Unlocking the peach palette: how two genes orchestrate fruit color
image: The proposed mechanisms for jasmonates (JAs) inducible PpZAT5 and PpBBX32 modulating cultivar/temperature/tissue-dependent anthocyanin accumulation in peach fruit. The JA content in outer flesh near the peel (OF) of ‘Zhonghuashoutao’ (‘ZHST’) stored at 16°C for 15 d or 30 d and the inner flesh around the stone (IF) of ‘ZHST’ was high, while those in OF of ‘Dongxuemi’ (‘DXM’) stored at a temperature between 0°C and 16°C as well as in OF of ‘ZHST’ stored at ≤12°C was low. The high JAs level stimulated the expression of PpBBX32 and PpZAT5, with detailed mechanisms currently not revealed, and these two TFs then upregulated the expression of PpMYB10.1 by directly bound to its promoter. Moreover, these two TFs also fulfil their function by forming a protein complex in the order PpZAT5-PpBBX32-PpMYB10.1 which ultimately promoted anthocyanin accumulation in peach.
Credit: Horticulture Research
Why do some peaches turn red in the flesh, while others remain pale—even under the same conditions? Scientists have uncovered a molecular explanation involving two key transcription factors, PpBBX32 and PpZAT5, which together act as upstream switches that control the expression of PpMYB10.1, the master regulator of anthocyanin biosynthesis. These regulators respond to jasmonate hormone levels and environmental cues like temperature, orchestrating tissue-specific and cultivar-dependent pigment accumulation. The discovery sheds light on how peaches fine-tune their coloration and offers new tools for improving fruit appearance and nutritional quality.
Anthocyanins are the pigments responsible for the red, purple, and blue hues in many fruits and vegetables, contributing not only to visual appeal but also to antioxidant and health-promoting properties. In peach, anthocyanin levels vary widely across cultivars, tissues, and storage conditions. For example, moderate cold storage can trigger red coloring in the outer flesh of some peach varieties but not others. While the downstream genes involved in anthocyanin synthesis are well-known, how environmental factors and internal hormones influence their upstream regulation remains poorly understood. Due to these gaps in knowledge, there is a critical need to investigate the transcriptional networks driving these complex patterns of pigment accumulation.
A research team from Zhejiang University and the New Zealand Institute for Plant & Food Research has identified the genetic and hormonal mechanisms behind peach color variation. Their study, published (DOI: 10.1093/hr/uhae212) on July 30, 2024, in Horticulture Research, reveals how PpBBX32 and PpZAT5 regulate PpMYB10.1 expression and respond to jasmonate signaling, unlocking a clearer view of how peaches develop red hues in specific tissues and under certain temperatures.
Using transcriptomic comparisons of different peach cultivars, tissues, and storage conditions, the researchers found that anthocyanin accumulation in the outer flesh of ‘Zhonghuashoutao’ occurred only at 16°C. Two genes, PpBBX32 and PpZAT5, were identified as key regulators due to their strong expression correlation with anthocyanin levels. Functional assays confirmed that overexpressing either gene significantly boosted pigment levels in both peach and tobacco, while silencing them reduced anthocyanin accumulation. The two proteins were shown to directly bind the promoter of PpMYB10.1 and activate its transcription. Moreover, they form a ternary protein complex—PpZAT5–PpBBX32–PpMYB10.1—that further amplifies the activation of pigment-producing genes. Their expression was also inducible by methyl jasmonate, and endogenous jasmonate levels correlated with anthocyanin content across tissues and temperatures. This integrated model links environmental temperature and hormone signaling to gene regulation, explaining the precise and differential coloration observed in peach fruit.
“This study gives us a molecular explanation for something growers and consumers have observed for years—why some peaches develop beautiful red flesh while others don’t,” said Dr. Changjie Xu, corresponding author of the study. “By pinpointing PpBBX32 and PpZAT5 as central regulators responding to temperature and hormone cues, we not only expand our understanding of fruit pigmentation but also provide breeders with promising targets for enhancing both appearance and health value.”
The findings offer practical opportunities for peach breeding, postharvest storage, and even hormonal treatments to enhance fruit coloration. Targeting the PpBBX32–PpZAT5–PpMYB10.1 regulatory module may enable the development of cultivars with more vibrant and consistent red flesh across varying environments. Furthermore, postharvest treatments with jasmonate analogs or optimized storage temperatures could activate these natural genetic pathways to boost anthocyanin levels in already harvested fruit. Beyond peach, this regulatory framework may also apply to other crops where color is a key quality trait, opening doors to broader applications in horticultural science and food quality enhancement.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae212
Funding information
This work was financially supported by the National Natural Science Foundation of China (32072542), Pao Yu-Kong International Fund, Zhejiang University, and the 111 project (B17039).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.