心叶烟NPR1基因全长cDNA序列的克隆及表达分析

 NPR1(non-expressor of pathogenesis-related gene 1)基因在拟南芥系统获得抗性中起着关键作用,可调控拟南芥植株广谱抗性的发生。本文报道了从心叶烟中克隆NPR1同源基因(NgNPR1)及其表达特性的研究结果。NgNPR1 cDNA全长2253 bp,编码588个氨基酸。将NgNPR1基因组全长与cDNA序列进行比对发现,NgNPR1基因组DNA含有4个外显子和3个内含子。Southern杂交分析表明,在心叶烟基因组中NgNPR1为单拷贝基因。采用绿色荧光蛋白在洋葱表皮瞬时表达的试验,证明了NgNPR1蛋白在水杨酸诱导时会从细胞质转运到细胞核中。Northern杂交分析发现,NgNPR1基因可以被与植物抗病相关的信号分子如水杨酸、茉莉酸甲酯、过氧化氢和乙烯所诱导。进一步研究发现,植物病原物如赤星病菌、青枯病菌和烟草花叶病毒对心叶烟植株的侵染也会使NgNPR1表达量增加。这些结果表明,NgNPR1基因在心叶烟植株抵御病原物侵染过程中可能起着重要作用。     

植物对虫害的系统获得性抗性及抗虫与抗病信号途径间的相互作用

受病原体感染后,植物会获得一种持久广泛的抗性,称为系统获得性抗性,受到昆虫侵害时也会获得类似的系统获得性抗性.植物系统抗虫与抗病信号分子不同,前者是茉莉酸(JA)、甲基茉莉酸(Me-JA)或系统素,而后者是水杨酸(SA).SA介导的系统抗病信号途径与JA等介导的系统抗虫信号途径并非完全独立,而是存在所谓的"交叉对话",但"交叉对话"结果是相互促进还是抑制仍不清楚.植物系统抗性信号及其互作研究无疑会完善植物保护策略.     

植物抗病防卫基因表达调控与诱导抗性遗传的机制

 植物抗病防卫基因的产物直接参加抵抗病原物侵染的活动;它们的表达调控遵循一定规律;这些规律是诱导抗性遗传方式改造的基础;对动植物获得免疫相似性的了解,对植物各类抗病机制研究与改造利用的预见性,都展示出诱导抗性遗传方式改造的意义和前景。     

植物系统性获得抗病性的产生机理和途径

坏死型病原物侵染或某些生化制剂诱导处理后,植株未受侵染或处理部位产生对随后病原物侵染的抗性,称为植物系统性获得抗性,ＳＡＲ具有抗性表现系统、持久、抗病对象广谱三大特点。坏死型病原物侵染或某些生化制剂处理后,植株受处理部位迅速产生系统性信号,经韧皮部传导到未侵染或处理部位,诱发ＳＡＲ基因表达。水杨酸是诱发ＳＡＲ的系统性信号之一。此外,上部非处理部位处于敏化状态,能更迅速有效地产生针对挑战接种病原物的     

利用植物免疫原理控制农作物病虫害研究进展

21世纪以来,植物免疫学科得到迅猛的发展,植物免疫在防御机制构成、防御反应等方面的原理不断明晰。由于植物免疫可提升农作物产量和品质、减少农药使用,在农作物病虫害控制方面显示出巨大的经济、社会和生态价值。笔者从植物免疫的起源与发展、植物免疫的作用模式等角度介绍了植物免疫的基本原理,从PAMP-PRRs、病原物效应子与植物防御物质,以及病原菌效应子与植物基因等方面阐述了病原菌—植物互作的分子机理。分析了水杨酸、茉莉酸、乙烯和油菜素内脂等信号转导通路及其功能,探讨了植物免疫在植物激活剂创制和抗病育种中的开发与应用,并对植物免疫的发展趋势及前景进行了展望。     

