Two-Gene Switch Turns Flare Tree Peony Purple: Unlocking the Secrets of Petal Color
Flower color is a captivating feature in ornamental plants, but the genetic mechanisms behind subtle background pigmentation have remained elusive. In the case of flare tree peony (Paeonia rockii), previous research has primarily focused on the dramatic basal flare, leaving the regulation of uniform petal background color in the shadows. Now, a groundbreaking study has shed light on a novel transcriptional module, PrFRS2–PrMYB75a, which governs the purple background coloration in these exquisite flowers.
Anthocyanins, the pigments responsible for red, purple, and blue hues in most flowering plants, play a crucial role in the vibrant colors of tree peonies. The study reveals that the MYB transcription factor PrMYB75a directly activates key anthocyanin biosynthetic genes, while the upstream regulator PrFRS2 enhances pigment accumulation both indirectly through PrMYB75a and directly by targeting structural genes. This intricate regulatory hierarchy orchestrates anthocyanin accumulation and shapes the petal coloration patterns.
The research team, led by scientists from Beijing Forestry University, made a fascinating discovery by comparing purple and white cultivars of Paeonia rockii. They identified the key MYB transcription factor PrMYB75a and its upstream regulator PrFRS2, which work in tandem to control anthocyanin accumulation. Through a series of experiments, including transcriptome analysis, transgenic validation, gene silencing, and molecular interaction assays, the researchers unveiled the hierarchical regulatory mechanism that determines whether petals develop a purple background.
To delve deeper into the determinants of background coloration, the researchers compared two cultivars: the purple 'Jing Hong' and the white 'Jing Yu Dan'. Biochemical analyses revealed that purple petals accumulate cyanidin, peonidin, and pelargonidin derivatives, while white petals contain negligible anthocyanins. Peonidin 3,5-di-O-glucoside was identified as the predominant pigment. Transcriptome comparisons showed that 14 anthocyanin pathway-related genes were significantly upregulated in purple petals, with PrMYB75a exhibiting an astonishing 100-fold higher expression at the onset of pigmentation.
The study's findings have profound implications for flower color modification in tree peony breeding programs. By manipulating the expression of PrMYB75a and PrFRS2, breeders can achieve stable and predictable changes in petal background coloration. Moreover, the FRS-family transcription factors' responsiveness to environmental cues like light and temperature suggests that this module could link environmental signals to pigment accumulation, offering strategies to maintain ornamental quality in various growing conditions.
This discovery not only enhances our understanding of anthocyanin regulatory networks in ornamental plants but also contributes to the broader field of hierarchical transcriptional regulation, floral pattern diversification, and precision breeding in ornamental and horticultural crops. The PrFRS2–PrMYB75a module represents a precise molecular target for improving flower color traits, opening up exciting possibilities for the future of tree peony breeding and beyond.
