Takahashi H, Chen Z, Du H, Liu Y, Klessig D F
Department of Molecular Biology and Biochemistry, Rutgers, State University of New Jersey, Piscataway 08855-0759, USA.
Plant J. 1997 May;11(5):993-1005. doi: 10.1046/j.1365-313x.1997.11050993.x.
Numerous studies argue that salicylic acid (SA) is an important component of the plant signal transduction pathway(s) leading to disease resistance. The discovery that the SA-binding protein is a catalase, whose activity is blocked by SA, led to the proposal that one of SA's modes of action is to inhibit this H2O2-degrading enzyme and thus elevate H2O2 levels. To test this model, an attempt was made to mimic the action of SA by reducing the synthesis of catalase using antisense RNA technology. Analyses of transgenic tobacco plants that expressed the tobacco catalase 1 (cat1) or catalase 2 (cat2) gene in an antisense orientation indicate that there is no correlation between modest to high levels of reduction in catalase activity and activation of plant defenses such as pathogenesis-related (PR)-1 protein synthesis. However, three independent antisense catalase transgenic plants (ASCAT1 Nos 16, 17, and 28), which exhibited the most severe reduction in catalase activity (approximately 90% or more), developed chlorosis or necrosis on some of their lower leaves. These same leaves accumulated very high levels of PR-1 proteins and showed enhanced resistance to tobacco mosaic virus. Necrosis and elevated SA, which appear to result from severe depression of catalase levels, may be responsible for the induction of these defense responses.
大量研究表明，水杨酸（SA）是植物信号转导途径中导致抗病性的重要组成部分。SA结合蛋白是一种过氧化氢酶，其活性被SA阻断，这一发现导致了这样一种观点，即SA的作用模式之一是抑制这种H2O2降解酶，从而提高H2O2水平。为了验证这一模型，人们尝试通过使用反义RNA技术减少过氧化氢酶的合成来模拟SA的作用。对以反义方向表达烟草过氧化氢酶1（cat1）或过氧化氢酶2（cat2）基因的转基因烟草植株的分析表明，过氧化氢酶活性从适度降低到高度降低与植物防御激活（如病程相关蛋白（PR）-1蛋白合成）之间没有相关性。然而，三个独立的反义过氧化氢酶转基因植株（ASCAT1编号16、17和28），其过氧化氢酶活性降低最为严重（约90%或更多），在其一些下部叶片上出现了黄化或坏死。这些相同的叶片积累了非常高水平的PR-1蛋白，并表现出对烟草花叶病毒的抗性增强。坏死和SA水平升高，似乎是由于过氧化氢酶水平严重降低所致，可能是这些防御反应诱导的原因。
