拟南芥的抗病信号传导途径

 拟南芥是研究植物与病原物相互作用的模式植物。植物感病和抗病取决于病原物无毒基因产物和寄主抗病基因产物的识别,以及随后的相关防卫反应的激活。在拟南芥的抗病过程中,水杨酸、茉莉酸、乙烯等信号分子都不同程度地参与着抗病过程中的不同环节,起着非常重要的作用。由于这些信号分子在对不同病原菌的抗性中的作用存在差异,因而将抗病信号传导分为依赖于水杨酸和依赖于茉莉酸/乙烯的途径。本文将着重讨论这些信号分子在植物系统获得抗性以及诱导系统抗性中的作用。     

AM真菌诱导的番茄信号物质及其对根结线虫的 抑制 效应

丛枝菌根(AM)真菌能诱导植物合成一些信号物质,如茉莉酸(JA)、水杨酸(SA)、一氧化氮(NO)、H2O2等,这些信号在AM真菌与植物识别、共生体建立和激活植物防御系统过程中发挥着重要作用[1].     

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.     

植物防御中茉莉酸信号通路抑制与终止的作用机制

茉莉酸（jasmonate,JA）作为重要的植物激素,在平衡植物生长发育和响应外界胁迫中发挥着重要作用。植物响应外界胁迫主要是通过激活信号转导通路实现信号传递的级联放大信号进而实现防御响应。然而,植物防御是一个高能耗过程,防御的适时抑制与终止有利于植物的生长发育。针对植物茉莉酸信号通路的抑制与终止研究,总结参与防御相关茉莉酸信号通路抑制与终止的主要调控因子,阐述茉莉酸ZIM结构域蛋白（jasmonate ZIM-domain,JAZ）、髓细胞组织增生蛋白2（myelocytomatosis 2,MYC2）、JA相关类MYC2蛋白（JA-associated MYC2-like,JAM）和MYC2直接调控bHLH蛋白（MYC2-targeted BHLH,MTB）等对茉莉酸信号通路进行抑制与终止的作用机制,总结抑制茉莉酸信号通路的茉莉酸代谢途径,最后对茉莉酸信号通路抑制与终止机制的研究方向进行展望。     

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。     

茉莉酸对害虫的控制作用研究进展

茉莉酸（JA）广泛存在于植物体中,是植物防御反应的一种重要信号分子。根据目前的研究对茉莉酸的合成途径、茉莉酸诱导的直接和间接防御反应以及外源茉莉酸处理对害虫的控制作用进行概括和总结,并对茉莉酸的应用前景进行展望。     

诱导抗性在果蔬采后病害防治中的研究与应用

 近年来,有关果蔬产品采后诱导抗性的研究较多,生物和非生物因子(如微生物、化学物质、物理因素以及天然物质等)都能够诱导果蔬产品采后的抗性。生物因子研究较多的是拮抗菌,许多生物拮抗菌都具有自生和诱导果实产生抗病相关酶活性的作用,可以有效抑制病原菌的生长。物理诱导主要包括γ-射线、离子辐射、紫外光照和热水处理等,热水浸泡柑橘果实能有效控制贮藏期间的腐烂;低剂量紫外光照射桃、芒果、草莓、葡萄和甜椒等果蔬产品可明显减轻采后病害。用于果蔬产品的化学诱导剂主要有β-氨基丁酸(BABA),苯丙噻重氮(ASM),水杨酸(SA),茉莉酸(JA)和茉莉酸甲酯(MJ)等。将SA与生物拮抗菌配合,可诱导甜樱桃果实过氧化物酶(POD),苯丙氨酸裂解酶(PAL)和β-1,3-葡聚糖酶的活性,提高果实贮藏期间的抗病性;ASM在开花前处理哈密瓜也具有一定的抗病诱导效果;用BABA处理葡萄柚后,能刺激果实伤口附近PAL活性增加,增强了果实对绿霉病菌侵染的抵抗力;作为植物生长调节剂的JA及其酯化物MJ,对植物抗病性也具有明显的诱导作用,JA和MJ被认为是植物在病原菌侵染防御反应中细胞信号转导的一种关键物质;用MJ处理采后的苹果和桃果实能增强贮藏期间的抗病性,其诱导强度与果实的成熟度密切相关;将钙盐与生物拮抗菌配合使用,也显著提高拮抗菌的抑病效果。另外,在自然抗病物质中壳聚糖的使用较多,用它处理柑橘果实可提高贮藏期间绿霉病的防治效果。这些生物和非生物因子的诱导抗性机理主要涉及到寄主的细胞结构变化和生理生化反应。本文较详细地论述了诱导果蔬产品采后抗性的因子及其可能的诱导机理。     

