Tree peony is prized for its large blossoms, yet its flowering depends heavily on proper bud dormancy release after winter chilling. However, climate warming has reduced chilling accumulation in many regions, leading to incomplete dormancy release, reduced budburst, and poorer flowering performance. Gibberellin (GA) signaling is known to participate in breaking dormancy, where DELLA proteins act as negative regulators. Meanwhile, MADS-box transcription factors play central roles in developmental transitions, including flowering and dormancy cycles. Yet, the molecular connection linking GA signaling, MADS-box factors, and bud cell reactivation remains unclear. Due to these challenges, it is necessary to conduct further research on the regulatory mechanisms driving tree peony dormancy release.
Researchers from Qingdao Agricultural University report that the MADS-domain transcription factor PsAGL9 acts as an essential regulator of bud dormancy release in tree peony. The study, published (DOI: 10.1093/hr/uhaf043) on May 1, 2025, in Horticulture Research, reveals that PsAGL9 interacts with the DELLA protein PsRGL1 within the GA pathway. Upon chilling-induced degradation of PsRGL1, PsAGL9 activates cell-cycle and bud-break-associated genes, including PsCYCD and PsEBB3, thereby promoting dormancy release. The work uncovers a GA-responsive regulatory module with direct relevance to flowering timing and plant adaptation.
The team first identified PsAGL9 as a protein that physically interacts with PsRGL1, a DELLA protein previously shown to inhibit dormancy release. Expression analyses revealed that PsAGL9 was strongly induced by both low-temperature exposure and exogenous GA treatment, aligning with the dormancy release process. Overexpressing PsAGL9 in chilled buds accelerated budbreak and led to earlier activation of several well-known dormancy-release marker genes, including PsCYCD, PsEBB1, PsEBB3, PsBG6, and PsBG9.
Promoter binding assays demonstrated that PsAGL9 directly binds to CArG motifs in the promoters of PsCYCD and PsEBB3, genes involved in restarting the cell cycle and triggering bud growth. Furthermore, the interaction with PsRGL1 was shown to restrain PsAGL9 activity, preventing it from binding DNA until PsRGL1 levels decline during prolonged chilling and GA accumulation. The study also identified additional MADS-box partners, PsAGL6 and PsPI, which form heterodimers with PsAGL9 and further enhance its transcriptional activation of downstream genes. Together, these findings establish a GA-dependent regulatory module: GA → degradation of PsRGL1 → release of PsAGL9 dimers → activation of PsCYCD and PsEBB3 → bud dormancy release.
“Our findings reveal a missing molecular link in how GA signaling activates bud growth after winter dormancy,” said the study's corresponding authors. “The transcription factor PsAGL9 acts as a molecular switch that shifts the bud from a dormant state to active cell division. This mechanism not only explains how tree peonies coordinate seasonal growth transitions but also provides a framework for understanding dormancy regulation in other perennial species.”
This regulatory pathway provides a promising genetic target for improving flowering reliability in tree peony under warming climates. By modulating PsAGL9, breeders may be able to reduce the plant's chilling requirement or stabilize flowering timing across variable winters. The findings also expand fundamental understanding of perennial dormancy control, offering conceptual insight relevant to fruit trees, ornamentals, and forest crops. Future applications could include molecular breeding, hormone-tuning cultivation strategies, and the development of dormancy-release treatments to support horticultural production in regions experiencing climate-related winter warming.
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References
DOI
10.1093/hr/uhaf043
Original Source URL
https://doi.org/10.1093/hr/uhaf043
Funding information
This work was supported by grants from National Natural Science Foundation of China (32371938, 32271941, 32471957, 32201597), the Agricultural Seed Engineering Project of Shandong Province (2020LZGC011-1-4).
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.