Buchel A S, Brederode F T, Bol J F, Linthorst H J
Institute of Molecular Plant Sciences, Gorlaeus Laboratories, Leiden University, Netherlands.
Plant Mol Biol. 1999 Jun;40(3):387-96. doi: 10.1023/a:1006144505121.
Infection of Nicotiana tabacum Samsun NN with tobacco mosaic virus (TMV) results in a hypersensitive plant response and leads to systemic acquired resistance (SAR). The induction of SAR is mediated by the plant hormone salicylic acid (SA) and is accompanied by the induced expression of a number of genes including the pathogenesis-related (PR) gene 1a. Previously, it has been found that TMV infection and SA treatment resulted in a reduction of binding of nuclear protein GT-1 to far-upstream regions (-902 to -656) of the PR-1a gene. To test if GT-1 is a negative regulator of PR-1a gene expression, the effects of mutations in the seven putative GT-1 binding sites in this region were studied in vitro using dimethyl sulfate interference footprinting and band shift assays. This showed that at least one of the seven sites is indeed a GT-1 binding site. However, when tested in transgenic plants, the mutations did not result in constitutive expression of the chimeric PR-1a/GUS transgene, while inducible expression after SA treatment was decreased. The results suggest that binding of GT-1-like proteins to far-upstream PR-1a promoter regions indeed influences gene expression. A possible model for GT-1's mode of action in PR-1a gene expression is discussed.
烟草花叶病毒（TMV）感染烟草品种三生NN会引发植物超敏反应，并导致系统获得性抗性（SAR）。SAR的诱导由植物激素水杨酸（SA）介导，并伴随着包括病程相关（PR）基因1a在内的许多基因的诱导表达。此前已发现，TMV感染和SA处理会导致核蛋白GT-1与PR-1a基因远上游区域（-902至-656）的结合减少。为了测试GT-1是否是PR-1a基因表达的负调控因子，利用硫酸二甲酯干扰足迹法和凝胶迁移试验在体外研究了该区域七个假定的GT-1结合位点突变的影响。结果表明，七个位点中至少有一个确实是GT-1结合位点。然而，在转基因植物中进行测试时，这些突变并未导致嵌合PR-1a/GUS转基因的组成型表达，而SA处理后的诱导表达却降低了。结果表明，GT-1样蛋白与PR-1a启动子远上游区域的结合确实会影响基因表达。文中讨论了GT-1在PR-1a基因表达中的可能作用模式。