茉莉酸介导的丛枝菌根真菌诱导植物抗病性研究进展

丛枝菌根（arbuscular mycorrhizal,AM）真菌能与植物根系建立共生体提高植物抗病性。植物激素茉莉酸（jasmonic acid,JA）参与AM的形成,介导AM真菌诱导的植物抗病性。目前,关于AM真菌诱导的植物抗病性内容较为丰富,但是关于JA介导的AM真菌诱导的植物抗病性却有待进一步研究。本文首先总结了JA对AM形成和AM对植物内源JA积累的影响;其次介绍了AM真菌对植物抗病性影响及诱导机制;最后从诱导形成防御结构、提高酶活性及合成防御蛋白、诱导次生代谢物质合成、诱导调控信号分子、JA与其他激素相互作用五个方面探讨了JA在AM真菌诱导抗病性中的作用,并对本领域的研究方向进行展望,以期为植物病害防治和菌根研究提供可借鉴的思路。     

沉默转录因子OsERF7提高水稻对褐飞虱和白背飞虱的抗性

为了解植物中特有的转录因子乙烯响应因子(ethylene responsive factor,ERF)在植物诱导抗虫反应中的作用,通过克隆1个水稻ERF转录因子基因OsERF7,并结合分子生物学、反向遗传学及生物测定,探究其在水稻防御褐飞虱Nilaparvata lugens和白背飞虱Sogatella furcifera为害过程中的作用。结果显示,机械损伤处理与褐飞虱产卵雌成虫为害均能在中后期诱导OsERF7的表达。沉默OsERF7能显著降低水稻上褐飞虱及白背飞虱卵的孵化率,并延长褐飞虱卵的发育历期;与野生型水稻相比,褐飞虱和白背飞虱在沉默突变体品系R1和R30上的卵孵化率分别只有野生型水稻上的62.5%～68.3%和68.0%～76.0%,褐飞虱卵的发育历期则延长0.37～0.45 d。沉默OsERF7不影响褐飞虱产卵雌成虫为害诱导的水稻防御相关信号分子—茉莉酸(JA)、水杨酸(SA)、乙烯(ET)和过氧化氢(H_2O_2)的含量。表明转录因子OsERF7作用于防御相关信号途径的下游,并且负调控水稻对褐飞虱和白背飞虱的抗性。     

防御相关激素与纹枯病菌处理下水稻VQ基因家族的转录分析

 VQ蛋白与WRKY转录因子互作,调节植物防御反应。本研究分析了水稻VQ基因家族在水杨酸(SA)、茉莉酸(JA)、乙烯(ET) 3种防御相关激素和纹枯病菌(Rhizoctonia solani)处理下的转录表达谱。结果表明,水稻VQ基因家族有1/3以上成员至少响应一种处理,OsVQ2、-11和-35的表达在3种激素处理下均显著上调,其中OsVQ2的表达还受R. solani显著诱导。特别是,OsVQ2、-35、-34、和-37分别在SA、JA、ET和R. solani处理下诱导最为明显。启动子顺式元件分析表明,包括W-box核心序列在内的病原响应元件和叶肉组织表达元件CACTFTPPCA1在响应R. solani的VQ基因启动子区域富集,与R. solani侵染下的VQ基因表达特征和纹枯病危害寄主的组织特征基本符合。这些发现提示部分水稻VQ基因可能通过SA、JA或ET信号途径参与了对纹枯病的防御反应,为解析基因功能指明了方向。     

Rhizobacteria-mediated Induced Systemic Resistance: Triggering, Signalling and Expression

Selected strains of rhizosphere bacteria reduce disease by activating a resistance mechanism in the plant named rhizobacteria-mediated induced systemic resistance (ISR). Rhizobacteria-mediated ISR resembles pathogen-induced systemic acquired resistance (SAR) in that both types of induced resistance render uninfected plant parts more resistant towards a broad spectrum of plant pathogens. Some rhizobacteria trigger the salicylic acid (SA)-dependent SAR pathway by producing SA at the root surface. In other cases, rhizobacteria trigger a different signalling pathway that does not require SA. The existence of a SA-independent ISR pathway has been demonstrated in Arabidopsis thaliana. In contrast to pathogen-induced SAR, ISR induced by Pseudomonas fluorescens WCS417r is independent of SA accumulation and pathogenesis-related (PR) gene activation but, instead, requires responsiveness to the plant hormones jasmonic acid (JA) and ethylene. Mutant analyses showed that ISR follows a novel signalling pathway in which components from the JA and ethylene response are successively engaged to trigger a defensive state that, like SAR, is controlled by the regulatory factor NPR1. Interestingly, simultaneous activation of both the JA/ethylene-dependent ISR pathway and the SA-dependent SAR pathway results in an enhanced level of protection. Thus combining both types of induced resistance provides an attractive tool for the improvement of disease control. This review focuses on the current status of our research on triggering, signalling, and expression of rhizobacteria-mediated ISR in Arabidopsis.     

