Abstract: In this study，we cloned a CONSTANS-like transcription factor gene that is involved in the photoperiod pathway from the Allium cepa L.‘SA2’. The full-length cDNA of the gene，designated as AcCOL7，is 1 101 bp long and encodes 366 amino acids. Sequence alignment and motif analysis show that AcCOL7 contains a B-box zinc finger motif near the amino terminus and a conserved CCT domain near the carboxy terminus. Phylogenetic analysis shows that it has close relationship with OsCOL13. Real-time quantitative PCR reveals that AcCOL7 is expressed in different tissues，with higher expression level found in tender leaf and stem before bolting. To investigate the function of AcCOL7，we constructed an AcCOL7 over-expression vector and transformed it into an Arabidopsis co mutant. We found that the transgenic plants exhibited earlier bolting and flowering compared with the mutant plants，and that other characters of the mutant plants were also recovered to some degree. These observations suggest that AcCOL7 has similar functions with the Arabidopsis AtCOL5，and that AcCOL7 likely plays a significant role in promoting flowering.

Key words: Allium cepa, AcCOL7, gene expression pattern, Arabidopsis co mutant, over-expression vector, bolting