Lawton K, Weymann K, Friedrich L, Vernooij B, Uknes S, Ryals J
Biotechnology Research Unit, CIBA-GEIGY Corporation, Research Triangle Park, NC 27709, USA.
Mol Plant Microbe Interact. 1995 Nov-Dec;8(6):863-70. doi: 10.1094/mpmi-8-0863.
Systemic acquired resistance (SAR) is an inducible plant response to infection by a necrotizing pathogen. In the induced plant, SAR provides broad-spectrum protection against not only the inducing pathogen, but also against other, unrelated pathogens. Both salicylic acid (SA) and SAR-gene expression have been implicated as playing important roles in the initiation and maintenance of SAR. Here, we describe the characterization of transgenic Arabidopsis plants that express the bacterial nahG gene encoding salicylate hydroxylase, an enzyme that can metabolize SA. Strong, constitutive expression of this gene prevents pathogen-induced accumulation of SA and the activation of SAR by exogenous SA. We show that SAR in Arabidopsis can be induced by inoculation with Pseudomonas syringe pv. tomato against infection by a challenge inoculation with Peronospora parasitica. This response is abolished in transgenic, nahG-expressing Arabidopsis, but not in ethylene-insensitive mutants. These experiments support the critical role of SA in SAR and show that ethylene sensitivity is not required for SAR induction. The NahG Arabidopsis plants will be important for future studies aimed at understanding the role of SA in plant disease resistance mechanisms.
系统获得性抗性（SAR）是植物对坏死性病原体感染的一种可诱导反应。在被诱导的植物中，SAR不仅能为植物提供针对引发感染的病原体的广谱保护，还能抵御其他不相关的病原体。水杨酸（SA）和SAR基因表达均被认为在SAR的启动和维持过程中发挥着重要作用。在此，我们描述了表达细菌nahG基因的转基因拟南芥植株的特性，nahG基因编码水杨酸羟化酶，该酶能够代谢SA。该基因的强组成型表达可阻止病原体诱导的SA积累以及外源SA对SAR的激活。我们发现，用丁香假单胞菌番茄致病变种接种拟南芥可诱导其产生针对寄生霜霉激发接种的抗性。这种反应在表达nahG的转基因拟南芥中消失，但在乙烯不敏感突变体中并未消失。这些实验支持了SA在SAR中的关键作用，并表明SAR诱导不需要乙烯敏感性。NahG拟南芥植株对于未来旨在了解SA在植物抗病机制中作用的研究将具有重要意义。
