Abstract: On the basic of homologous sequences of Camellia japonica，a GA20-oxdiase（GA20ox）gene was isolated from the stem tip of C. reticulata‘Hentiangao’by the 3′,5′-RACE technology named CrGA20ox1（GenBank Accession ID：KP635268）. The full-length cDNA of CrGA20ox1 is 1 178 bp，containing an 1 146 bp ORF which encodes 381 amino acids. Expressions of GA20ox1 in four different plant phenotypes of camellias were analyzed by fluorescent quantitative real-time PCR. The results showed that GA20ox1 gene was expressed in the four camellias differently，where the expression level of GA20ox1 in C. chekiangoleosa was the highest，medium in C. handelii and C. nitidissima，and the lowest in C. reticulata‘Hentiangao’，which indicated that the expression intensity of the GA20ox1 gene waspositively associated with height in the different camellias. The trends of expressions of GA20ox1 gene were almost the same in various organs of the four camellias，and furthermore，the expressions of the gene was higher in the shoot tips than in tender leaves. Phenotypic results of transgenic tobacco showed that the transgenic plant with sense CrGA20ox1 gene was nearly 3.6 times height than wild type tobacco；Meanwhile，the transgenic plant with anti-sense CrGA20ox1 gene was about only half height of the wild type tobacco.

Key words: Camellia japonica, Camellia reticulata, dwarfing variety, gene clone, expression analysis, transgenic tobacco