Abstract: AtVTC1 is one of the key enzymes of L-galactose pathway in Arabidopsis thaliana, which is the primary vitamin C (Vc) biosynthesis pathway. It has been reported that AtVTC1 can be regulated both in transcriptional and post-transcriptional levels. This study found that there was an intron in the 5′UTR (5′untranslated region) of AtVTC1, and this 5′UTR ligated with different truncations of upstream promoter to promote high level expression of GUS, by detecting GUS activity in transgenic seedlings. The GUS expression was significantly reduced under the AtVTC1 promoter with the deletion of 5′UTR intron. However, the intron itself could not be able to activate the GUS expression. Generally the introns function as enhancers with specific nucleotide sequences, such as GATCTG motif, which was dispersed throughout the 5′UTR intron of AtVTC1. Some homologous genes of VTC1 in Arabidopsis and rice also have 5′UTR intron. These results suggested that the 5′UTR intron of AtVTC1 function would be as an enhancer in Arabidopsis, which would lay a foundation for further studies on the modulation of Vc biosynthesis on the transcription level.

Key words: Arabidopsis, AtVTC1, 5′UTR, intron, enhancer

摘要： 拟南芥VTC1(AtVTC1)是维生素C(Vc)的主要合成途径—L-半乳糖途径的关键酶之一，AtVTC1在转录水平和转录后水平均受到调控。通过生物信息学分析发现AtVTC1的5’UTR(5’untranslated regions, 5’非翻译区）中包含一个内含子，将5’UTR和启动子不同删除片段与报告基因GUS融合，通过检测转基因拟南芥的GUS活性发现这些片段均能启动GUS的高度表达；然而，将5’UTR中的内含子删除后，GUS的表达明显降低，但5’UTR自身并不能启动GUS的表达。序列分析发现，AtVTC1的5’UTR内含子包含有多个增强其功能的特征序列，如GATCTG基序。同时，AtVTC1在拟南芥和水稻的同源基因中同样具有5’UTR内含子。以上结果表明，AtVTC1的5’UTR内含子可能具有增强子的功能，分析保守的5’UTR内含子功能为进一步探究在转录水平上的Vc合成调控机制奠定基础。

关键词: 拟南芥；AtVTC1；5&rsquo, UTR；内含子；增强子