Newswise — In perennial woody plants, bud endodormancy is crucial for survival under adverse environmental conditions in winter such as low temperature (LT) and dehydration stress. To break bud dormancy is essential for the resumption of bud growth and flowering. Tree peony (Paeonia suffruticosa Andr.) belonging to the section Moutan of the genus Paeonia and family Paeoniaceae, is famous for high ornamental and medicinal value and also known as a newly cultivated oil plant. As a perennial plant, tree peony undergoes endodormancy in late autumn. However, due to a poor understanding of the dormancy release mechanism, there are still many production problems such as flower abortion, branch shortening, and abnormal leaf and flower formation in practice, which significantly reduce commercial value and hinder the development of the tree peony industry.

Recent studies have elucidated the regulatory network of ABA and DAM (Dormancy Associated MADS-box) in modulating bud dormancy. The bioactive gibberellins (GAs) also contribute to bud dormancy release, and exogenous application of GA quickly break the bud dormancy of tree peony. However, the mechanism of GA regulating dormancy remains poorly understood.

In February 2024, Horticulture Research online published a research paper titled PsmiR159b-PsMYB65 module functions in the resumption of bud growth after endodormancy by affecting cell cycle in tree peony by Professor  Shupeng Gai of Qingdao Agricultural University.

The research explores the miR159b-GAMYB module, a classical and conservative module of GA response functioning in several physiological processes. However, its role in dormancy regulation remains unclear. In this study, PsmiR159b is highly abundance in dormant buds, and low temperature accumulation suppresses its expression in tree peony. STTM (short tandem target mimic) silencing and overexpression analysis reveals that PsmiR159b inhibites bud dormancy release (Figure 1). Genetic analysis and degradation experiment demonstrate that PsmiR159b targets to PsMYB65. PsMYB65 has the characteristics of transcription factors and plays a activation role by its TRD (transcription regulatory domain). PsMYB65 is induced by the prolonged chilling and exogenous GA3, and PsMYB65 silencing delays bud burst and presents lower relative growth rate. Transcriptomic ananlysis of PsMYB65-silenced buds identifies the differential-expressed genes are significantly enriched in the cell cycle and DNA replication pathway, among which PsCYCD3;1 is significantly down-regulated and contains a MYB-binding element on its promoter. Y1H, EMSA and dual luciferase reports assays confirm that PsMYB65 activates PsCYCD3;1 expression by binding to its promoter. Furthermore, silencing of PsCYCD3;1 inhibites cell division and delays bud burst (Figure 2). This study reveals that PsmiR159b-PsMYB65 modulates bud dormancy release by affecting cell cycle in tree peony, a novel pathway of GA regulating bud dormancy release, and  provides excellent gene resources for the molecular breeding of tree peony flowering.

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References

Authors

Tao Zhang, Xinyu Wang, Yanchao Yuan, Shoujie Zhu, Chunying Liu, Yuxi Zhang, Shupeng Gai

Affiliations

College of Life Sciences, Qingdao Agricultural University

About Shupeng Gai

Prof. Shupeng Gai, Prof. Yuxi Zhang (Co-corresponding author)

Journal Link: Horticulture Research´╝î February 2024