Abstract: One important flowering-regulating transcription factor gene CONSTANS（CO）was
obtained from tree peony（Paeonia suffruticosa‘Ziluolan’）by RT-PCR. The full cDNA length of PsCOL4
was 1 125 bp，and could encode 373 amino acids. Sequence alignment and motif analysis showed that the
deduced amino acids contained 2 B-box zinc figure motifs near the amino terminus and 1 conserved CCT
domain near the carboxy terminus. It was designated as PsCOL4 and the GenBank accession was
KF113358，according to its high identity of AtCOL4 in Arabidopsis. Phylogenetic analysis showed that it
has close relationship with Vitis vinifera. The results of qRT-PCR revealed that the highest expression
levels were appeared in the stems of P. suffruticosa，flowed by leaves and buds. The expression pattern of
PsCOL4 from bud swelling to big-like flower-bud showed a decreased trend. The expression of PsCOL4
has a few differences under different photoperiod treatments. The expression of PsCOL4 increase in leaves and decreased in stems under short day photoperiod，compared with that in long day photoperiod.

Key words: tree peony, photoperiod pathway, CONSTANS, PsCOL4, qRT-PCR