A tree peony RING-H2 finger protein, PsATL33, plays an essential role in cold-induced bud dormancy release by regulating gibberellin content.

Bud dormancy is crucial for woody perennial plants to resist low-temperature stress in winter. However, the molecular regulatory mechanisms underlying bud dormancy release are largely unclear. Here, a tree peony () transcript (), encoding a RING-H2 finger protein, was selected from previously generated RNA sequencing data of chilling-treated buds. The objective of this study is to investigate the role of PsATL33 in the regulation of cold-induced bud dormancy release. Subcellular localization assay revealed that PsATL33 was localized to the nucleus and plasma membrane. Reverse transcription-quantitative PCR analysis showed that was dramatically upregulated during cold-triggered bud dormancy release. Exogenous treatments with gibberellin (GA) increased, but abscisic acid (ABA) inhibited the transcription of . Ectopic transformation assay indicated that overexpression of in petunia promoted seed germination, plant growth, and axillary bud break. Silencing of in tree peony through virus-induced gene silencing assay delayed bud dormancy release. tobacco rattle virus (TRV)--infected buds exhibited reduced expression levels of dormancy break-related genes () and (). Silencing of decreased the accumulation of bioactive GAs, GA and GA, rather than ABA. Transcript levels of several genes involved in GA biosynthesis and signaling, including (), (), , (), and (), were changed by silencing. Taken together, our data suggest that PsATL33 functions as a positive regulator of cold-induced bud dormancy release by modulating GA production.