寄主植物与病原菌免疫反应的分子遗传基础

近年来,大量的植物抗病基因和病原菌无毒基因被克隆,抗病基因和无毒基因的结构、功能及其互作关系的研究也取得重大进展。在植物中,由病原菌模式分子(pathogen-associated molecular patterns, PAMPs)引发的免疫反应(PAMP-triggered immunity, PTI)和由效应因子引发的免疫反应(effector-triggered immunity, ETI)是植物在长期进化过程中形成的两类抵抗病原物的机制。PTI反应主要通过细胞表面受体(patternrecognition receptors, PRRs)识别并结合PAMPs从而激活下游免疫反应,而在ETI反应中,则通过植物R基因(resistance gene,R)与病原菌无毒基因(avirulence gene, Avr)产物间的直接或间接相互作用来完成免疫反应。本文对植物PTI反应和ETI反应分别进行了概述,重点探讨了植物R基因与病原菌Avr基因之间的互作遗传机理,并对目前植物抗性分子遗传机制研究和抗病育种中的问题进行了探讨和展望。     

植物的基因对基因抗病性学说

植物的基因对基因抗病性学说促进了寄主与病原物相互作用分子机制研究的深入。介绍近几年来对Avr基因和R基因的特性,二之间的相互作用机制以及R基因信号传导途径等方面的研究进展。     

植物病原物无毒基因及其功能

植物抗病基因与病原物无毒基因产物间直接或间接相互作用导致产生的基因对基因抗性是植物抗病性的重要形式。无毒基因已在多种植物病原物 ,包括真菌、细菌、病毒和卵菌等中得到克隆。绝大多数已克隆无毒基因之间 ,及其与已知蛋白之间 ,均无显著序列同源性。然而 ,多数已克隆植物抗病基因有较高序列一致性 ,产物往往具有相似的结构域。由序列一致性很高的抗病基因产物与没有明显序列同源性的无毒基因产物相互作用 ,介导产生的过敏性细胞坏死和抗病性 ,在产生速度、强度和组织特异性等方面均可能有显著差异。无毒基因具有双重功能 :在含互补抗病基因植物中表现无毒效应 ,而在不含互补抗病基因植物中显示小种、菌株、致病型、或种特异性毒性效应     

植物抗病基因结构、功能及其进化机制研究进展

植物与病原菌在长期的共进化和相互选择的过程中,逐渐形成了组织障碍、非寄主抗性和小种专化抗性等有效的防御机制。小种专化抗性(基因对基因抗性)主要是由植物抗病基因识别相应的病原菌无毒基因并激活植物体内抗病信号进而抵御病原菌的侵染。从目前已克隆的 70 多个抗病基因来看,它们在结构上具有高度保守性,主要包括核苷酸结合位点(NBS),亮氨酸重复结构(LRR), 蛋白激酶结构域(PK), 果蝇蛋白 Toll 和哺乳动物蛋白质白细胞介素 1 受体[interleukin(IL)-1 receptor]类似结构域(TIR), 双螺旋结构(CC)或亮氨酸拉链(LZ)和跨膜结构域(TM)等,其在抗病基因与病原菌无毒(效应)蛋白互作以及植物内部免疫信号传导中起着重要的作用。同时,抗病基因又通过基因复制、遗传重组等进化机制形成多基因家族,为植物抗病的专化性和多样性提供了重要的遗传基础。本文主要讨论了近来已克隆抗病基因的结构特征、功能以及抗病基因进化机制研究的进展。     

植物抗病分子机制研究进展

近十年来,植物抗病分子机制研究取得显著进展。综述了植物抗病基因的克隆及其结构分析、病原菌无毒基因及其相关致病因子的克隆与研究、信号传导相关因子的克隆及其结构分析以及植物-病原菌的相互作用研究,重点介绍了以植物特异抗病基因为介导的诱导防卫作用机制(包括抗病基因编码毒素蛋白,进而抑制病原菌的繁殖;显性基因编码病原菌致病性的靶标物;抗病基因表达产物直接引发抗病反应和基因对基因的抗病作用机制等)的研究进展,以期为植物抗病育种提供有益的信息。     

植物抗病分子机制研究进展

近十年来,植物抗病分子机制研究取得显著进展.综述了植物抗病基因的克隆及其结构分析、病原菌无毒基因及其相关致病因子的克隆与研究、信号传导相关因子的克隆及其结构分析以及植物-病原菌的相互作用研究,重点介绍了以植物特异抗病基因为介导的诱导防卫作用机制(包括抗病基因编码毒素蛋白,进而抑制病原菌的繁殖;显性基因编码病原菌致病性的靶标物;抗病基因表达产物直接引发抗病反应和基因对基因的抗病作用机制等)的研究进展,以期为植物抗病育种提供有益的信息.     

