Gibberellin promotes flowering of chrysanthemum by upregulating CmFL, a chrysanthemum FLORICAULA/LEAFY homologous gene

The plant hormone gibberellin (GA) induces flower formation in several long-day (LD) plants, and exogenous GA can partly substitute for chilling treatment in cold-dependent plants. Both chilling and GA are required to promote flowering of a short-day (SD) plant chrysanthemum as observed in many plants. Chilling and GA requirement for flowering of four cultivars were examined, and genetic variation in them was shown: those that required GA also required chilling for flowering, but those that did not require GA showed no chilling requirement. With regard to LEAFY in Arabidopsis thaliana, GA promoted the expression of CmFL, a FLORICAULA/LEAFY homologous gene from chrysanthemum, and the upregulation of CmFL required GA in cultivars with a chilling requirement. Therefore, this GA requirement can be principally attributed to the chilling requirement for flowering.