Abstract:

Cryptochrome 2（CRY2）was isolated from Paeonia suffruticosa by RT-PCR. The full open
reading fragment（ORF）length of PsCRY2 encoding 633 amino acids was 1 902 bp，and the GenBank No.
was KP982893. Sequence alignment and motif analysis showed that the deduced amino acids contained a
PHR domain near the amino terminus and a CCT domain near the carboxy terminus. It was designated as
PsCRY2，according to its high identity with AtCRY2 in Arabidopsis. Phylogenetic analysis showed that it
had close relationship with Citrus sinensis. Gene expression analysis revealed that the highest expression
levels of PsCRY2 were appeared in the bud and seed embryo of P. suffruticosa，followed by root，stem and
leaves. The expression of PsCRY2 in the whole process of bud differentiation was high. While the
expression of PsCRY2 was low in the early stage of bud development and quite high in the middle and latestage. The expression of PsCRY2 reached a peak in big bell-like flower-bud. The results suggested that
PsCRY2 play an important role both in the process of bud differentiation and bud development. The
expression patterns of PsCRY2 in the bud of‘Luoyanghong’and‘Qiufa 1’were similar，while the
expression level of PsCRY2 in the bud of‘Qiufa 1’was significantly higher than that in the bud of
‘Luoyanghong’. The expression patterns of PsCRY2 in the buds with different photoperiod treatments
were different. The expression of PsCRY2 decreased in bud sprouting and small bell-like flower bud under
short day photoperiod，compared with that in long day photoperiod.

Key words: tree peony, photoperiod pathway, cryptochromes, PsCRY2, qRT-PCR