植物抗病基因及其作用机理

综合近年国内外对植物抗病基因的研究和我们对水稻抗病基因的研究成果,对植物抗病基因进行归纳分类,并就其结构、功能、作用机理和信号传导进行分析和讨论.根据植物抗病基因编码蛋白的保守结构,将植物抗病基因分成NBS-LRR、eLRR-TM、eLRR-TM-pkinase、STK和其他五大类.不同类型的基因在细胞水平上的分布不一样,NBS、激酶和LRR在不同类型的基因之间结构差异也较大,但是它们通过各不相同的作用机理参与细胞对病原体的防御.     

SGTl在植物抗病反应中的功能研究进展

SGTl是多种植物抗病基因介导的抗病信号途径的必要组件。SGTl基因的突变或沉默会导致多种植物R基因介导抗病性的丧失。另外,SGTl还参与调控植物的非宿主抗性（non-host resistance）。SGTl主要作为分子伴侣或调控泛素化对植物抗病反应进行调控。本文综述了SGTl蛋白结构、SGTl在不同植物抗病反应中的重要性与作用机制,并对SGTl在植物抗病基因工程中的应用潜力进行讨论。     

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。     

SGT1在植物抗病反应中的功能研究进展

SGT1是多种植物抗病基因介导的抗病信号途径的必要组件.SGT1基因的突变或沉默会导致多种植物R基因介导抗病性的丧失.另外,SGT1还参与调控植物的非宿主抗性(non-host resistance).SGT1主要作为分子伴侣或调控泛素化对植物抗病反应进行调控.本文综述了SGT1蛋白结构、SGT1在不同植物抗病反应中的重要性与作用机制,并对SGT1在植物抗病基因工程中的应用潜力进行讨论.     

植物抗病的分子生物学基础

随着分子生物学的不断发展,人们已逐步了解植物寄主与病原之间的相互作用及植物抗病的分子机理。植物受病原侵染后出现两种类型的卫反应：局部防卫反应（过敏反应）和系统获得性防卫反应。本质素、植保素、活性氧、水杨酸等物质已被证明了在植物抗病中起了重要作用。抗病基因和防卫基因的诱导表达构成了防卫反应的遗传基础。本文综述了近年来抗病的分子生物学研究进展,并对其发展和应用前景作了展望。     

植物抗病分子机制研究进展

植物抗病机制是目前研究的热点。在长期的进化过程中,植物形成了一系列复杂有效的防御机制来抵御、破坏病原物的侵染。植物抗病基因在植物抗性反应中起着重要的作用,植物一旦监测到病原物马上起始防御反应,并伴随着植物体内一系列细胞和生理生化的变化。近年来,基因沉默作为一个重要的细胞内防御外源核酸的机制,越来越受到科学家重视。综述了植物抗病基因和基因沉默机制在植物抗病反应中的重要作用,并对研究植物抗病机制的前景做了展望。     

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.     

植物病原菌效应子的研究进展

病原菌为了成功侵入并在寄主植物中繁殖,会分泌效应子作为入侵武器.不同病原菌的效应子具有一定的共性和异性.开展植物病原菌效应子的系统鉴定,深入揭示效应子对病原菌侵入和在植物发病中的作用以及解析效应子与植物抗病基因的互作,可为研究病原菌的致病机制及其与植物的互作提供重要的研究线索,在植物病理和抗病遗传育种研究中也具有重要理论价值和实践意义.近年来,随着测序技术的不断发展,基因组学和转录组学在植物抗病研究中的应用也日益广泛,其研究结果可为鉴定病原物致病基因、植物抗病基因、阐明病原菌与植物互作的分子机制提供重要信息.本文根据近年来植物包括树木中病原物效应子的研究进展,对效应子的特点、鉴定方法、功能及宿主抗病机理等进行了综述和比较,重点阐述了效应子的鉴定、致病功能及与植物抗病基因的分子互作和调控,并对效应子在植物抗病中的应用及其研究前景进行了展望.     