SA诱导拟南芥对灰霉病的抗性与木质素含量的关系

对拟南芥植株喷施水杨酸后,接种灰霉病菌(Botrytis cinerea),观察植物对病原物反应的变化。结果表明:喷施水杨酸可以降低拟南芥灰霉病的发生率。在平板培养中,水杨酸对灰霉菌分生孢子的萌发及菌丝的生长均无明显抑制作用,因此认为水杨酸处理后发病率的下降是由于水杨酸处理提高了植物的抗病性,且诱导抗性的持久期在10 d以上。观察中还发现在拟南芥叶片上喷施SA或接种灰霉菌都会使叶片PAL和POD活性上升,进而引起木质素的积累,两者在积累量上和时间程度上具较好的一致性,说明水杨酸诱导拟南芥抗灰霉病的过程中,通过PAL和POD活性的提高进而引起木质素含量的增加,可能是诱导拟南芥产生抗性的机制之一。     

植物抗病激活剂诱导植物抗病性的研究进展

植物抗病激活剂本身及其代谢物无直接的杀菌活性,但可刺激植物的免疫系统而诱导植物产生具有广谱性、持久性和滞后性的系统获得性抗病性能(SAR).植物抗病激活剂的诱导除了可以引起植物富含羟脯氨酸糖蛋白(HRGP)的变化,导致木质素在细胞壁沉积,使植物形成物理防御机制外,经植物抗病激活剂诱导后的植株能导致内源水杨酸(SA)的累积、形成氧化激增,植物局部细胞程序化死亡而产生过敏反应(HR),植物抗病激活剂诱导后产生的抗病信号经内源信号传导物质SA、茉莉酸(JA)、乙烯(Et)和一氧化氮(NO)可传导到达整个植株,经过一系列抗病相关基因的调控和表达可引起寄主防御酶系如苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶(β-1,3-glucanase)、几丁质酶(chitinase)、过氧化物酶(POX)等以及抗病物质如木质素与植保素等的变化及病程相关蛋白(PRP)的调控与表达.文中讨论了植物抗病激活剂概念和种类及其诱导抗病作用的主导机制,指出了植物抗病激活剂的应用前景和发展方向及使用和研究开发中可能存在的问题与对策.     

茉莉酸对PR-1、PR-2、PR-5和Ta-JA2基因 表达以及小麦白粉病抗性的诱导

 为了探索小麦抗白粉病分子机理,明确茉莉酸对小麦白粉病抗性的诱导作用、对植物抗病性标志基因PR-1、PR-2、PR-5和本实验室克隆的1个新基因Ta-JA2的激活作用,以及抗病性变化与基因表达变化之间的相关性,本研究以感白粉病的小麦品种“中国春”、“濮麦9号” 和“周麦18”为材料,用茉莉酸甲酯（methyl jasmonate,MeJA）喷洒小麦幼苗叶片进行诱导,通过离体叶段培养法接种白粉菌（Blumeria graminis f. sp. tritici,Bgt）进行抗性鉴定;用实时定量PCR技术检测小麦叶片中PR-1、PR-2、PR-5和Ta-JA2基因的表达变化。结果表明MeJA处理可以显著提高“中国春”、“濮麦9号”和“周麦18”对白粉菌的抗病水平。茉莉酸处理显著激活了PR-1、PR-2、PR-5和Ta-JA2的转录。茉莉酸诱导的抗病性提高与抗病标志基因PR-1、PR-2、PR-5及Ta-JA2的表达增强呈正相关。植物激素茉莉酸是小麦抗白粉病反应的信号分子。     

帚枝霉属内生真菌激发子蛋白SbES诱导辣椒抗棒孢叶斑病作用机理

为明确帚枝霉属Sarocladium内生生防真菌HND5菌株外泌激发子蛋白SbES的诱导辣椒抗病作用机理,通过构建SbES蛋白的毕赤酵母Pichia pastoris重组蛋白表达菌株,利用纯化后的SbES重组蛋白处理辣椒植株,检测辣椒对棒孢叶斑病的抗性,以及相关抗病反应与抗病基因表达的变化。结果表明,0.1 mg/mL SbES重组蛋白可有效诱导辣椒产生对棒孢叶斑病的抗性,可激发辣椒叶片活性氧爆发、微过敏反应和胼胝质积累等抗病反应;并能有效提高辣椒叶片中与活性氧爆发、过敏性反应、胼胝质合成和植保素合成等抗病反应相关基因,以及水杨酸、茉莉酸和乙烯信号传导关键基因的表达。推测帚枝霉属内生真菌激发子蛋白SbES可通过激活多种抗病信号传导途径来激发辣椒产生对棒孢叶斑病的抗性。     

