CmFTL2 is involved in the photoperiod- and sucrose-mediated control of flowering time in chrysanthemum

The chrysanthemum genome harbors three FT-like genes: CmFTL1 and CmFTL3 are thought to act as regulators of floral induction under long-day (LD) and short-day (SD) conditions, respectively, whereas the function of CmFTL2 is currently unclear. The objective of the present research was to explore the function of CmFTL2 in the determination of flowering time of the photo-insensitive chrysanthemum cultivar ‘Floral Yuuka’, both in response to variation in the photoperiod and to the exogenous provision of sucrose. Spraying leaves of ‘Floral Yuuka’ plants with 50 mM sucrose accelerated flowering and increased the level of CmFTL2 transcription in the leaf more strongly than either CmFTL1 or FTL3 under both long and SD conditions. Transcription profiling indicated that all three CmFTL genes were upregulated during floral induction. The relationship of the CmFTL2 sequence with that of other members of the PEBP family suggested that its product contributes to the florigen rather than to the anti-florigen complex. The heterologous expression of CmFTL2 in the Arabidopsis thaliana ft-10 mutant rescued the mutant phenotype, showing that CmFTL2 could compensate for the absence of FT. These results suggest that CmFTL2 acts as a regulator of floral transition and responds to both the photoperiod and sucrose.