Abstract: By screening and cloning the PsGRASs gene of peony and analyzing its expression pattern，the author preliminarily analyzed whether it participated in the dormancy release of peony，in order to provide candidate genes for anti-seasonal flower urge of peony. Based on the seed sequence of the GRAS gene family（Pfam No. PF03514），local blast was run to search GRAS gene family members in 454 sequencing transcriptomic database using the Hidden Markov Model（HMM）model and BioEdit software.As a result，two ESTs with GRAS domain were found. The full-length cDNAs were obtained by RACE. The full cDNA sequence of PsGRAS1 was 2 308 bp，the open reading frame（ORF）was 1 848 bp，encoding 615 amino acids；the PsGRAS2 was 2 034 bp，and the ORF was 1 560 bp，encoding 518 amino acids. The homology of the two PsGRAS proteins was 19.87%. The results of phylogenetic tree showed that PsGRAS1 protein and GA1，RGLs of DELLA subfamily in Arabidopsis were clustered into a large branch，PsGRAS2 protein is in a branch with Arabidopsis HAMs（AtSCL6/15/22/26/27），indicating that two GRAS members are from two different branches of the GRAS family. The tissue expression results showed that PsGRAS1 and PsGRAS2 were expressed in different tissues at the early stage of peony flowering. The expression level of PsGRAS1 was the highest in leaves and the lowest in stamens，but that of PsGRAS2 in bracts was the highest，and the lowest in the petals. PsGRAS1 genes showed a down-regulation pattern during the dormancy release，and had the lowest expression level after 28 d chilling treatment，while PsGRAS2 showed an up-regulation trend with the highest transcript level after 14 d chilling treatment and followed by a downward trend. After being treated with exogenous GA3 for 7 days，the PsGRAS1 gene showed a dramatically decreasing trend and the PsGRAS2 gene was significantly increased. These results indicated that both PsGRAS1 and PsGRAS2 were involved in the dormancy process with different functions.

Key words: tree peony, GRAS, dormancy, gibberellin, expression pattern