水稻抗白叶枯病的分子基础

水稻的白叶枯病抗性符合基因对基因模式。在水稻中已经确定了19个抗病基因（R基因），其中Xa1和Xa21已被克隆并得到了深入的研究。同时在黄单胞杆菌水稻致病变种（Xanthomonas oryzae pv.oryzae,Xoo）中已克隆到了4个无毒基因（Avr基因）。本文以水稻的广谱白叶枯病抗病基因Xa21基因为主，综述了水稻R基因的起源、进化、抗性特异性，病原菌Avr基因的进化，R基因和Avr基因之间的互作以及由于这种互作而导致水稻对白叶枯病抗性的分子机制，并对通过基因工程利用R基因和Avr基因增育抗病水稻种质的策略进行了讨论。     

稻瘟病菌无毒基因序列变异研究进展

稻瘟病是水稻生产上的重要病害,稻瘟病菌无毒基因与水稻抗病基因间符合基因对基因学说,当寄主的抗病基因产物直接或间接识别稻瘟病菌的无毒基因产物时,可激发寄主产生过敏性坏死反应。在病原菌的致病系统中,无毒基因不稳定,经常发生变异,无毒基因的变异导致其逃脱寄主抗病基因的识别,抗病品种丧失抗病性。因此,了解无毒基因的变异机制对于培育抗病品种是至关重要的。无毒基因的变异机制主要包括点突变、缺失、插入、复制、移码突变等。目前,无毒基因AVR1-CO39,PWL,AVR-Pita的变异机制报道较多,ACE1,Avr Piz-t,AVR-Pia,AVR-Pii,AVR-Pik/km/kp的变异机制报道较少。     

植物病原物无毒基因研究进展

无毒基因编码的产物激发病原物与植物特异性相互作用,从而导致植物抗性反应。无毒基因已在细菌、真菌、病毒和卵菌等多种植物病原物中得到克隆。无毒基因不但能与抗病基因互作激发植物抗性反应,而且还可能对病原物本身具有其他生理功能。     

稻瘟病菌效应蛋白与水稻互作研究现状及展望

水稻是世界上最重要的粮食作物之一，水稻安全生产关乎食品安全问题。由稻瘟病菌引起的稻瘟病是一种世界性的真菌病害，给水稻生产造成严重损失。相较于药物防治，抗病品种的培育与应用是控制该病害最为经济有效的方法。然而，田间稻瘟病菌群体复杂多样、杀菌剂过量施用、气候环境变化等因素造成小种变异迅速，品种的抗性往往只能维持 3~5 年。稻瘟病菌通过无毒基因的变异产生新的生理小种，逃逸或抑制水稻的免疫系统，实现侵染致病。目前已在稻瘟菌中鉴定出 26 个无毒基因，其中 14 个已被克隆，其在病原菌的侵染、定殖和干扰寄主免疫反应过程中发挥重要作用，稻瘟菌效应蛋白和水稻抗性蛋白的互作分子机理研究也不断深入。研究稻瘟菌的致病机理及其与水稻互作的分子机制有助于更好地理解病原菌的作用途径和植物抗病基因响应的免疫反应，以制定更高效、绿色的防治措施。本文综述了近年来稻瘟病菌效应蛋白在水稻细胞转运和分泌的过程、效应蛋白与抗病蛋白互作的研究进展和效应蛋白的区域性分布，讨论和展望了当前研究面临的机遇和 挑战，以期为水稻与稻瘟病菌互作的分子机理研究、抗病育种及病害防控策略提供借鉴。     

番茄细菌性斑点病抗病信号传导途径的研究进展

番茄细菌性斑点病是一种严重影响番茄质量和产量的世界性细菌性病害。目前对番茄与病原菌互作的研究取得了很大进展。番茄的Pto基因是指在基因对基因学说中,对引起番茄细菌性斑点病带有AvrPto基因的致病菌Pseudomonassyingaepv.tomato(PST)起抗性作用的基因。番茄中的抗病基因Pto与病原物中的无毒基因AvrPto互作是寄主对病原物互作的典型模式系统。这一模式识别的分子机制是Pto激酶与PST的两个效应子AvrPto和AvrPtoB中的任一个发生物理互作,然后与Prf一起激活下游多重信号传导途径,进而产生抗病性反应。已基本弄清Pto抗性传导途径,但对这个途径中的许多元件的作用及环节还有待于进一步研究。     

植物三型信号分泌系统下的抗病基因防御机制

近年来随着对植物抗病机理及信号转导途径的深入研究和探索,以及通过分子生物学手段新的抗病基因和病原菌无毒基因不断被克隆,科研人员对于植物三型信号分泌系统中抗病(R)基因和无毒(Avr)基因的结构、功能,作用模式及作用机制具有更加深入的认识。深入研究病原菌—寄主之间的相互作用关系,为制定更为有效的植物病害防治措施提供了依据。该文通过对三型信号分泌系统中植物病原识别受体的组成部分,抗病基因的结构域及种类,抗病基因与无毒基因及相互作用的两种模式及具体机制的总结,从植物抗病基因角度探讨了三型信号分泌系统下植物的抗病机制并在此基础上进行了前景展望。     

