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Gibberellin 3-oxidase catalyzes the conversion of inactive gibberellin (GA) species into GAs with biological activity and it is subjected to strict developmental controls in the life cycle of a plant.In this study,33 gene sequences,encoding the gibberellin 3-oxidase (GA3ox) from Dasypyrum villosum and its dwarf mutant,were obtained.Each contained a 1 107 bp coding sequence (CDS) that encoded a putative protein containing 369 amino acids.The GA3ox protein showed 77％ to 97％ homology and shared the major conserved structural domains of GA3ox proteins with rice,sorghum bicolor,oat,barley,and wheat.Sequence alignment showed that there were 20 single nucleotide polymorphisms (SNPs) and 22 Insertion/deletions (InDels) among these sequences,which could be divided into 2 haplotypes,haplotypes Ⅰ and Ⅱ.Haplotype Ⅰ was found in the wild type and was 1 495 bp in length,and haplotype Ⅱ was found in the dwarf mutant and was 1 485 bp in length.The Q-PCR results showed that GA3ox was expressed in the leaves,roots,internodes,and stem nodes,and that there was a significant difference in the transcript level of the GA3ox between the wild type and dwarf mutant.The transcript levels of GA3ox in the leaves at the seedling stage,stem elongation stage and the heading stage,in the root and stem nodes at the stem elongation stage and in the internodes at the heading stage of the wild type,were significantly higher than those in the dwarf mutant.However,GA3ox expression in the rest of the wild type tissues at the 3 stages was slightly higher than or not different from the dwarf mutant.The results suggested that the wild type and mutant allele sequences of GA3ox in D.villosum showed 2 amino acid changes in exons and variations in the lengths of introns or the SNPs in introns,which most probably impaired the function of the enzyme,affected the GA3ox expression level,and eventually gave rise to dwarfing.