics, 2024, Vol.15, No.6 doi: 10.5376/rgg.2024.15.0026 Received: 22 Oct., 2024 Accepted: 26 Nov., 2024 Published: 03 Dec., 2024 Copyright © 2024 Yin et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Yin M.M., Lou F., Zhou X.L., Wei C.H., Zhu Q., Li J., Chen L.J., and Lee D.S., 2024, Environmental modulation of R2R3-MYB gene expression in dark purple rice: impacts on anthocyanin biosynthesis and plant adaptation, Rice Genomics and Genetics, 15(6): 265-276 (doi: 10.5376/rgg.2024.15.0026) Abstract The purpose of this review is to systematically summarize the impact of environmental factors on the expression of R2R3-MYB genes in dark purple rice and the subsequent effects on anthocyanin biosynthesis and plant adaptation. Many studies revealed that the expression of R2R3-MYB transcription factors (TFs), which are essential for anthocyanin biosynthesis, is markedly affected by diverse environmental factors, including light, temperature, and oxidative stress. Specifically, the OsC1 gene in rice was identified as a key regulator of anthocyanin production, which in turn enhanced the plant's tolerance to oxidative stress by reducing reactive oxygen species and improving photosynthetic efficiency. Furthermore, the paper present the intricate regulatory mechanisms of these TFs, which encompass diverse levels of control, including natural variations in gene promoters, upstream TFs, and posttranslational modifications. The findings highlight the significance of R2R3-MYB TFs in the adaptive responses of dark purple rice to environmental stresses, particularly through the modulation of anthocyanin biosynthesis. This enhanced understanding of the regulatory networks can inform future genetic modifications aimed at improving crop resilience and nutritional quality. Keywords R2R3-MYB; Anthocyanin biosynthesis; Dark purple rice; Environmental modulation; Plant adaptation; Oxidative stress; Transcription factors (TFs) 1 Introduction Anthocyanins are natural water-soluble pigments that play a crucial role in plants, providing a range of colors from red to purple and blue to various vegetative tissues and reproductive organs. In addition to attracting pollinators and seed dispersers, these pigments contribute to the plant's defense mechanisms against various environmental stresses (Upadhyaya et al., 2021; Yan et al., 2021). The biosynthesis of anthocyanins is genetically determined by structural and regulatory genes, with MYB transcription factors (TFs) occupying a dominant position within this regulatory network (Shin et al., 2016). R2R3-MYB TFs play a pivotal role in regulating the anthocyanin biosynthetic pathway (ABP) (Wu et al., 2022). These TFs interact with other proteins, including basic helix-loop-helix (bHLH) and WD-repeat proteins, to form complexes that activate or repress the expression of anthocyanin biosynthetic genes (Wang et al., 2019; Chen et al., 2021; Upadhyaya et al., 2021). For example, the R2R3-MYB protein OsC1 in rice has been demonstrated to regulate anthocyanin biosynthesis and enhance oxidative stress tolerance by modulating the expression of late ABP genes (Upadhyaya et al., 2021). Similarly, other R2R3-MYB proteins, such as TaPL1 in wheat and SsMYB1 in Chinese tallow, have been identified as positive regulators of anthocyanin biosynthesis, underscoring their significance in the regulation of this pathway (Shin et al., 2016). Dark purple or black rice, distinguished by its elevated anthocyanin concentration, represents an exemplary model for investigating the regulation of anthocyanin biosynthesis. The presence of anthocyanins in dark purple rice not only contributes to its distinctive color but also enhances its nutritional value and stress tolerance (Upadhyaya et al., 2021). The R2R3-MYB TF OsC1 has been identified as a key regulator of anthocyanin biosynthesis in dark
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