Functional Characterization of DcFT1, an Ortholog for the FLOWERING LOCUS T Gene in Carnation (Dianthus caryophyllus L.)

We analyzed FLOWERING LOCUS T (FT) orthologs to elucidate the regulatory mechanisms of flowering in carnations. There are six FT candidate genes in the carnation genome. Phylogenetic analysis and amino acid alignment suggested that four genes were FT-like genes involved in promoting flowering. Of these, Dca19666.1 had the all conserved amino acids necessary for florigen activity. Therefore, this gene was designated as DcFT1 and used for further analysis. DcFT1 transcript levels increased as the plants developed from the vegetative to the reproductive growth stages. DcFT1 was unevenly expressed in the leaves, and was more abundant in young leaves. A splice variant was identified; however, its relationship with flowering could not be determined. The early blooming cultivar showed an early elevation of DcFT1 compared to the late-blooming cultivar. Treatment to accelerate flowering by cooling at the end of the day also accelerated the increase in DcFT1 expression. The cloned DcFT1 was overexpressed in Arabidopsis for functional characterization. The resulting transgenic plants began to bolt earlier than the control plants transformed with the empty vector. qRT-PCR analysis of the DcFT1-overexpressor showed that several genes related to flowering were upregulated. These results suggest that DcFT1 is an important regulator of carnation flowering.