植物广谱抗病基因工程策略与研究进展

系统获得性抗性（SAP）是植物防御病原微生物侵染的一条有效途径。利用基因工程技术改造其表达特性可以提高植物的抗病性,从活性氧的代谢,抗病基因的利用、过敏反应的诱导和SAR的组成性表达等方面论述了植物广谱抗病基因工程的研究策略。已取得的成就及今后的研究方向。     

萝卜种质资源对黑腐病的抗性鉴定与筛选

对40份初选萝卜种质分别接种Xcc8004和XccBJ两个菌株,进行黑腐病苗期抗性鉴定,对其中8份代表性萝卜种质肉质根切片接种Xcc8004进行抗性鉴定和27份萝卜种质幼苗接种8个效应物基因进行过敏反应鉴定。结果表明:不同萝卜种质苗期对黑腐病的抗性存在显著差异,筛选出高抗Xcc8004的材料3份、抗病1份、中抗4份,高抗XccBJ的材料1份、抗病2份、中抗5份。萝卜苗期对Xcc8004和XccBJ的抗病性极显著相关,幼苗和肉质根对Xcc8004的抗病性极显著相关。筛选出17份对不同效应物表现过敏反应的萝卜种质。对效应物XC₀241表现过敏反应的种质数最多,对XC₀542和XC₀541表现过敏反应的种质数次之。不同抗源对不同效应物的过敏反应程度有所不同。稳定可靠抗病资源的获得为萝卜抗病育种和抗病机理的深入研究提供了基础材料。     

植物类病变坏死突变体及其基因的研究进展

在植物中类病变坏死突变现象广泛存在,突变体植株在无病害侵染也未受逆境或损伤的条件下自发形成与病原物侵染后坏死类似的症状,它们与植物抗病及细胞程序化死亡相关,并可能增强系统抗病性。综述了几种植物的典型类病变坏死突变体及其基因的研究情况,探讨了其发生的机制并对今后的应用前景进行了展望。     

植物抗病相关启动子及其研究进展

启动子是调控基因表达的重要顺式元件。植物抗病相关启动子的调控特性研究、分离及其应用对于提高植物抗病性极其关键。本文综述了植物基因启动子的基本结构、克隆方法,着重介绍了组成型、组织特异型、天然与人工合成的病原诱导型启动子的研究进展,及其在植物抗病基因工程中的应用现状和存在问题,并展望了植物抗病相关启动子的应用前景。     

拟南芥NDR1基因介导的广谱抗病性研究进展

抗病基因的研究是抗病育种及防治植物病害的基础。拟南芥NDR1(Non-race-specific disease resistance 1)基因,编码一个质膜定位蛋白,在R基因介导的抗性中具有重要作用。NDR1能与CC-NB-LRR(卷曲螺旋核酸结合或富亮氨酸重复)类抗病蛋白相互作用。以拟南芥抗病基因NDR1及其蛋白结构的研究进展为基础,综述了NDR1的广谱抗病性和抗病分子机理。     

植物诱导抗病基因工程

概述了植物诱导抗病性的诱导因子和诱导方法,植物诱导抗病性的简要机制,以及植物抗病基因工程的理论构思和应用前景。     

林木抗病基因工程研究进展

植物抗病性是当前植物病理学中研究的热点和难点之一。着重讨论植物抗病机制、抗病基因的转化方法及其在林木抗病基因工程中的应用情况,并对现阶段林木抗病基因工程中存在的主要问题和应用前景进行了讨论。     

植物类病变突变体的诱发与突变机制

植物类病变突变体（lesion mimic mutant,LMM）是在无明显逆境或病原物侵染时,植物自发地形成类似病斑的一类突变体。它涉及到细胞程序性死亡（programmed cell death,PCD）,往往能提高植物的抗病能力。因此,它对于揭示植物抗病反应机制,增加植物的广谱抗性具有重要意义。现就植物类病变突变体的诱发与表型特点、突变基因的分子定位与克隆及类病变表型的形成机制研究进展作一简要综述,以期为植物细胞程序性死亡机制和抗病分子作用机制研究提供有益的信息。     

