Three Paralogous R2R3-MYB Genes Contribute to Delphinidin-Related Anthocyanins Synthesis in Petunia hybrida
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Three Paralogous R2R3‑MYB Genes Contribute to Delphinidin‑Related Anthocyanins Synthesis in Petunia hybrida Zhenzhu Fu1 · Hui Jiang1 · Yacong Chao1,2 · Xiaoyu Dong1 · Xin Yuan1 · Limin Wang1 · Jing Zhang1 · Menglan Xu1,2 · Huijuan Wang1 · Yanmin Li1 · Jie Gao1,2 · Hechen Zhang1 Received: 21 March 2020 / Accepted: 31 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Three ANTHOCYANIN SYNTHESIS REGULATOR genes (ASR1–3) that encode R2R3-MYB transcription factors were identified recently from Petunia hybrida. In this study, we conducted additional experiments to characterize their specific function in the regulation of anthocyanin synthesis. The ASR1–3 proteins were localized in the nucleus. Analysis of their regulatory function by transient expression in the petunia corolla and yeast two-hybrid assays showed that the residues Arg at position 51 and Ala at position 102 in the N-terminal domain were essential for the regulatory function of the proteins, and the conserved domain at the C-terminal end was important for activation of the protein. RNA sequencing of overexpression (OE) and RNA-interference transgenic lines confirmed that the ASR proteins specifically induce structural genes of anthocyanin synthesis, including the early biosynthesis genes CHSj, F3H, and F3′5′H-1, the late biosynthesis genes DFR, ANS, RT, MT, AT, and GT, and the anthocyanin-related glutathione S-transferase gene AN9. In addition, a member of the detoxifying efflux carrier family, a DTX35-like gene, was upregulated by ASRs. Determination of anthocyanin/anthocyanidin contents in ASR1-OE petunia lines revealed that ASR1 especially induced the flavonoid 3′,5′-hydroxylase, which was consistent with the abundance of dihydromyricetins and delphinidins, but not cyanidins. The ASR genes were induced under high-intensity light and upregulated the expression of MYBx and MYB27, thereby providing feedback repression of anthocyanin synthesis. An updated model is presented outlining the mechanisms underlying anthocyanin synthesis in petunia. Keyword Anthocyanin · Petunia · Regulation · Transcription factor · R2R3-MYB Abbreviations AN Anthocyanin ANS Anthocyanidin synthase AT Acylation bHLH Basic helix-loop-helix 4CL 4-Coumaroyl-CoA ligase C4H Cinnamate 4-hydroxylase CHI Chalcone isomerase CHS Chalcone synthase Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00344-020-10224-y) contains supplementary material, which is available to authorized users. * Hechen Zhang [email protected] 1
Horticultural Research Institute, Henan Academy of Agricultural Sciences, Zhengzhou 450002, Henan Province, China
College of Forestry, Henan Agricultural University, Zhengzhou 450002, Henan Province, China
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DFR Dihydroflavonol 4-reductase DHK Dihydrokaempferol DHM Dihydromyricetin DHQ Dihydroquercetin DPL DEEP PURPLE F3H Flavanone 3-hydroxylase F3′H Flavonoid 3′-hydroxylase F3′5′H Flavonoid 3′,5′-hydroxylase FLS Flavonol synthase GT Glucosylation MT Methylation
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