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

Gibberellin (GA) plays a crucial role in regulating the flowering time of tree peony ( 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 GA 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 GA significantly accelerated the flower opening process. Specifically, flower buds treated with 800 mg/L and 900 mg/L GA bloomed after 42 and 45 days, respectively. In contrast, all flower buds treated with 1000 mg/L GA aborted, while only one flower bud in the control group bloomed after 56 days. Furthermore, analysis of endogenous hormone levels revealed that GA treatment rapidly increased endogenous GA levels, decreased ABA levels, and gradually increased IAA levels. Transcriptomic analysis of flower buds released from dormancy following GA 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 GA, ABA, and IAA hormone signaling pathways were also differentially expressed. Our findings suggested that an appropriate concentration of exogenous GA 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.