Molecular cloning and functional characterization of CoFT1, a homolog of FLOWERING LOCUS T (FT) from Camellia oleifera

FLOWERING LOCUS T (FT) is an important integrator of flowering genetic pathways and plays crucial roles in flowering transition. The tea-oil tree (Camellia oleifera Abel.) is a valuable woody oil crop, but the molecular mechanisms controlling flowering are still unclear. In this study, a FT-like gene, CoFT1, was isolated and characterized from C. oleifera. The CoFT1 protein was localized in the nucleus and cytoplasm of Arabidopsis protoplasts, and exhibited no transactivation activity in yeast cells. CoFT1 was highly expressed in mature leaves and reproductive organs, such as flower buds, flowers, flower organs, and young fruits. Its expression showed diurnal rhythms under both long-day and short-day conditions, and was photoperiod-dependent. Seasonal expression analysis revealed that the CoFT1 transcript in leaves increased during the floral induction period. Overexpression of CoFT1 in wild-type Arabidopsis resulted in precocious flowering and elevated the transcription levels of flowering related genes, such as SOC1, AP1, and LFY. Furthermore, the yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that CoFT1 was able to interact with both Arabidopsis FD and C. oleifera CoFD proteins. The sequence analysis revealed that the CoFT1 promoter contained a number of light-responsive elements, several hormonal- and stress-responsive motifs, and flowering related transcriptional factor binding sites, including CORE, CCAATBOX1, and CArG motifs. Our results suggested that CoFT1 might function as a flowering promoter in C. oleifera.