Beilmann A, Albrecht K, Schultze S, Wanner G, Pfitzner U M
Botanisches Institut, Ludwig-Maximilians Universität, München, FRG.
Plant Mol Biol. 1992 Jan;18(1):65-78. doi: 10.1007/BF00018457.
PR-1 genes are induced by various environmental stimuli such as pathogen attack or exposure of the plants to certain chemicals. To examine the regulation of these genes, the 5' flanking regions of the PR-la gene and of two PR-1 pseudogenes were joined by a transcriptional fusion to the Escherichia coli beta-glucuronidase (GUS) gene. These constructs were stably integrated into the tobacco genome and independent primary transformants were monitored for the expression of the reporter gene. Unexpectedly, out of 55 transformants analysed, four plants exhibited considerable GUS activities without any inductive treatment of the plants. Expression of the endogenous PR-1 genes, however, could not be detected in these plants. Primer extension analyses revealed correct initiation of the PR1/GUS hybrid transcripts from the PR-1a TATA box. When the plants were analysed at the cellular level, clear differences regarding the tissue specificity of expression of the reporter gene were observed. These results strongly suggest that the PR1/GUS hybrid promoter expression cassettes may be activated when integrated in the vicinity of heterologous enhancer elements dispersed in the tobacco genome. In order to support this hypothesis, domain B of the enhancer of the 35S RNA promoter from cauliflower mosaic virus (CaMV) was fused to various PR1/GUS hybrid genes upstream as well as downstream from the RNA start site. These constructs were stably introduced into the tobacco genome. In any primary transformant analysed, strong GUS activities were observed with the PR1/GUS hybrid RNAs originating from the normal transcription start site of the PR-1a gene. The tissue specificity of gene expression was identical to that described previously for the CaMV 35S domain B enhancer element. Thus, modulations of the transcriptional activity of the PR-1 promoter can be achieved by heterologous enhancers in transgenic plants and may be encountered upon random integration of PR-1 promoter constructs into the tobacco genome.
病程相关蛋白1（PR-1）基因可被多种环境刺激诱导，如病原体侵袭或植物接触某些化学物质。为了研究这些基因的调控机制，将PR-1a基因和两个PR-1假基因的5'侧翼区域通过转录融合连接到大肠杆菌β-葡萄糖醛酸酶（GUS）基因上。这些构建体被稳定整合到烟草基因组中，并对独立的初级转化体进行报告基因表达监测。出乎意料的是，在分析的55个转化体中，有四株植物在未对植株进行任何诱导处理的情况下表现出相当高的GUS活性。然而，在这些植物中未检测到内源性PR-1基因的表达。引物延伸分析表明，PR1/GUS杂交转录本从PR-1a TATA框正确起始。当在细胞水平上分析这些植物时，观察到报告基因表达的组织特异性存在明显差异。这些结果强烈表明，PR1/GUS杂交启动子表达盒在整合到分散于烟草基因组中的异源增强子元件附近时可能被激活。为了支持这一假设，将花椰菜花叶病毒（CaMV）35S RNA启动子增强子的B结构域与RNA起始位点上游和下游的各种PR1/GUS杂交基因融合。这些构建体被稳定导入烟草基因组。在分析的任何初级转化体中，均观察到源自PR-1a基因正常转录起始位点的PR1/GUS杂交RNA具有很强的GUS活性。基因表达的组织特异性与先前描述的CaMV 35S结构域B增强子元件相同。因此，在转基因植物中，异源增强子可实现对PR-1启动子转录活性的调控，并且在将PR-1启动子构建体随机整合到烟草基因组中时可能会出现这种情况。
