Molecular Cloning and Functional Analysis of Three FLOWERING LOCUS T (FT) Homologous Genes from Chinese Cymbidium

The FLOWERING LOCUS T (FT) gene plays crucial roles in regulating the transition from the vegetative to reproductive phase. To understand the molecular mechanism of reproduction, three homologous FT genes were isolated and characterized from Cymbidium sinense "Qi Jian Bai Mo", Cymbidium goeringii and Cymbidium ensifolium "Jin Si Ma Wei". The three genes contained 618-bp nucleotides with a 531-bp open reading frame (ORF) of encoding 176 amino acids (AAs). Alignment of the AA sequences revealed that CsFT, CgFT and CeFT contain a conserved domain, which is characteristic of the PEBP-RKIP superfamily, and which share high identity with FT of other plants in GenBank: 94% with OnFT from Oncidium Gower Ramsey, 79% with Hd3a from Oryza sativa, and 74% with FT from Arabidopsis thaliana. qRT-PCR analysis showed a diurnal expression pattern of CsFT, CgFT and CeFT following both long day (LD, 16-h light/8-h dark) and short day (SD, 8-h light/16-h dark) treatment. While the transcripts of both CsFT and CeFT under LD were significantly higher than under SD, those of CgFT were higher under SD. Ectopic expression of CgFT in transgenic Arabidopsis plants resulted in early flowering compared to wild-type plants and significant up-regulation of APETALA1 (AP1) expression. Our data indicates that CgFT is a putative phosphatidylethanolamine-binding protein gene in Cymbidium that may regulate the vegetative to reproductive transition in flowers, similar to its Arabidopsis ortholog.