Department of Applied Bioscience and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane, 690-8504 Japan.
Plant Cell Physiol. 2012 Mar;53(3):592-601. doi: 10.1093/pcp/pcs014. Epub 2012 Feb 9.
Unraveling the role of genes annotated as protein of unknown function is of importance in progression of plant science. l-Galactono-1,4-lactone (l-GalL) is the terminal precursor for ascorbic acid (AsA) biosynthesis in Arabidopsis thaliana, and a previous study showed two DUF (domains of unknown function) 642 family genes (At1g80240 and At5g25460, designated as DGR1 and DGR2, respectively) to be sensitive to it. In this work, leaves from wild-type Arabidopsis were fed with d-glucose, l-galactose, l-GalL and AsA, and the expression level of the At1g80240 and At5g25460 genes showed a specific response to l-GalL, but not to the other supplements despite the increases of the tissue AsA contents. Analysis of promoter-β-glucuronidase (GUS) transgenic plants showed the two genes to be complementarily expressed at the root apex and in the rest of the root excluding the apex, respectively, in both young and old seedlings, and to be expressed at the leaf primordia. The GUS activity under the control of the At5g25460 promoter was high in the cotyledon and leaf veins of young seedlings. These findings were consistent with the results of quantitative real-time PCR. Interestingly, the T-DNA insertion mutant of At5g25460 (SALK_125079) displayed shorter roots and smaller rosettes than Col-0; however, no phenotypic difference was observed between the T-DNA insertion mutant of At1g80240 and the wild type. This is the first report on the expression and functional analysis of these two DUF642 family genes, with the results revealing the contribution of DGR genes to the development of Arabidopsis.
解析未知功能蛋白基因在植物科学进展中的作用至关重要。l-半乳糖酸-1,4-内酯（l-GalL）是拟南芥中抗坏血酸（AsA）生物合成的末端前体，先前的研究表明，两个结构域未知功能（DUF）642 家族基因（At1g80240 和 At5g25460，分别命名为 DGR1 和 DGR2）对其敏感。在这项工作中，用 d-葡萄糖、l-半乳糖、l-GalL 和 AsA 饲喂野生型拟南芥叶片，At1g80240 和 At5g25460 基因的表达水平对 l-GalL 表现出特异性反应，但对其他补充剂没有反应，尽管组织 AsA 含量增加。启动子-β-葡萄糖醛酸酶（GUS）转基因植物分析表明，这两个基因在根尖和根尖以外的根的其余部分分别互补表达，在幼叶和老叶中均有表达。在幼叶中，At5g25460 启动子控制下的 GUS 活性在子叶和叶脉中较高。这些发现与定量实时 PCR 的结果一致。有趣的是，At5g25460 的 T-DNA 插入突变体（SALK_125079）比 Col-0 的根短且莲座叶小；然而，At1g80240 的 T-DNA 插入突变体与野生型之间没有观察到表型差异。这是首次对这两个 DUF642 家族基因进行表达和功能分析的报道，结果表明 DGR 基因对抗生素的发育有贡献。