水杨酸和乙烯在烟草抗黑胫病中的作用

5mmol/L水杨酸或1g/L乙烯外源处理可诱导烟草对黑胫病的抗性，推迟植株死亡。不能积累水杨酸的转nahG基因植株和不表现乙烯应答反应的转etr1-1基因植株对黑胫病的抗性显著弱于野生型植株。组成性积累高水平水杨酸的转entC和pmsB基因植株对黑胫病的抗性明显强于野生型植株。这些结果说明水杨酸和乙烯增强烟草对黑胫病的抗性，减缓黑胫病的扩展。0．5mmol/L KCN连续浇灌植株4天或浸溃叶片2，4h均不能恢复转nahG基因植株丧失的对黑胫病的抗病性。此结果进一步支持关于KCN处理不能恢复转nahG基因植株丧失的对真菌病害抗病性的假说。     

Plant responses to plant growth-promoting rhizobacteria

Non-pathogenic soilborne microorganisms can promote plant growth, as well as suppress diseases. Plant growth promotion is taken to result from improved nutrient acquisition or hormonal stimulation. Disease suppression can occur through microbial antagonism or induction of resistance in the plant. Several rhizobacterial strains have been shown to act as plant growth-promoting bacteria through both stimulation of growth and induced systemic resistance (ISR), but it is not clear in how far both mechanisms are connected. Induced resistance is manifested as a reduction of the number of diseased plants or in disease severity upon subsequent infection by a pathogen. Such reduced disease susceptibility can be local or systemic, result from developmental or environmental factors and depend on multiple mechanisms. The spectrum of diseases to which PGPR-elicited ISR confers enhanced resistance overlaps partly with that of pathogen-induced systemic acquired resistance (SAR). Both ISR and SAR represent a state of enhanced basal resistance of the plant that depends on the signalling compounds jasmonic acid and salicylic acid, respectively, and pathogens are differentially sensitive to the resistances activated by each of these signalling pathways. Root-colonizing Pseudomonas bacteria have been shown to alter plant gene expression in roots and leaves to different extents, indicative of recognition of one or more bacterial determinants by specific plant receptors. Conversely, plants can alter root exudation and secrete compounds that interfere with quorum sensing (QS) regulation in the bacteria. Such two-way signalling resembles the interaction of root-nodulating Rhizobia with legumes and between mycorrhizal fungi and roots of the majority of plant species. Although ISR-eliciting rhizobacteria can induce typical early defence-related responses in cell suspensions, in plants they do not necessarily activate defence-related gene expression. Instead, they appear to act through priming of effective resistance mechanisms, as reflected by earlier and stronger defence reactions once infection occurs.     

Pseudomonas aeruginosa 7NSK2-induced Systemic Resistance in Tobacco Depends on in planta Salicylic Acid Accumulation but is not Associated with PR1a Expression

Root colonization by rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to systemic acquired resistance induced by a localized pathogen infection. We used the tobacco–tobacco mosaic virus model to investigate whether the systemic resistance induced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 is mediated by the systemic acquired resistance signal transduction pathway. Experiments with nahG-transformed tobacco revealed that Pseudomonas aeruginosa 7NSK2-induced resistance depended on in planta salicylic acid accumulation for its expression but not for its induction and is, in this respect, similar to systemic acquired resistance. However, Pseudomonas aeruginosa 7NSK2-induced resistance was, unlike systemic acquired resistance, not associated with PR1a expression at the time of challenge with tobacco mosaic virus. This suggests that Pseudomonas aeruginosa 7NSK2 treatment would only potentiate defense gene expression in systemic tissue, which would also explain why its level of resistance is lower than in case of systemic acquired resistance. Because we demonstrated that induced resistance by Pseudomonas aeruginosa 7NSK2 exclusively depends on the production of salicylic acid by this strain our conclusions might also account for other salicylic acid-producing and resistance-inducing rhizobacteria.     