水稻稻瘟病抗性基因的克隆、育种利用及稻瘟菌无毒基因研究进展

稻瘟病是世界上影响水稻(Oryza sativa)粮食生产的主要病害之一, 抗病基因的发掘与利用是抗病育种的基础和核心。随着寄主水稻和病原菌稻瘟病菌(Magnaporthe oryzae)基因组测序和基因注释的完成, 水稻和稻瘟病菌的互作体系成为研究植物与真菌互作的模式系统。该文对稻瘟病抗病基因的遗传、定位、克隆及育种利用进行概述, 并通过生物信息学分析方法, 探讨了水稻全基因组中NBS-LRR类抗病基因在水稻12条染色体上的分布情况, 同时对稻瘟病菌无毒基因的鉴定及无毒蛋白与抗病蛋白的互作进行初步分析。最后对稻瘟病抗病基因研究存在的问题进行分析并展望了未来的研究方向, 以期为水稻抗稻瘟病育种发展和抗病机制的深入理解提供参考。     

大豆疫霉菌(Phytophthora sojae)无毒基因Avr1a、Avr1k及Avr3a的分子鉴定

【目的】为大豆疫霉菌(Phytophthora sojae)无毒基因Avr1a、Avr1k和Avr3a快速分子检测提供方法,也为P.sojae其它无毒基因的快速分子检测研究提供依据。【方法】依据GenBank中公布的P.sojae无毒基因Avr1a、Avr1k和Avr3a的序列设计引物,分别筛选出特异性引物,在PCR反应体系和扩增条件优化基础上,对已经接种鉴定过无毒基因Avr1a、Avr1k和Avr3a的86株P.sojae进行PCR检测,建立一套P.sojae无毒基因Avr1a、Avr1k和Avr3a的特异性检测体系。将分子鉴定和接种鉴定结果进行比对,将扩增出的真阳性条带和假阳性条带分别进行胶回收和克隆测序,测序结果分别与3个无毒基因的原序列比对,判定分子标记方法是否适于Avr1a、Avr1k和Avr3a的快速检测。【结果】筛选出的特异性引物均能从含有对应无毒基因的菌株中扩增出约550 bp的条带。Avr1a、Avr1k和Avr3a的分子鉴定及接种鉴定结果符合率依次为45.3%、84.9%和97.7%。3个无毒基因的真阳性条带序列与原序列一致性均达97%以上,Avr1a的假阳性条带与原序列一致性在80%左右,其余2个基因的都在30%以下。【结论】利用Avr1a、Avr1k和Avr3a基因序列分别设计引物建立的检测体系可以用于Avr3a的快速检测,不适于Avr1a的快速检测,是否适合Avr1k的快速检测尚不清楚。     

植物TIR-NB-LRR类型抗病基因各结构域的研究进展

植物抗病反应是一个多基因调控的复杂过程,在这个过程中R基因发挥了非常重要的作用。根据其氨基酸基序组成以及跨膜结构域的不同,R基因可以分为多种类型,其中NBS-LRR类型是植物基因组中最大的基因家族之一。TIR-NB-LRR类型的抗病基因又是NB-LRR类型中的一大类,也是目前抗病基因研究的热点。该文总结了TIR-NB-LRR类型抗病基因各个结构域的功能和相关的研究进展。相关研究表明,TIR结构域主要通过自身或异源的二聚体化介导抗性信号的转导,但也有部分研究表明,该结构域可能参与病原菌的特异性识别。NBS结构域常被认为具有"分子开关"的功能,它可以通过结合ADP或ATP来调节植物抗病蛋白的构象变化,从而调节下游抗病信号的传导。LRR结构域在植物与病原菌互作的过程中可以通过与病原菌的无毒蛋白直接或间接互作来特异识别病原菌。也有研究发现,LRR结构域具有调节信号传导的功能。这些信息将为研究植物抗病机理提供理论依据,也为将来通过基因编辑技术对作物进行定向抗病育种提供思路。     