PCR-RAPD分子生物学技术及其在植物抗病性研究中的应用

PCR—RAPD技术是一种高效的基因组DNA多态性分析技术,能够在对生物细胞或组织中DNA遗传多样性、亲缘关系及系统进化分子标记检测的同时进行基因定位与遗传作图。本综述了PCR—RAPD技术的基本原理和应用范围,以及近年来在植物抗感病品种(品系)间亲缘远近关系分析、植物抗病性遗传基因的DNA分子标记与检测、植物抗病基因的标记和定位、植物抗病基因的分离与克隆、植物抗病育种的分子标记辅助选择与检测等植物抗病性分子机制研究方面的应用,并对该技术所存在的问题及应用前景进行了探讨。     

植物NBS类抗病基因的进化

NBS(Nucleotide-binding site)类抗病基因是植物中最重要的一类抗病基因, 其进化模式、结构特点和功能调控一直是抗病基因研究领域的热点。这类基因具有保守的结构域, 广泛存在于植物基因组中, 在不同植物基因组中数目差异较大且具有较低的表达量。此外, 同源NBS类抗病基因之间通过频繁的序列交换产生广泛的序列多样性, 且抗病基因位点具有较差的线性。依据基因之间序列交换的频率, 抗病基因可分为TypeⅠ和TypeⅡ两类。文章从抗病基因的结构、数量、分布、序列多样性、进化模式以及表达调控等方面进行了综述, 旨在为后续NBS类抗病基因的相关研究提供参考。     

A locus on mouse chromosome 6 that determines resistance to herpes simplex virus also influences reactivation, while an unlinked locus augments resistance of female mice

During studies to determine a role for tumor necrosis factor (TNF) in herpes simplex virus type 1 (HSV-1) infection using TNF receptor null mutant mice, we discovered a genetic locus, closely linked to the TNF p55 receptor (Tnfrsf1a) gene on mouse chromosome 6 (c6), that determines resistance or susceptibility to HSV-1. We named this locus the herpes resistance locus, Hrl, and showed that it also mediates resistance to HSV-2. Hrl has at least two alleles, Hrl(r), expressed by resistant strains like C57BL/6 (B6), and Hrl(s), expressed by susceptible strains like 129S6 (129) and BALB/c. Although Hrl is inherited as an autosomal dominant gene, resistance to HSV-1 is strongly sex biased such that female mice are significantly more resistant than male mice. Analysis of backcrosses between resistant B6 and susceptible 129 mice revealed that a second locus, tentatively named the sex modifier locus, Sml, functions to augment resistance of female mice. Besides determining resistance, Hrl is one of several genes involved in the control of HSV-1 replication in the eye and ganglion. Remarkably, Hrl also affects reactivation of HSV-1, possibly by interaction with some unknown gene(s). We showed that Hrl is distinct from Cmv1, the gene that determines resistance to murine cytomegalovirus, which is encoded in the major NK cell complex just distal of p55 on c6. Hrl has been mapped to a roughly 5-centimorgan interval on c6, and current efforts are focused on obtaining a high-resolution map for Hrl.     

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.     

Ecological costs of biotrophic versus necrotrophic pathogen resistance, the hypersensitive response and signal transduction

Recent advances along numerous research avenues show that plant interactions with biotrophic and necrotrophic pathogens use similar pathways with opposing effects. The hypersensitive response is associated with increased biotroph resistance but decreased necrotroph resistance. In plant/herbivore interactions, opposing effects of defenses against specialist versus generalist herbivores are controlled by plant secondary metabolites, where a metabolite that provides resistance to generalist herbivores may stimulate specialist herbivores. This multi-trophic interaction is presented as an ecological cost of plant resistance, but similar concepts are rarely applied to plant interactions with different classes of pathogens. In this review, we begin to describe how necrotrophic pathogens may place an ecological cost upon plant resistance to biotrophic pathogens. We separate these potential ecological costs into three concepts: (1) the local cost of the hypersensitive response, (2) organismal cost of having machinery for a hypersensitive response and (3) antagonism between salicylate and jasmonate signaling. We describe the literature supporting these concepts and some predictions that they generate.     

Pathogen-induced elicitin production in transgenic tobacco generates a hypersensitive response and nonspecific disease resistance.