内生细菌EBS05对烟草诱导抗性的信号转导途径研究

 樟树内生枯草芽胞杆菌EBS05是一株对多种植物病原菌具有较强拮抗活性,并能诱导烟草系统抗性的生防菌株。本文以缺失Surfactin A合成相关基因的突变菌株EBS05^T为材料,研究了内生细菌EBS05对烟草诱导系统抗性的激发子及其信号转导途径。结果表明,菌株EBS05产生的Surfactin A是诱导烟草对TMV系统抗性的有效激发子;Surfactin A诱导处理后,SA信号转导途径下游的关键调节基因NPR1首先被激活,并持续超量表达,进而触发PR1b和PR1a基因持续超量表达,表明Surfactin A诱导烟草对TMV的系统抗性是通过激活SA信号转导途径实现的。同时,Surfactin A诱导处理后24~72 h,JA/ET信号转导途径调节基因PDF1.2被激活,且超量表达,表明在Surfactin A诱导烟草对TMV系统抗性的信号转导过程中,可能存在SA信号途径和JA/ET信号途径的交叉协同作用。     

The Relationship Between Pathogen-induced Systemic Resistance (ISR) and Multigenic (horizontal) Resistance in Plants

Plants have developed mechanisms to successfully co-exist in the presence of pathogenic organisms. Some interactions between plants and pathogens are based on recognition of specific elicitor molecules from avirulent pathogen races (avr gene products), which is described in the gene-for-gene resistance theory. Another type of resistance, multigenic (horizontal) resistance, is a less well-studied phenomenon that depends upon multiple genes in the plant host. All plants possess resistance mechamisms which can be induced upon pre-treatment of plants with a variety of organisms or compounds. This general phenomenon is known as induced systemic resistance (ISR). At least in some plant species, ISR depends on the timely accumulation of multiple gene products, such as hydrolytic enzymes, peroxidases or other gene products related to plant defences. The pre-treatment of plants with an inducing organism or compound appears to incite the plant to mount an effective defense response upon subsequent encounters with pathogens, converting what would have been a compatible interaction to an incompatible one. Our studies in three plant–pathogen systems clearly document that multigenic-resistant plants constitutively express specific isozymes of hydrolytic enzymes that release cell wall elicitors, which in turn may activate other defense mechanisms. ISR induces constitutive accumulation of these and other gene products prior to challenge. ISR is known to function against multiple organisms, and there is no specificity observed in the accumulation patterns of defense-related gene products when ISR is induced. It is therefore hypothesized that the constitutive accumulation of specific isozymes of hydrolytic enzymes, or other defense related gene products, is an integral part of both multigenic resistance and the phenomenon of ISR. Further, plants in which ISR has been activated appear to move from a latent resistance state to one in which a multigenic, non-specific form of resistance is active.     

Staying alive – is cell death dispensable for plant disease resistance during the hypersensitive response?

Probably the most known and best studied type of plant resistance to pathogenic infections is the hypersensitive response (HR), a form of localized programmed cell death associated with restriction or killing of pathogens that often leads to macroscopically visible localized tissue necrosis. It is generally assumed that cell death and resistance within the HR are physiologically and genetically linked. However, there has been considerable speculation about whether cell death is an absolute requirement for resistance conditioned by the HR. This review discusses the relation of cell death and resistance in the HR, in particular, the importance of cell death in this process. We intend to focus on the increasing amount of research evidence showing that in several plant-pathogen interactions, the two main components of the HR – resistance and cell death – can be physiologically, genetically and temporally uncoupled. In other words, HR should be considered as a combination of resistance and cell death responses, where cell death may be dispensable for plant disease resistance. The varying contribution of these two components (i.e. cell death and resistance) generates an array of defense strategies differing in efficiency. Thus, a very early and rapid defense response seems to contribute to the development of macroscopically symptomless (extreme) resistance, while a moderately early defense response results in resistance with the concomitant development of controlled and limited cell and tissue death (HR). Accordingly, a delayed and failed attempt by the host to elicit resistance responses would result in massively stressed plant tissues (e.g. “systemic HR”) and a partial or almost complete loss of control over pathogen invasion. The dynamic nature of resistance responses in plants implies that resistance can be effective with or without cell death but its outcome and efficiency may depend primarily on the timing and speed of the host response.     