疫霉菌无毒基因研究进展

病原菌的无毒基因与寄主植物的抗病基因之间的互作符合"基因对基因假说",产生的抗性是植物抗病性的重要形式。近几年,多个疫霉菌的无毒基因被快速克隆出来,使我们对疫霉菌的无毒基因有了较深入的认识。本研究介绍了植物的免疫系统与无毒基因和抗病基因之间的互作模式,详细阐述了已克隆的疫霉菌无毒基因的基本结构及其各部分的功能,结合无毒基因的序列多态性阐明了疫霉菌的毒性变异机制,并对疫霉菌无毒基因关键功能位点进行分析。     

植物病原真菌及卵菌SNAREs基因功能研究进展

植物病原真菌和卵菌产生的效应蛋白在促进病原菌侵染、操纵寄主免疫方面有关键作用,这些效应蛋白在与寄主作用之前必须被分泌出去,SNARE蛋白家族作为真核细胞内囊泡转运及膜融合的关键组分,在分子转运中有核心调控作用。随着许多植物丝状病原菌基因组被破译,对SNAREs基因参与病原菌致病机制的研究取得了可喜进展。本研究简要概述了真核生物中SNARE蛋白的组成及分类和植物病原真菌及卵菌中SNARE蛋白基因的功能研究进展,并据此提出进一步开展SNARE蛋白基因功能分析的研究建议,以期为全面、深入研究植物病原真菌和卵菌中SNARE基因的功能、理解病原菌致病、效应蛋白分泌提供新的视野,为植物-病原物互作的分子机制研究提供参考。     

禾谷刺盘孢菌在侵染早期与玉米蛋白的互作预测与分析

【目的】研究禾谷刺盘孢菌与寄主玉米的蛋白互作关系,有助于从分子水平了解病菌致病过程及病菌-寄主互作机制。【方法】采用计算方法预测病菌侵染相关蛋白与寄主玉米蛋白的互作,并结合网络可视化工具和GO注释信息对参与互作的蛋白进行深入分析。【结果】预测结果包含了355对互作蛋白,涉及16个刺盘孢菌蛋白和173个玉米蛋白,其中刺盘孢菌蛋白为蛋白酶、锌羧肽酶、木聚糖酶等潜在的致病蛋白,而病菌靶向的寄主蛋白涉及对真菌防御响应、蛋白折叠、蛋白修饰等多种生物过程。对互作蛋白信息的分析则表明预测方法既识别到已知互作,如病菌木聚糖酶与寄主木聚糖酶抑制蛋白的互作,也发现了不少新互作蛋白。【结论】这些结果为明确禾谷刺盘孢菌在侵染早期与寄主的互作机制提供了有用信息。     

水稻稻瘟病抗性变化及抗性基因克隆的研究进展

种植抗性品种是预防水稻稻瘟病最有效、最经济和环保的方式之一。目前农业生产上推广种植的抗病品种在数年内抗性减弱,甚至丢失,这可能与寄主体内的抗性基因丧失或相对应的无毒基因发生变异有关。本文综述了稻瘟病菌的致病机理、稻瘟病菌发生变异的原因、稻瘟病菌无毒基因发现与克隆以及稻瘟病的相关防治策略,以期为稻瘟病防治提供理论基础。     

利用田间抗病基因近等混合系防治马铃薯晚疫病

马铃薯是世界上第四大粮食作物,是我国七大农作物之一。晚疫病是由致病疫霉菌（Phytophthora infestans）引起的毁灭性的病害,19世纪中叶曾造成举世闻名的“爱尔兰大饥荒”,至今仍然是马铃薯最严重的病害。提高抗晚疫病的水平是马铃薯育种的重要目标。马铃薯抗晚疫病育种是通过遗传操作来抵抗植物病害的最早的人类实践之一,但至今收效甚微,从野生种导入的抗病基因在田间很容易失效。马铃薯和致病疫霉菌的互作关系符合经典的“基因对基因”假说,只有马铃薯的抗病基因和致病疫霉菌的非毒力基因同时存在并表达时,抗病反应才能发生。致病疫霉菌是一种进化潜力非常高的病原,可以快速突变本身的非毒力基因,因而造成对应的马铃薯抗病基因的失效。要提高抗病基因的持久性,目前唯一的途径是同时释放多个抗病基因,人为造成田间抗病基因的多态性。马铃薯抗晚疫病基因的克隆取得了快速的发展,为通过转基因的手段创造田间抗晚疫病基因的多态性提供了基础。     

The arms race between Magnaporthe oryzae and rice: Diversity and interaction of Avr and R genes

Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. The rice blast pathosystem is a longstanding model system for understanding plant-microbe interactions. In order to elucidate the coevolution of the host and pathogen, and provide the appropriate methods for preventing or controlling rice blast disease, researchers have focused on the evolution of virulence factors and resistance genes. Thus far, more than 30 rice blast resistance(R) genes and 12 avirulence(Avr) genes have been cloned. This review summarizes the cloned rice blast R genes, cloned Avr genes of M. oryzae and the interaction between them. This discussion also considers some of the major unanswered questions concerning this pathosystem and the opportunities for future investigations.     

