GA 2-oxidase( GA2ox) is a critical enzyme in the pathway of gibberellins biosynthesis. In this research ,GA2ox gene was isolated from Fuji stem apical tissue by homologous cloning technology. The cDNA sequence of GA2ox was 1 656 bp in length with 3 exons and 2 introns. Its open reading frame was 1 014 bp which encoding a protein of 337 amino acids. Molecular weight and isoelectric point of the protein was 37. 679 8 kDa and 6. 41, respectively. Conserved domains showed that the enzyme belonged to the class 2-oxoglutarate-dependent dioxygenas-es. Amino acids homology analysis indicated that the sequence had 51% -97% similarity with those of other reported plants. Cluster analysis showed that GA2ox from pear was clustered together with GA2ox from apple firstly,and followed by that from black cottonwood.%GA2ox是赤霉素合成代谢的关键酶,以苹果品种富士茎尖为供试材料,应用同源克隆技术克隆GA2ox基因,获得长度为1656 bp的DNA序列和1014 bp cDNA序列.对比分析表明,DNA序列存在3个外显子和2个内含子.GA2ox的开放性阅读框编码337个氨基酸残基,推断其相对分子量为37.6798 kDa,等电点为6.41.蛋白质结构域检索表明,GA2ox属于依赖于2-酮戊二酸的双加氧酶家族成员；氨基酸同源性分析表明,GA2ox与已报道的其他植物的GA2ox氨基酸序列同源性为51％ ～97％；氨基酸聚类分析表明,苹果和梨首先聚类,其次是毛果杨.
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