无致病性腐霉的生防作用和诱导防卫反应

寡雄腐霉Pythium oligandrum作为一种重要的土传病害生防因子越来越受到关注,它能在多种重要农作物根围定殖,对20多种病原真菌或其它卵菌具有拮抗或寄生作用,并能诱导植物产生防卫反应.寡雄腐霉产生的拟激发素寡雄蛋白诱导番茄系统获得抗性,抵抗寄生疫霉Phytophthora parasitica和尖孢镰刀菌羽扇豆-番茄枯萎病菌Fusarium oxysporum f.sp.radicis-lycopersici侵入,显著降低病害的发生率.作者对寡雄腐霉的分离与鉴定、寄主种类、寄生作用、抗生作用和拟激发素寡雄蛋白诱导番茄系统获得抗性等方面的研究进行了综述.     

Signal Interactions in Induced Resistance to Pathogens and Insect Herbivores

Plants are often simultaneously challenged by pathogens and insects capable of triggering an array of responses that may be beneficial or detrimental to the plant. The efficacy of resistance mechanisms can be strongly influenced by the mix of signals generated by biotic stress as well as abiotic stress such as drought, nutrient limitation or high soil salinity. An understanding of their biochemical nature, and knowledge of the specificity and compatibility of the signaling systems that regulate the expression of inducible responses could optimize the utilization of these responses in crop protection. Signaling conflicts and synergies occur during a plant's response to pathogens and insect herbivores, and much of the research on defense signaling has focused on salicylate- and jasmonate-mediated responses. We will review our results using tomato (Lycopersicon esculentum) in greenhouse and field studies that illustrate a trade-off between salicylate- and jasmonate-mediated signaling, and discuss research on strategies to minimize the trade-off that can occur following the application of chemical elicitors of resistance. In addition, there is evidence of another signaling system that mediates endogenous levels of ceramide in the plant. This signal is associated with programmed cell death and protection of tomato against the fungal pathogen Alternaria alternata f. sp. lycopersici.     

Systemic resistance to bacterial leaf speck pathogen in Arabidopsis thaliana induced by the culture filtrate of a plant growth-promoting fungus (PGPF) Phoma sp. GS8-1

The culture filtrate (CF) from the plant growth-promoting fungus Phoma sp. GS8-1 was found to induce systemic resistance in Arabidopsis thaliana against the bacterial leaf speck pathogen Pseudomonas syringae pv. tomato DC3000 (Pst), and the underlying mechanism was studied. Roots of A. thaliana were treated with CF from GS8-1, and plants expressed a clear resistance to subsequent Pst infection; disease severity was reduced, and proliferation of pathogen was suppressed. Various mutants of A. thaliana were used to test whether the CF induced resistance through one of the known signaling pathways: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The CF was fully protective against Pst in Arabidopsis mutants jar1 and ein2 similar to wild-type plants. However, its efficacy was reduced in plants containing transgene NahG. Examination of systemic gene expression revealed that CF modulates the expression of SA-inducible PR-1, PR-2 and PR-5 genes, the JA/ET-inducible ChitB gene, and the ET-inducible Hel gene. Moreover, the expression of these genes was further enhanced upon subsequent stimulation after attack by Pst. Our data suggest that in addition to a partial requirement for SA, the signals JA and ET may also play a role in defense signaling in Arabidopsis.