稻瘟菌无毒基因研究进展

无毒基因编码的产物激发病原物与植物特异性相互作用。水稻与稻瘟菌之间的特异互作符合“基因对基因”关系。从研究稻瘟菌无毒基因的意义、已鉴定和克隆的稻瘟菌无毒基因、稻瘟菌无毒基因与其抗病基因的互作特点等几个方面,对稻瘟菌无毒基因研究进展作了简要评述 。     

植物与病原微生物互作分子基础的研究进展

植物在与病原微生物共同进化过程中形成了复杂的免疫防卫体系。植物的先天免疫系统可大致分为两个层面。第一个层面的免疫基于细胞表面的模式识别受体对病原物相关分子模式的识别,该免疫过程被称为病原物相关分子模式触发的免疫(PAMP-triggered immunity,PTI),能帮助植物抵抗大部分病原微生物;第二个层面的免疫起始于细胞内部,主要依靠抗病基因编码的蛋白产物直接或间接识别病原微生物分泌的效应子并且激发防卫反应,来抵抗那些能够利用效应子抑制第一层面免疫的病原微生物,这一过程被称为效应子触发的免疫(Effector-triggered immunity,ETI)。这两个层面的免疫都是基于植物对"自我"及"非我"的识别,依靠MAPK级联等信号网络,将识别结果传递到细胞核内,调控相应基因的表达,做出适当的免疫应答。本文着重阐述了植物与病原微生物互作过程中不同层面的免疫反应所发生主要事件的分子基础及研究进展。     

植物与病原微生物互作分子基础的研究进展

植物在与病原微生物共同进化过程中形成了复杂的免疫防卫体系。植物的先天免疫系统可大致分为两个层面。第一个层面的免疫基于细胞表面的模式识别受体对病原物相关分子模式的识别, 该免疫过程被称为病原物相关分子模式触发的免疫(PAMP-triggered immunity, PTI), 能帮助植物抵抗大部分病原微生物; 第二个层面的免疫起始于细胞内部, 主要依靠抗病基因编码的蛋白产物直接或间接识别病原微生物分泌的效应子并且激发防卫反应, 来抵抗那些能够利用效应子抑制第一层面免疫的病原微生物, 这一过程被称为效应子触发的免疫(Effector-triggered immunity, ETI)。这两个层面的免疫都是基于植物对“自我”及“非我”的识别, 依靠MAPK级联等信号网络, 将识别结果传递到细胞核内, 调控相应基因的表达, 做出适当的免疫应答。本文着重阐述了植物与病原微生物互作过程中不同层面的免疫反应所发生主要事件的分子基础及研究进展。     

Recent advances in plant immunity: recognition, signaling, response, and evolution

Innate immune system is employed by plants to defend against phytopathogenic microbes through specific perception of non-self molecules and subsequent initiation of resistance responses. Current researches elucidate that plants mostly rely on cell surface-located pattern recognition receptors (PRRs) and intracellular nucleotide-binding leucine-rich repeat proteins (NB-LRRs) to recognize pathogen-associated molecular patterns (PAMPs) and effector proteins from microbial pathogens, initiating PAMP- and effector-triggered immunity (PTI and ETI), respectively. Some pathogenic bacterial effector proteins are usually secreted into plant cells and play a virulence function by suppressing plant PTI, implying an evolutionary process of plant immunity from PTI to ETI. In the past several years, a great progress has been achieved to reveal fascinating molecular mechanisms underlying the pathogenic recognition, resistance signaling transduction, and plant immunity evolution. Here, we summarized the latest breakthroughs about these topics, and offered an integral understanding of plant molecular immunity.     

Role of pathogen's effectors in understanding host-pathogen interaction

Pathogens can pose challenges to plant growth and development at various stages of their life cycle. Two interconnected defense strategies prevent the growth of pathogens in plants, i.e., molecular patterns triggered immunity (PTI) and pathogenic effector-triggered immunity (ETI) that often provides resistance when PTI no longer functions as a result of pathogenic effectors. Plants may trigger an ETI defense response by directly or indirectly detecting pathogen effectors via their resistance proteins. A typical resistance protein is a nucleotide-binding receptor with leucine-rich sequences (NLRs) that undergo structural changes as they recognize their effectors and form associations with other NLRs. As a result of dimerization or oligomerization, downstream components activate “helper” NLRs, resulting in a response to ETI. It was thought that ETI is highly dependent on PTI. However, recent studies have found that ETI and PTI have symbiotic crosstalk, and both work together to create a robust system of plant defense. In this article, we have summarized the recent advances in understanding the plant's early immune response, its components, and how they cooperate in innate defense mechanisms. Moreover, we have provided the current perspective on engineering strategies for crop protection based on up-to-date knowledge.     

