Abstract: We cloned a cDNA encoding GA20ox from Lilium Oriental Hybrids‘Sorbonne’using rapid amplification of cDNA ends（RACE）. The bioinformatics and expression patterns of GA20ox were analyzed in our study. Sequences analysis showed that the cloned GA20ox was 1 502 bp in length with an open reading frame（1 167 bp），which encoded 388 amino acids. The putative protein had many glycosylation，phosphorylation and N-myristoylation sites. Alignment of amino acid sequence showed that GA20ox of‘Sorbonne’shared a PLN02276 binding domain like the GA20ox in other species. Phylogenetic analysis revealed that GA20ox of‘Sorbonne’was highly homologous to GA20ox of other monocots，including Phalaenopsis equestris，Dendrobium catenatum，Phoenix dactylifera，Elaeis guineensis and Cocos nucifera. Quantitative Real-time PCR（qRT-PCR）analysis showed that GA20ox was highly expressed in stem root after germination，stem of squaring stage，leaf of germination stage and leaf expansion stage，and terminal bud of germination stage，implying the temporal and special regulation of GA20ox. The application of high GA3 concentration in germination stage had great influence on plant growth as plant height and biomass of underground were promoted by 200 mg ? L-1 and 400 mg ? L-1 of GA3 treatment，respectively. After treatment of GA3 at 200 mg ? L-1，the expression of GA20ox was significantly suppressed in all tissues（except for bulb scale）and fell to their lowest level at 12 h，especially in the stem and root with decreasing by 96.79% and 94.65% respectively. These results suggest that the expression of GA20ox may be regulated by active gibberellins with a potential feedback mechanism，thus the GA20ox may play a key role for the maintenance of endogenetic active gibberellins homeostasis in lily.

Key words: Lilium, GA20ox, gene cloning, gene expression, plant height