Cleavage of Arabidopsis PBS1 by a bacterial type III effector

Plant disease-resistance (R) proteins are thought to function as receptors for ligands produced directly or indirectly by pathogen avirulence (Avr) proteins. The biochemical functions of most Avr proteins are unknown, and the mechanisms by which they activate R proteins have not been determined. In Arabidopsis, resistance to Pseudomonas syringae strains expressing AvrPphB requires RPS5, a member of the class of R proteins that have a predicted nucleotide-binding site and leucine-rich repeats, and PBS1, a protein kinase. AvrPphB was found to proteolytically cleave PBS1, and this cleavage was required for RPS5-mediated resistance, which indicates that AvrPphB is detected indirectly via its enzymatic activity.     

Host-parasite coevolutionary conflict between Arabidopsis and downy mildew

Plants are constantly exposed to attack by an array of diverse pathogens but lack a somatically adaptive immune system. In spite of this, natural plant populations do not often suffer destructive disease epidemics. Elucidating how allelic diversity within plant genes that function to detect pathogens (resistance genes) counteracts changing structures of pathogen genes required for host invasion (pathogenicity effectors) is critical to our understanding of the dynamics of natural plant populations. The RPP13 resistance gene is the most polymorphic gene analyzed to date in the model plant Arabidopsis thaliana. Here we report the cloning of the avirulence gene, ATR13, that triggers RPP13-mediated resistance, and we show that it too exhibits extreme levels of amino acid polymorphism. Evidence of diversifying selection visible in both components suggests that the host and pathogen may be locked in a coevolutionary conflict at these loci, where attempts to evade host resistance by the pathogen are matched by the development of new detection capabilities by the host.     

植物抗病基因类似序列的研究进展及应用策略

植物抗病基因克隆对抗病育种和抗病机制的研究具有重要意义。对已克隆出的基因研究表明,大多数的抗病基因都具有高度保守的结构域(如NBS,LRR,LZ,STK和TIR等)。根据这些保守区域设计核苷酸引物,通过PCR技术已经获得很多的RGA,然后以此为探针筛选DNA或cDNA文库,最终可获得抗病基因的候选克隆,这就是新近发展起来的同源序列克隆技术。文章简述了对抗病基因的结构特征,同源序列克隆技术及其应用策略。     

Independently evolved virulence effectors converge onto hubs in a plant immune system network

Plants generate effective responses to infection by recognizing both conserved and variable pathogen-encoded molecules. Pathogens deploy virulence effector proteins into host cells, where they interact physically with host proteins to modulate defense. We generated an interaction network of plant-pathogen effectors from two pathogens spanning the eukaryote-eubacteria divergence, three classes of Arabidopsis immune system proteins, and ~8000 other Arabidopsis proteins. We noted convergence of effectors onto highly interconnected host proteins and indirect, rather than direct, connections between effectors and plant immune receptors. We demonstrated plant immune system functions for 15 of 17 tested host proteins that interact with effectors from both pathogens. Thus, pathogens from different kingdoms deploy independently evolved virulence proteins that interact with a limited set of highly connected cellular hubs to facilitate their diverse life-cycle strategies.     

NBS-LRR Proteins and Their Partners:Molecular Switches of Plant Defense

Specificity of the plant innate immune system is often conferred by resistance（R）proteins.Most plant disease resistance （R）proteins contain a series of leucine-rich repeats（LRRs）,a nucleotide-binding site（NBS）,and a putative amino-terminal signaling domain.They are termed NBS-LRR proteins.The LRRs are mainly involved in recognition,and the amino-terminal domain determines signaling specificity,whereas the NBS domain presumably functions as a molecular switch.During the past years,the most important discoveries are the role of partners in NBS-LRR gene mediated defenses,mounting support for the so-called＂guard hypothesis＂of R gene function,and providing evidence for intramolecular interactions and intermolecular interactions within NBS- LRR proteins as a mode of signaling regulation.The outcome of these interactions determines whether a plant activates its defense responses.     

Cladosporium Avr2 inhibits tomato Rcr3 protease required for Cf-2-dependent disease resistance

How plants recognize pathogens and activate defense is still mysterious. Direct interaction between pathogen avirulence (Avr) proteins and plant disease resistance proteins is the exception rather than the rule. During infection, Cladosporium fulvum secretes Avr2 protein into the apoplast of tomato leaves and, in the presence of the extracellular leucine-rich repeat receptor-like Cf-2 protein, triggers a hypersensitive response (HR) that also requires the extracellular tomato cysteine protease Rcr3. We show here that Avr2 binds and inhibits Rcr3 and propose that the Rcr3-Avr2 complex enables the Cf-2 protein to activate an HR.