Abstract: According to the partial sequences of potential SERK2 gene screened from suppression subtractive hybridization library，two specific primers were designed and used for 5′ and 3′ RACE amplification in this experiment. A 2 374 bp full length cDNA sequence was obtained with 158 bp 5′ untranslated region（UTR），341 bp 3′ UTR，and contained a complete ORF with 1 875 bp encoding 625 amino acids. The highest homology with PsSERK2 was VvSERK2 in Vitis vinifera with 92.95% similarity. The results of real-time PCR indicated that the highest expression level of PsSERK2 was detected in the elongating stem and the lowest in expanded leaf at the big bell-like flower-bud of tree peony，the early stage of flowering. Northern blot and fluorescence real-time PCR analysis revealed PsSERK2 was up-regulated during early chilling treatment and then declined after dormancy release. Histological observation showed that the cell division rate increased and the number of cells increased gradually during According to the partial sequences of potential SERK2 gene screened from suppression subtractive hybridization library，two specific primers were designed and used for 5′ and 3′ RACE amplification in this experiment. A 2 374 bp full length cDNA sequence was obtained with 158 bp 5′ untranslated region（UTR），341 bp 3′ UTR，and contained a complete ORF with 1 875 bp encoding 625 amino acids. The highest homology with PsSERK2 was VvSERK2 in Vitis vinifera with 92.95% similarity. The results of real-time PCR indicated that the highest expression level of PsSERK2 was detected in the elongating stem and the lowest in expanded leaf at the big bell-like flower-bud of tree peony，the early stage of flowering. Northern blot and fluorescence real-time PCR analysis revealed PsSERK2 was up-regulated during early chilling treatment and then declined after dormancy release. Histological observation showed that the cell division rate increased and the number of cells increased gradually during

Key words: Paeonia suffruticosa, PsSERK2, RACE, gene expression, division frequency