Tornero P, Gadea J, Conejero V, Vera P
Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica-Consejo Superior de Investigaciones Científicas, Valencia, Spain.
Mol Plant Microbe Interact. 1997 Jul;10(5):624-34. doi: 10.1094/MPMI.1997.10.5.624.
Pathogenesis-related (PR) proteins form a heterogeneous family of plant proteins that are likely to be involved in defense and are inducible by pathogen attacks. One group of PRs, represented by the subfamily PR-1, are low-molecular-weight proteins of unknown biochemical function. Here we describe the cloning and characterization of two closely related genes encoding a basic and an acidic PR-1 protein (PR1b1 and PR1a2) from tomato (Lycopersicon esculentum). We present a comparative study of the mode of transcriptional regulation of these two genes in transgenic tobacco plants using a series of promoter-GUS fusions. Unexpectedly, the chimeric PR1a2/GUS gene is not induced by pathogenic signals but instead shows constitutive expression with a reproducible developmental expression pattern. It is expressed in shoot meristems, trichomes, and cortical cells as well as in vascular and nearby tissues of the mature stem. This constitutive expression pattern may represent preemption of plant defenses against potential pathogens. Conversely, the chimeric PR1b1/GUS gene does not show any constitutive expression in the plant, but it is transcriptionally activated following pathogen attack. Upon infection by tobacco mosaic virus, the PR1b1 gene is strongly activated locally in tissues undergoing the hypersensitive response but not systemically in uninoculated tissues. Furthermore, its expression is induced by both salicylic acid and ethylene precursors, two signals that coexist and apparently mediate the activation of local defenses during the hypersensitive response. We speculate that the different mode of expression of the two genes presented here, together with that reported previously for the induction of other PR-1 genes in systemic, uninoculated tissues, may all be complementary and necessary for the plant to acquire an efficient refractory state to resist pathogen attacks.
病程相关（PR）蛋白构成了一个植物蛋白的异质家族，可能参与防御反应，并可由病原体攻击诱导产生。以PR-1亚家族为代表的一类PR蛋白是生化功能未知的低分子量蛋白。本文描述了从番茄（Lycopersicon esculentum）中克隆和鉴定两个密切相关的基因，它们分别编码一种碱性PR-1蛋白和一种酸性PR-1蛋白（PR1b1和PR1a2）。我们使用一系列启动子-GUS融合构建体，对这两个基因在转基因烟草植物中的转录调控模式进行了比较研究。出乎意料的是，嵌合的PR1a2/GUS基因不受病原信号诱导，而是呈现出可重复的发育表达模式的组成型表达。它在茎尖分生组织、毛状体、皮层细胞以及成熟茎的维管组织和附近组织中表达。这种组成型表达模式可能代表了植物对潜在病原体防御的预先占据。相反，嵌合的PR1b1/GUS基因在植物中未表现出任何组成型表达，但在病原体攻击后被转录激活。感染烟草花叶病毒后，PR1b1基因在发生过敏反应的组织中局部强烈激活，但在未接种的组织中没有系统激活。此外，它的表达受到水杨酸和乙烯前体的诱导，这两种信号在过敏反应中共存，显然介导了局部防御的激活。我们推测，本文所呈现的这两个基因不同的表达模式，以及先前报道的在系统的未接种组织中其他PR-1基因的诱导表达模式，可能都是互补的，并且对于植物获得有效的抗性状态以抵抗病原体攻击是必要的。
