Characterization of Salicylic Acid-Binding Proteins in Plant Defense Responses

植物病害每年在全世界造成的损失估计为1000亿美元。正在开发各种策略来保护植物免受疾病的侵害。一种方法是诱导植物自身的自然防御。这种策略是有吸引力的，因为它可以提供针对广谱病原体的保护。对多种病原体的广谱抗性，称为系统获得性抗性（SAR），可以通过感染病原体或用SAR诱导天然化学品如水杨酸（SA）及其合成功能类似物、INA或BTH处理来激活。通过调控植物内源防御反应来控制病害的策略的发展对于维持农业生产和改善我们的环境和健康将是非常重要的。虽然我们对SA在抗病性中的功能的理解还远未完成，但越来越清楚的是，它的作用是复杂的。SA防御功能复杂性的增加与烟草中发现的SA相互作用的多种蛋白质相匹配。了解SA在防御微生物病原体中的功能将需要鉴定和表征这些蛋白质，这是本研究的主要目标。 本项目的重点是SABP 2和SABP 3。SABP 3是烟草叶绿体中的碳酸酐酶（CA）。第一个目标是完成SABP 2的克隆。已获得SABP 2的七个肽段的序列，并正在用于其基因的克隆。当务之急是确定SABP 2在抗病性中的作用。这将通过使用基于PVX的沉默系统沉默其表达和/或通过获得拟南芥中相应基因的敲除突变来完成。 该项目的第二个主要目标是确定SABP 3/CA的抗氧化活性的性质以及SA是否改变该活性。将采用几种方法。目前已有反义CA转基因烟草，其碳酸酐酶活性降低98-99%。这些植物将测试它们对氧化应激的敏感性和对病原体的抵抗力。此外，还将测试SABP 3/CA对烟草抗氧化活性的影响。为此，将使用命名为Dnce 103的酵母突变株。Dnce 103由于其CA样基因的缺失而对氧化应激非常敏感。在该突变体中表达的SABP 3/CA克服了其对氧的敏感性。希望SA能够改变SABP 3/CA对该突变体的作用。

Plant disease causes an estimated loss worldwide of $100B annually. A variety of strategies are being developed to protect plants against disease. One approach is to induce the plant's own natural defenses. This strategy is attractive since it can provide protection against a broad spectrum of pathogens. Broad-spectrum resistance to a wide array of pathogens, know as systemic acquired resistance (SAR), can be activated by infection with a pathogen or treatment with SAR-inducing natural chemicals such as salicylic acid (SA) and its synthetic functional analogues, INA or BTH. The development of strategies that control disease by manipulating endogenous plant defense responses will be very important for sustaining agricultural production and improving our environment and health.It is now well established that SA plays a key role(s) in the development of resistance in many, but not all, plant-pathogen systems. While our understanding of SA function(s) in disease resistance is far from complete, it is becoming increasingly clear that its role(s) is complex. This increase in the complexity of SA function(s) in defense is matched by the discovery in tobacco of multiple proteins with which SA interacts. An understanding of SA function(s) in defense against microbial pathogens will require the identification and characterization of these proteins, the major objective of this research. This project focuses on SABP2 and SABP3. SABP3 was recently shown to be the tobacco carbonic anhydrase (CA) that is located in the chloroplasts. The first objective is the completion of the cloning of SABP2. The sequence of seven peptides of SABP2 have been obtained and are being used to clone its gene. High priority will be to determine SABP2's role in disease resistance. This will be done by silencing its expression using the PVX-based silencing system and/or by obtaining a knockout mutation in the corresponding gene in Arabidopsis. The second major objective of this project is to determine the nature of SABP3/CA's anti-oxidant activity and whether SA alters this activity. Several approaches will be used. Currently there are available antisense CA transgenic tobacco, which have 98-99% reduction in their carbonic anhydrase enzymatic activity. These plants will be tested for their sensitivity to oxidative stress and resistance to pathogens. In addition, the effects on tobacco SABP3/CA's anti-oxidant activity will be tested. For this a mutant strain of yeast, designated Dnce103, will be employed. Dnce103 is very sensitive to oxidative stress due to a deletion of its CA-like gene. SABP3/CA expressed in this mutant overcomes its sensitivity to oxygen. It is hoped that SA will alter SABP3/CA's effect on this mutant.