Transcriptomic Analysis of Gibberellin-Mediated Flower Opening Process in Tree Peony (Paeonia suffruticosa)

Gibberellin (GA₃) plays a crucial role in regulating the flowering time of tree peony (<i>Paeonia suffruticosa</i> Andr.). However, its function on flower opening after dormancy release remains unclear, and its molecular mechanism need further study. We investigated the effects of exogenous GA₃ treatments at 800 mg/L, 900 mg/L, and 1000 mg/L on the flowering process of five-year-old peony plants ('Luhehong') under greenhouse conditions. Our results showed that exogenous GA₃ significantly accelerated the flower opening process. Specifically, flower buds treated with 800 mg/L and 900 mg/L GA₃ bloomed after 42 and 45 days, respectively. In contrast, all flower buds treated with 1000 mg/L GA₃ aborted, while only one flower bud in the control group bloomed after 56 days. Furthermore, analysis of endogenous hormone levels revealed that GA₃ treatment rapidly increased endogenous GA₃ levels, decreased ABA levels, and gradually increased IAA levels. Transcriptomic analysis of flower buds released from dormancy following GA₃ treatment identified multiple key genes involved in the flower opening process of peony. Notably, members of the C2H2, C3H, ERF, bHLH, MYB, bZIP, NAC, and WRKY families showed significant differential expression. Moreover, several key genes involved in GA₃, ABA, and IAA hormone signaling pathways were also differentially expressed. Our findings suggested that an appropriate concentration of exogenous GA₃ treatment could accelerate the flower opening process in tree peony through multiple pathways, which would provide valuable insights into the molecular mechanisms underlying the gibberellin-mediated flower opening process in tree peony.