Researchers at Beijing Forestry University have identified a genetic mechanism controlling the subtle purple background coloration in flare tree peony petals (Paeonia rockii), a trait distinct from the more studied dark basal flare. The discovery, published in Horticulture Research, centers on a two-gene regulatory module, PrFRS2–PrMYB75a, which governs anthocyanin accumulation and petal coloration patterns.
Although previous studies focused on the dramatic basal flare of the peony, the genetic basis for the uniform background color remained largely unknown. The team’s research compared purple ‘Jing Hong’ and white ‘Jing Yu Dan’ cultivars, revealing significant differences in anthocyanin levels. Purple petals accumulated cyanidin, peonidin, and pelargonidin derivatives, while white petals contained negligible anthocyanins, with peonidin 3,5-di-O-glucoside being the predominant pigment in the purple variety.
Transcriptome analysis revealed that 14 anthocyanin pathway-related genes were significantly upregulated in the purple petals. Notably, the R2R3-MYB transcription factor PrMYB75a exhibited over 100-fold higher expression at the onset of pigmentation. Researchers confirmed PrMYB75a’s role through genetic experiments. Overexpression of the gene in Arabidopsis thaliana and Nicotiana tabacum resulted in increased anthocyanin accumulation and intensified pigmentation. Conversely, silencing the gene in peony petals reduced anthocyanin levels by more than 80 percent.
Further investigation revealed that PrMYB75a directly activates key anthocyanin biosynthetic genes, specifically PrCHS1 and PrANS, by binding to their promoters. The research team then identified PrFRS2, a FAR1-related transcription factor, as an upstream regulator of PrMYB75a. PrFRS2 activates PrMYB75a expression by binding to its promoter, and likewise directly activates PrANS, establishing a dual regulatory pathway that amplifies anthocyanin biosynthesis.
“Our study reveals a previously uncharacterized regulatory module controlling petal background coloration in Paeonia rockii,” stated the corresponding author. “Unlike basal flare formation, which depends on spatially restricted MYB expression, uniform background coloration is governed by coordinated activation of anthocyanin genes through PrFRS2 and PrMYB75a. This hierarchical control mechanism highlights how transcription factors integrate regulatory signals to shape floral pigmentation.”
The identification of the PrFRS2–PrMYB75a module offers potential molecular targets for breeders seeking to improve flower color traits in tree peonies. Manipulating the expression of these transcription factors could lead to stable and predictable modifications in petal background coloration. Because FRS-family transcription factors are often responsive to environmental cues like light and temperature, the module may also link environmental signals to pigment accumulation, potentially offering strategies to maintain ornamental quality under varying growing conditions. The findings also contribute to a broader understanding of transcriptional regulation and floral pattern diversification in ornamental and horticultural crops.
