The PrFRS2-PrMYB75a module regulates petal coloration in flare tree peony (Paeonia rockii)

Abstract

Flower color is an essential biological and ornamental trait in plants. Paeonia rockii (flare tree peony, FTP) exhibits diverse flower colors, characterized by a distinctive basal flare in petals, which enhances its ornamental and ecological value. However, while previous research has mainly focused on flare formation, the regulatory mechanisms controlling the background color of petals remain unclear. This study identifies a novel regulatory module governing petal background coloration in FTP. Within this module, PrMYB75a acts as the central regulator to promote anthocyanin accumulation, as evidenced by stable transformation in Arabidopsis thaliana and tobacco (Nicotiana tabacum), as well as virus-induced gene silencing in FTP. Furthermore, yeast one-hybrid, dual-luciferase reporter, and electrophoretic mobility shift assays collectively demonstrated that PrMYB75a directly activates two key anthocyanin structural genes, PrCHS1 and PrANS, by interacting with MYB-binding sites nearest to the ATG start codon in their promoters. Additionally, we identified an upstream regulator, PrFRS2, which activates both PrMYB75a and PrANS by binding to the FAR1/FHY3-binding sites in their promoters. Modulation of PrFRS2 expression levels through gene silencing and overexpression resulted in alterations in flower pigmentation in both FTP and tobacco. In summary, within the PrFRS2-PrMYB75a module, PrFRS2 indirectly activates PrCHS1 and PrANS by regulating PrMYB75a, or directly activates PrANS, leading to anthocyanin accumulation in FTP purple petals. This module represents a novel regulatory mechanism of petal background coloration in FTP, providing new perspectives on color variation in flowering plants and offering genetic resources for the improvement of the flower color trait in tree peonies.

Acknowledgements

The work was supported by the National Key Research and Development Program of China (2023YFD1200105), the National Natural Science Foundation of China (31972446), and the 5·5 Engineering Research & Innovation Team Project of Beijing Forestry University, China (BLRC2023A06). We also thank Dr. P. Yan (Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences) for providing the pNC-line vectors, Dr. Rui Wang (Beijing Academy of Agriculture and Forestry Sciences) for the guidance on protein experiments, and Y. Du (Analysis Center, Tsinghua University) for her assistance with Confocal LSM imaging.

Authors contributions

F.-Y.C. planned and designed the research. F.-T.Q. and J.-N.H. conducted the experiments and performed the data analyses. F.-T.Q. wrote the manuscript. J.-N.H. and F.-Y.C. revised the manuscript. Y.Z., L.Z., Y.-F.Z., and X.-F.L. performed part of the data analysis and material preparation. All authors have read and approved the manuscript.

Data availability

The transcriptome databases used in this study are available at the China National Gene Bank under accession number PRJCA030598.

Conflicts of interest statement

The authors declare that they have no conflict of interest.

Supplementary material

Supplementary material is available at Horticulture Research online.

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