Toward understanding of rice innate immunity against Magnaporthe oryzae

The blast fungus, Magnaporthe oryzae, causes serious disease on a wide variety of grasses including rice, wheat and barley. The recognition of pathogens is an amazing ability of plants including strategies for displacing virulence effectors through the adaption of both conserved and variable pathogen elicitors. The pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) were reported as two main innate immune responses in plants, where PTI gives basal resistance and ETI confers durable resistance. The PTI consists of extracellular surface receptors that are able to recognize PAMPs. PAMPs detect microbial features such as fungal chitin that complete a vital function during the organism’s life. In contrast, ETI is mediated by intracellular receptor molecules containing nucleotide-binding (NB) and leucine rich repeat (LRR) domains that specifically recognize effector proteins produced by the pathogen. To enhance crop resistance, understanding the host resistance mechanisms against pathogen infection strategies and having a deeper knowledge of innate immunity system are essential. This review summarizes the recent advances on the molecular mechanism of innate immunity systems of rice against M. oryzae. The discussion will be centered on the latest success reported in plant–pathogen interactions and integrated defense responses in rice.     

Plant innate immunity: An updated insight into defense mechanism

Plants are invaded by an array of pathogens of which only a few succeed in causing disease. The attack by others is countered by a sophisticated immune system possessed by the plants. The plant immune system is broadly divided into two, viz. microbial-associated molecular-patterns-triggered immunity (MTI) and effector-triggered immunity (ETI). MTI confers basal resistance, while ETI confers durable resistance, often resulting in hypersensitive response. Plants also possess systemic acquired resistance (SAR), which provides long-term defense against a broad-spectrum of pathogens. Salicylic-acid-mediated systemic acquired immunity provokes the defense response throughout the plant system during pathogen infection at a particular site. Trans-generational immune priming allows the plant to heritably shield their progeny towards pathogens previously encountered. Plants circumvent the viral infection through RNA interference phenomena by utilizing small RNAs. This review summarizes the molecular mechanisms of plant immune system, and the latest breakthroughs reported in plant defense. We discuss the plant–pathogen interactions and integrated defense responses in the context of presenting an integral understanding in plant molecular immunity.     

植物与病原菌互作的分子机制研究进展

植物的先天免疫主要包括模式识别受体对保守的微生物病原相关分子模式的识别和抗病蛋白对效应蛋白的识别。植物与病原体互作过程中存在广泛的信号交流,信号分子在植物与病原体的互作攻防中发挥了重要的调控作用,决定了二者的竞争关系。当前,大量植物与病原体互作中的信号分子被定位和克隆,其作用方式被揭示。本文总结了这些信号分子及其在植物免疫过程中的作用机制,主要包括植物细胞表面的模式识别受体分子对病原相关分子模式的识别与应答,植物抗病蛋白对病原体效应蛋白的识别与应答,以及免疫反应下游相关信号分子及其在植物抗病中的作用。此外,本文对未来相关研究提出了展望。     

The zig-zag-zig in oomycete–plant interactions

In addition to a range of preformed barriers, plants defend themselves against microbial invasion by detecting conserved, secreted molecules, called pathogen-associated molecular patterns (PAMPs). PAMP-triggered immunity (PTI) is the first inducible layer of plant defence that microbial pathogens must navigate by the delivery of effector proteins that act to suppress or otherwise manipulate key components of resistance. Effectors may themselves be targeted by a further layer of defence, effector-triggered immunity (ETI), as their presence inside or outside host cells may be detected by resistance proteins. This 'zig-zag-zig' of tightly co-evolving molecular interactions determines the outcome of attempted infection. In this article, we consider the complex molecular interplay between plants and plant pathogenic oomycetes, drawing on recent literature to illustrate what is known about oomycete PAMPs and elicitors of defence responses, the effectors they utilize to suppress PTI, and the phenomenal molecular 'battle' between effector and resistance ( R ) genes that dictates the establishment or evasion of ETI.