AtTHIC, a gene involved in thiamine biosynthesis in Arabidopsis thaliana
AtTHIC, a gene involved in thiamine biosynthesis in Arabidopsis thaliana
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DOI：
10.1038/cr.2008.35
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发表时间：
2008-05-01
期刊：
影响因子：
44.1
通讯作者：
Ling, Hong-Qing
中科院分区：
文献类型：
--
作者：
Kong, Danyu;Zhu, Yuxing;Ling, Hong-Qing
硫胺素（维生素B-1）是生物体必需的化合物。它含有一个嘧啶环结构和一个噻唑环结构。硫胺素的这两个部分独立合成，然后偶联在一起。在这里，我们报告的AtTHIC，这是参与在拟南芥硫胺素生物合成的分子特征。AtTHIC类似于大肠杆菌ThiC，其参与原核生物中的嘧啶生物合成。AtTHIC的异源表达可以在功能上补充大肠杆菌thiC敲除突变体。杆菌通过在AtTHIC启动子区插入T-DNA下调AtTHIC的表达导致植物中硫胺素含量的急剧降低，敲低突变体thic 1在正常培养条件下表现出白化病（白色叶片）和致死表型。thic 1突变体可以通过补充硫胺素来挽救，并且其缺陷功能可以通过AtTHIC cDNA的表达来补充。瞬时表达分析显示AtTHIC蛋白靶向质体和叶绿体。AtTHIC在叶、花和角果中强烈表达，外源硫胺素下调AtTHIC的转录。总之，AtTHIC是拟南芥硫胺素生物合成途径中参与嘧啶合成的基因，我们的研究结果为阐明植物硫胺素生物合成途径提供了一些新的线索。
Thiamine (vitamin B-1) is an essential compound for organisms. It contains a pyrimidine ring structure and a thiazole ring structure. These two moieties of thiamine are synthesized independently and then coupled together. Here we report the molecular characterization of AtTHIC, which is involved in thiamine biosynthesis in Arabidopsis. AtTHIC is similar to Escherichia coli ThiC, which is involved in pyrimidine biosynthesis in prokaryotes. Heterologous expression of AtTHIC could functionally complement the thiC knock-out mutant of E. coli. Downregulation of AtTHIC expression by T-DNA insertion at its promoter region resulted in a drastic reduction of thiamine content in plants and the knock-down mutant thic1 showed albino (white leaves) and lethal phenotypes under the normal culture conditions. The thic1 mutant could be rescued by supplementation of thiamine and its defect functions could be complemented by expression of AtTHIC cDNA. Transient expression analysis revealed that the AtTHIC protein targets plastids and chloroplasts. AtTHIC was strongly expressed in leaves, flowers and siliques and the transcription of AtTHIC was downregulated by extrinsic thiamine. In conclusion, AtTHIC is a gene involved in pyrimidine synthesis in the thiamine biosynthesis pathway of Arabidopsis, and our results provide some new clues for elucidating the pathway of thiamine biosynthesis in plants.