The rapid and effective activation of disease resistance responses is essential for plant defense against pathogen attack. These responses are initiated when pathogen-derived molecules (elicitors) are recognized by the host. We have developed a strategy for creating novel disease resistance traits whereby transgenic plants respond to infection by a virulent pathogen with the production of an elicitor. To this end, we generated transgenic tobacco plants harboring a fusion between the pathogen-inducible tobacco hsr 203J gene promoter and a Phytophthora cryptogea gene encoding the highly active elicitor cryptogein. Under noninduced conditions, the transgene was silent, and no cryptogein could be detected in the transgenic plants. In contrast, infection by the virulent fungus P. parasitica var nicotianae stimulated cryptogein production that coincided with the fast induction of several defense genes at and around the infection sites. Induced elicitor production resulted in a localized necrosis that resembled a P. cryptogea-induced hypersensitive response and that restricted further growth of the pathogen. The transgenic plants displayed enhanced resistance to fungal pathogens that were unrelated to Phytophthora species, such as Thielaviopsis basicola, Erysiphe cichoracearum, and Botrytis cinerea. Thus, broad-spectrum disease resistance of a plant can be generated without the constitutive synthesis of a transgene product.     

Resistance to pathogens and host developmental stage: a multifaceted relationship within the plant kingdom

The induction of resistance to disease during plant development is widespread in the plant kingdom. Resistance appears at different stages of host development, varies with plant age or tissue maturity, may be specific or broad-spectrum and is driven by diverse mechanisms, depending on plantpathogen interactions. Studies of these forms of resistance may help us to evaluate more exhaustively the plethora of levels of regulation during development, the variability of the defense potential of developing hosts and may have practical applications, making it possible to reduce pesticide applications. Here, we review the various types of developmental resistance in plants and current knowledge of the molecular and cellular processes involved in their expression. We discuss the implications of these studies, which provide new knowledge from the molecular to the agrosystem level.     

Expression of the human NAD(P)-metabolizing ectoenzyme CD38 compromises systemic acquired resistance in Arabidopsis

Plant systemic acquired resistance (SAR) is a long-lasting, broad-spectrum immune response that is mounted after primary pathogen infection. Although SAR has been extensively researched, the molecular mechanisms underlying its activation have not been completely understood. We have previously shown that the electron carrier NAD(P) leaks into the plant extracellular compartment upon pathogen attack and that exogenous NAD(P) activates defense gene expression and disease resistance in local treated leaves, suggesting that extracellular NAD(P) [eNAD(P)] might function as a signal molecule activating plant immune responses. To further establish the function of eNAD(P) in plant immunity, we tested the effect of exogenous NAD(P) on resistance gene-mediated hypersensitive response (HR) and SAR. We found that exogenous NAD(P) completely suppresses HR-mediated cell death but does not affect HR-mediated disease resistance. Local application of exogenous NAD(P) is unable to induce SAR in distal tissues, indicating that eNAD(P) is not a sufficient signal for SAR activation. Using transgenic Arabidopsis plants expressing the human NAD(P)-metabolizing ectoenzyme CD38, we demonstrated that altering eNAD(P) concentration or signaling compromises biological induction of SAR. This result suggests that eNAD(P) may play a critical signaling role in activation of SAR.     

Recent advances in systemic acquired resistance research — a review

Little is known about the signal transduction events that lead to the establishment of the broad-spectrum, inducible plant immunity called systemic acquired resistance (SAR). Salicylic acid (SA) accumulation has been shown to be essential for the expression of SAR and plays a key role in SAR signaling. Hydrogen peroxide has been proposed to serve as a second messenger of SA. However, our results do not support such a role in the establishment of SAR. Further elucidation of SAR signal transduction has been facilitated by the identification and characterization of mutants. The lesions simulating disease (lsd) resistance response mutant class exhibits spontaneous lesions similar to those that occur during the hypersensitive response. Interestingly, some lsd mutants lose their lesioned phenotype when SA accumulation is prevented by expression of the nahG gene (encoding salicylate hydroxylase), thereby providing evidence for a feedback loop in SAR signal transduction. Characterization of a mutant non-responsive to SAR activator treatments has provided additional evidence for common signaling components between SAR and gene-for-gene resistance.