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Article|01 Jul 2021|OPEN
The R2R3-type MYB transcription factor MdMYB90-like is responsible for the enhanced skin color of an apple bud sport mutant
Chao Sun1,2, Chunming Wang2, Wang Zhang2, Shuai Liu2, Weiyao Wang2, Xinyi Yu1, Tao Song3, Maxwell Yu4, Weichang Yu2, & Shenchun Qu1,
1College of Horticulture, Nanjing Agricultural University, No. 1 Weigang, 8210095 Nanjing, China
2Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, 518060 Shenzhen, China
3Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China
4Department of Biomedical Engineering, Washington University in St.Louis, St.Louis, MO 63130, USA

Horticulture Research 8,
Article number: 156 (2021)
doi: 10.1038/hortres.2021.156
Views: 151

Received: 24 Oct 2020
Revised: 25 Apr 2021
Accepted: 04 May 2021
Published online: 01 Jul 2021

Abstract

The anthocyanin content in apple skin determines its red coloration, as seen in a Fuji apple mutant. Comparative RNA-seq analysis was performed to determine differentially expressed genes at different fruit development stages between the wild-type and the skin color mutant. A novel R2R3-MYB transcription factor, MdMYB90-like, was uncovered as the key regulatory gene for enhanced coloration in the mutant. The expression of MdMYB90-like was 21.3 times higher in the mutant. MdMYB90-like regulates anthocyanin biosynthesis directly through the activation of anthocyanin biosynthesis genes and indirectly through the activation of other transcription factors that activate anthocyanin biosynthesis. MdMYB90-like bound to the promoters of both structural genes (MdCHS and MdUFGT) and other transcription factor genes (MdMYB1 and MdbHLH3) in the yeast one-hybrid system, electrophoretic mobility shift assay, and dual-luciferase assay. Transgenic analysis showed that MdMYB90-like was localized in the nucleus, and its overexpression induced the expression of other anthocyanin-related genes, including MdCHS, MdCHI, MdANS, MdUFGT, MdbHLH3, and MdMYB1. The mutant had reduced levels of DNA methylation in two regions (−1183 to −988 and −2018 to −1778) of the MdMYB90-like gene promoter, which might explain the enhanced expression of the gene and the increased anthocyanin content in the mutant apple skin.