Yu D, Xie Z, Chen C, Fan B, Chen Z
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83844-3052, USA.
Plant Mol Biol. 1999 Feb;39(3):477-88. doi: 10.1023/a:1006180708533.
We have previously shown that healthy potato plants respond poorly to salicylic acid (SA) for activating disease resistance against the late blight fungal pathogen Phytophthora infestans. However, SA is essential for the establishment of potato systemic acquired resistance (SAR) against P. infestans after treatment with the fungal elicitor arachidonic acid (AA). To understand the molecular mechanisms through which AA induces SA-dependent SAR in potato, we have recently studied the expression of potato class II catalase (Cat2St) in comparison with its tobacco homologue, Cat2Nt, which has previously been shown to bind SA. In the present study, we show that tobacco Cat2Nt is expressed at high levels and accounts for almost half of total SA-binding activity detected in tobacco leaves. In contrast, potato Cat2St is not expressed in healthy leaves, which is associated with the low SA responsiveness of potato plants for activation of disease resistance mechanisms. Upon treatment with AA, expression of potato Cat2St is induced not only in AA-treated leaves, but also in the upper untreated parts of the plants, concomitant with the establishment of SA-dependent SAR to P. infestans. Moreover, expression of the tobacco Cat2Nt gene in transgenic potato plants leads to constitutive expression of the endogenous potato Cat2St gene and is associated with enhanced resistance to P. infestans. These results collectively indicate that plant SA-binding class II catalases may play an important role in the development of disease resistance, possibly by serving as biological targets of SA.
我们之前已经表明，健康的马铃薯植株对水杨酸（SA）激活针对晚疫病真菌病原体致病疫霉的抗病性反应不佳。然而，在用真菌激发子花生四烯酸（AA）处理后，SA对于马铃薯建立针对致病疫霉的系统获得性抗性（SAR）至关重要。为了了解AA在马铃薯中诱导SA依赖性SAR的分子机制，我们最近研究了马铃薯II类过氧化氢酶（Cat2St）与其烟草同源物Cat2Nt的表达情况，之前已表明Cat2Nt能结合SA。在本研究中，我们发现烟草Cat2Nt高水平表达，几乎占烟草叶片中检测到的总SA结合活性的一半。相比之下，马铃薯Cat2St在健康叶片中不表达，这与马铃薯植株激活抗病机制的低SA反应性有关。用AA处理后，马铃薯Cat2St的表达不仅在AA处理的叶片中被诱导，而且在植株上部未处理的部分也被诱导，同时建立了对致病疫霉的SA依赖性SAR。此外，烟草Cat2Nt基因在转基因马铃薯植株中的表达导致内源性马铃薯Cat2St基因的组成型表达，并与对致病疫霉的抗性增强相关。这些结果共同表明，植物SA结合II类过氧化氢酶可能在抗病性发展中起重要作用，可能是作为SA的生物学靶点。
