Abstract: The FCA (FLOWERING CONTROL LOCAL A) gene is a conserved gene that promotes plant flowering in the autonomous pathway. The full-length cDNA sequence of FCA gene was cloned from Dendrobium officinale Kimura et Migo by siloco PCR and rapid amplification of cDNA ends technology (RACE), and named as DoFCA. Bioinformatics analysis revealed that the open reading frame of the DoFCA gene was 2301 bp, containing 19 exons and 18 introns. The DoFCA encoded a protein with 766 amino acid residues which had two RRM domains at N-terminal (131-210, 220-298) and one WW domain at C-terminal (605-634). Promoter analysis revealed that there were regulatory elements in the promoter region of this gene, which were closely related to meristem-specific activation, endosperm expression and expression regulation of anther-specific genes. Protein sequence homology analysis showed that the conserved region mainly concentrated in both the RRM and WW domain, which indicated that the protein was functionally conserved in different species. Phylogenetic analysis showed that DoFCA protein had the closest evolutionary relationship with Dendrobium-like FCA protein, and it was found that FCA protein differentiated during the evolution of monocotyledons and dicotyledons. Analysis of the DoFCA-WW/FY-PPLPP complex revealed that the four sites (14Tyr, 16Tyr, 23Ser, and 25Trp) in the WW domain interacted most closely with FY-PPLPP motif, and the 23Ser residue formed a hydrogen bond with the second Pro of FY-PPLPP motifs. The results of RT-qPCR analysis showed that the expression level of DoFCA was higher in flower, followed by stem and leaf, and the lowest in root. Under low-temperature stress, the expression level decreased rapidly after treated for 12 h, then increased gradually, and finally maintained at a high level. These results suggested that the gene might play an important role in the flower development and formation of Dendrobium officinale Kimura et Migo and also in the process of low temperature induced flowering.

Key words: RACE, Dendrobium officinale Kimura et Migo, FCA, RT-qPCR