An R3-MYB gene of Phalaenopsis, MYBx1, represses anthocyanin accumulation
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Anthocyanins are secondary metabolites that are involved in providing flower petal pigmentation. In plants, anthocyanin synthesis is regulated positively by a conserved MYB-bHLH-WD40 (MBW) complex and negatively by repressors. We isolated a repressor of anthocyanin synthesis, MYBx1, from a moth orchid Phalaenopsis cv. Big Chili. MYBx1 encodes a typical R3-MYB protein and exhibited diverse expression patterns in four Phalaenopsis cultivars, Big Chili, Fuller’s Sunset, Sogo Yukidian “V3”, and Sogo Lit-Sunny. A yeast two-hybrid assay analysis indicated that MYBx1 can also participate in the MBW complex by interacting with the transcription factors ANTHOCYANIN (AN) 1 and AN11. Over-expressing MYBx1 in the petunia hybrid M1 × R27 resulted in reduced accumulations of flower petal pigments through the repression of anthocyanin activities. A quantitative real-time PCR analysis of the expression patterns of anthocyanin synthesis-related structural genes in the transgenic petunia flower petals showed that the expression levels of chalcone synthase, flavanone 3-hydroxylase, and dihydroflavonol reductase genes were considerably down-regulated. However, no significant changes in the expression levels of the MBW complex members, AN1, AN2, and AN11, were observed. This study improves our understanding of anthocyanin synthesis-related regulatory networks in plants and also provides an important foundation for the further genetic engineering of ornamental plant flower colors.
KeywordsAnthocyanin Gene function Phalaenopsis Transcription factor
We thank Dr. Francesca M. Quattrocchio in University of Amsterdam for the vector of pK2GW2.0/rfa (Overexpression) and petunia seeds. We thank Dr. Kai He in Lanzhou University for the vectors of pGBKT7/GW and pGADT7/GW (Y2H). We thank Lesley Benyon, PhD, from Liwen Bianji, Edanz Group China (www.liwenbianji.cn/ac), for editing the English text of a draft of this manuscript. The National Natural Science Foundation of China (Grant No. U1504320) and the Financial Project of Henan Province (2019XKYH03, 20188105) to HZ supported this study.
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Conflict of interest
The authors declare that they have no conflicts of interest.
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