植物抗病基因同源序列及其在抗病基因克隆与定位中的应用

近10年来已有20多个植物抗病基因被克隆,测序,这些抗病基因所编码的蛋白中大多含有核苷酸结合位点,富含亮氨酸重复序列,蛋白激酶,亮氨酸拉链结构,跨膜结构域,Toll白介素－1区域等保守结构域。利用这些保守结构域合成PCR引物,已扩增出大量的植物抗病基因同源序列（RGA）。对RGA与抗病基因的关系进行了分析,讨论了RGA在研究抗病基因进化中的作用,指出RGA在抗病基因定位和转基因中具有重要意义。     

Analysis of non-TIR NBS-LRR resistance gene analogs in <Emphasis Type="Italic">Musa acuminata</Emphasis> Colla: Isolation,RFLP marker development,and physical mapping

Background  

Many commercial banana varieties lack sources of resistance to pests and diseases, as a consequence of sterility and narrow genetic background. Fertile wild relatives, by contrast, possess greater variability and represent potential sources of disease resistance genes (R-genes). The largest known family of plant R-genes encode proteins with nucleotide-binding site (NBS) and C-terminal leucine-rich repeat (LRR) domains. Conserved motifs in such genes in diverse plant species offer a means for isolation of candidate genes in banana which may be involved in plant defence.     

The plant genetic background affects the efficiency of the pepper major nematode resistance genes Me1 and Me3

Key message

The plant genetic background influences the efficiency of major resistance genes to root-knot nematodes in pepper and has to be considered in breeding strategies.

Abstract

Root-knot nematodes (RKNs), Meloidogyne spp., are extremely polyphagous plant parasites worldwide. Since the use of most chemical nematicides is being prohibited, genetic resistance is an efficient alternative way to protect crops against these pests. However, nematode populations proved able to breakdown plant resistance, and genetic resources in terms of resistance genes (R-genes) are limited. Sustainable management of these valuable resources is thus a key point of R-gene durability. In pepper, Me1 and Me3 are two dominant major R-genes, currently used in breeding programs to control M. arenaria, M. incognita and M. javanica, the three main RKN species. These two genes differ in the hypersensitive response induced by nematode infection. In this study, they were introgressed in either a susceptible or a partially resistant genetic background, in either homozygous or heterozygous allelic status. Challenging these genotypes with an avirulent M. incognita isolate demonstrated that (1) the efficiency of the R-genes in reducing the reproductive potential of RKNs is strongly affected by the plant genetic background, (2) the allelic status of the R-genes has no effect on nematode reproduction. These results highlight the primary importance of the choice of both the R-gene and the genetic background into which it is introgressed during the selection of new elite cultivars by plant breeders.     

Structure and evolution of plant disease resistance genes

This article reviews recent advances that shed light on plant disease resistance genes, beginning with a brief overview of their structure, followed by their genomic organization and evolution. Plant disease resistance genes have been exhaustively investigated in terms of their structural organization, sequence evolution and genome distribution. There are probably hundreds of NBS-LRR sequences and other types of R-gene-like sequences within a typical plant genome. Recent studies revealed positive selection and selective maintenance of variation in plant resistance and defence-related genes. Plant resistance genes are highly polymorphic and have diverse recognition specificities. R-genes occur as members of clustered gene families that have evolved through duplication and diversification. These genes appear to evolve more rapidly than other regions of the genome, and domains such as the leucine-rich repeat, are subject to adaptive selection     

Characterization and mapping of NBS-LRR resistance gene analogs in apricot (Prunus armeniaca L.)

Genomic DNA sequences sharing homology with the NBS-LRR (nucleotide binding site-leucine-rich repeat) resistance genes were isolated and cloned from apricot (Prunus armeniaca L.) using a PCR approach with degenerate primers designed from conserved regions of the NBS domain. Restriction digestion and sequence analyses of the amplified fragments led to the identification of 43 unique amino acid sequences grouped into six families of resistance gene analogs (RGAs). All of the RGAs identified belong to the Toll-Interleukin receptor (TIR) group of the plant disease resistance genes (R-genes). RGA-specific primers based on non-conserved regions of the NBS domain were developed from the consensus sequences of each RGA family. These primers were used to develop amplified fragment length polymorphism (AFLP)-RGA markers by means of an AFLP-modified procedure where one standard primer is substituted by an RGA-specific primer. Using this method, 27 polymorphic markers, six of which shared homology with the TIR class of the NBS-LRR R-genes, were obtained from 17 different primer combinations. Of these 27 markers, 16 mapped in an apricot genetic map previously constructed from the self-pollination of the cultivar Lito. The development of AFLP-RGA markers may prove to be useful for marker-assisted selection and map-based cloning of R-genes in apricot.     

