CmGID1A-RGL1 GA-Dependent Interaction Orchestrates Flowering in Chrysanthemum

Gibberellins (GAs) are key endogenous hormones regulating chrysanthemum flowering, and Gibberellin INSENSITIVE DWARF1 (GID1) is the core receptor of the gibberellin (GA) signaling pathway. However, the functional mechanism of CmGID1A remains unelucidated. Here, we constructed CmGID1A-RNAi silencing lines and characterized the biological function of CmGID1A by phenotypic identification, protein interaction assays, qRT-PCR and RNA-seq. The results of RT-qPCR showed that CmGID1A responds to short days and gibberellins. Inhibition of the expression of CmGID1A can significantly promote the transition of chrysanthemum from the vegetative growth stage to the reproductive growth stage and accelerate its flowering process. Bimolecular fluorescence complementation (BiFC) and yeast two-hybrid (Y2H) assays confirmed that CmGID1A interacts with the DELLA protein CmRGL1 in a gibberellin-dependent manner. RNA-seq results revealed that silencing of CmGID1A leads to a significant up-regulation of downstream Ethylene Response Factor 6 (ERF6) expression. Collectively, CmGID1A acts as a GA receptor to mediate GA signal transduction via interacting with CmRGL1, and regulates the expression of CmERF6 and other downstream genes, thereby participating in the regulation of floral transition in chrysanthemum. This study clarifies the core role of CmGID1A in the GA signaling pathway and provides novel experimental data for enriching the molecular regulatory mechanism of GA in floral transition in chrysanthemum.