Quantitative proteomic analysis of bean plants infected by a virulent and avirulent obligate rust fungus

Plants appear to have two types of active defenses, a broad-spectrum basal system and a system controlled by R-genes providing stronger resistance to some pathogens that break the basal defense. However, it is unknown if the systems are separate entities. Therefore, we analyzed proteins from leaves of the dry bean crop plant Phaseolus vulgaris using a high-throughput liquid chromatography tandem mass spectrometry method. By statistically comparing the amounts of proteins detected in a single plant variety that is susceptible or resistant to infection, depending on the strains of a rust fungus introduced, we defined basal and R-gene-mediated plant defenses at the proteomic level. The data reveal that some basal defense proteins are potential regulators of a strong defense weakened by the fungus and that the R-gene modulates proteins similar to those in the basal system. The results satisfy a new model whereby R-genes are part of the basal system and repair disabled defenses to reinstate strong resistance.     

Comparative analysis of NBS domain sequences of NBS-LRR disease resistance genes from sunflower, lettuce, and chicory

Plant resistance to many types of pathogens and pests can be achieved by the presence of disease resistance (R) genes. The nucleotide binding site-leucine rich repeat (NBS-LRR) class of R-genes is the most commonly isolated class of R-genes and makes up a super-family, which is often arranged in the genome as large multi-gene clusters. The NBS domain of these genes can be targeted by polymerase chain reaction (PCR) amplification using degenerate primers. Previous studies have used PCR derived NBS sequences to investigate both ancient R-gene evolution and recent evolution within specific plant families. However, comparative studies with the Asteraceae family have largely been ignored. In this study, we address recent evolution of NBS sequences within the Asteraceae and extend the comparison to the Arabidopsis thaliana genome. Using multiple sets of primers, NBS fragments were amplified from genomic DNA of three species from the family Asteraceae: Helianthus annuus (sunflower), Lactuca sativa (lettuce), and Cichorium intybus (chicory). Analysis suggests that Asteraceae species share distinct families of R-genes, composed of genes related to both coiled-coil (CC) and toll-interleukin-receptor homology (TIR) domain containing NBS-LRR R-genes. Between the most closely related species, (lettuce and chicory) a striking similarity of CC subfamily composition was identified, while sunflower showed less similarity in structure. These sequences were also compared to the A. thaliana genome. Asteraceae NBS gene subfamilies appear to be distinct from Arabidopsis gene clades. These data suggest that NBS families in the Asteraceae family are ancient, but also that gene duplication and gene loss events occur and change the composition of these gene subfamilies over time.     

三浅裂野牵牛NBS类抗病基因同源序列的克隆与分析

NBS类植物抗病基因保守结构域的克隆为利用简并引物扩增抗病基因同源序列提供了可能.根据抗病基因Gro1-4、Gpa2、N等的P-loop和GLPL保守结构域设计简并引物,分离甘薯近缘野生种三浅裂野牵牛NBS类型抗病基因同源序列,共获得6条相关序列,核苷酸序列的相似性为48%~97%,推测氨基酸序列的相似性在25.2%~95.1%之间.系统进化分析表明,6条三浅裂野牵牛RGA序列可分为2个不同的类群:TIR-NBS和non-TIR-NBS.三浅裂野牵牛RGA序列与源自甘薯的RGA序列有很高的相似性,这在一定程度上反映了三浅裂野牵牛与甘薯之间的亲缘关系.分离的6条RGA序列分别命名为ItRGA1~ItRGA6,GenBank登录号分别为DQ849027~DQ849032.