Costs and trade-offs associated with induced resistance

Plants resist attack by pathogens and herbivorous insects through constitutive and inducible defences. Based on differences in signalling pathways and spectra of effectiveness, different types of induced resistance have been defined. Systemic acquired resistance (SAR) occurs in distal plant parts following localized infection by a necrotizing pathogen. It is controlled by a signalling pathway that depends upon the accumulation of salicylic acid (SA) and the regulatory protein NPR1. In contrast, induced systemic resistance (ISR) is induced by selected strains of non-pathogenic plant growth promoting bacteria (PGPR). ISR functions independently of SA, but requires NPR1 and is regulated by jasmonic acid (JA) and ethylene (ET). It is generally believed that induced resistance evolved to save energy under pathogen or insect-free conditions, although costs still arise when defences are activated following attack. Costs can arise from the allocation of resources to defence and away from plant growth and development, and there are also ecological costs which result from trade-offs between induced resistance and the plant's interaction with beneficial organisms e.g. mycorrhizal fungi. To date, few studies have examined the costs and trade-offs associated with induced resistance to pathogens. There is a clear need for long-term studies of costs and trade-offs associated with induced resistance in crops under commercial conditions. Without such information, the potential offered by induced resistance is unlikely to be realized.     

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     

Role of methyl jasmonate in the expression of mycorrhizal induced resistance against Fusarium oxysporum in tomato plants

Arbuscular mycorrhiza (AM) colonization led to a decrease in the severity of fusarium wilt disease caused by Fusarium oxysporum f. sp. lycopersici in tomato plants. The involvement of two plant defense hormones, namely methyl jasmonate (MeJA) and salicylic acid (SA), in the expression of mycorrhiza induced resistance (MIR) against this vascular pathogen was studied in the AM colonized and non-colonized (controls) plants. Activity of lipoxygenase (LOX), which plays a role in jasmonic acid (JA) biosynthesis, as well as levels of methyl jasmonate (MeJA) increased in AM colonized plants as compared to controls, but did not show any further changes in response to F. oxysporum inoculation. On the other hand, activity of phenylalanine ammonia lyase (PAL), which is an enzyme from salicylic acid (SA) biosynthetic pathway, as well as SA levels, increased in both controls and AM colonized plants in response to application of F. oxysporum spores. Hence the JA and not the SA signalling pathway appeared to play a role in the expression of MIR against this vascular pathogen. The resistance observed in AM colonized plants was completely compromised when plants were treated with the JA biosynthesis inhibitor salicylhydroxamic acid (SHAM). This confirmed that the AM-induced increase in JA levels was involved in the expression of resistance toward F. oxysporum. The SA response gene pathogenesis-related 1 (PR1) showed an increased expression in response to F. oxysporum infection in SHAM treated AM colonized plants as compared to plants that were not treated with this JA inhibitor. This suggested the possibility that JA inhibited SA responses, at least in the roots. AM colonization therefore appeared to prime plants for improved tolerance against the vascular pathogen F. oxysporum, which was mediated through the JA signalling pathway.     

Suppressive effect of abscisic acid on systemic acquired resistance in tobacco plants

Recent studies have indicated that the phytohormone abscisic acid (ABA), induced in response to a variety of environmental stresses, plays an important role in modulating diverse plant–pathogen interactions. In Arabidopsis thaliana, we previously clarified that ABA suppressed the induction of systemic acquired resistance (SAR), a plant defense system induced by pathogen infection through salicylic acid (SA) accumulation. We investigated the generality of this suppressive effect by ABA on SAR using tobacco plants. For SAR induction, we used 1,2-benzisothiazole-3(2H)-one 1,1-dioxide (BIT) and benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) that activate upstream and downstream of SA in the SAR signaling pathway, respectively. Wild-type tobacco plants treated with BIT or BTH exhibited enhanced disease resistance against Tobacco mosaic virus (TMV) and tobacco wildfire bacterium, Pseudomonas syringae pv. tabaci (Pst), however, which was suppressed by pretreatment of plants with ABA. Pretreatment with ABA also suppressed the expression of SAR-marker genes by BIT and BTH, indicating that ABA suppressed the induction of SAR. ABA suppressed BTH-induced disease resistance and pathogenesis-related (PR) gene expression in NahG-transgenic plants that are unable to accumulate SA. The accumulation of SA in wild-type plants after BIT treatment was also suppressed by pretreatment with ABA. These data suggest that ABA suppresses both upstream and downstream of SA in the SAR signaling pathway in tobacco.     

Investigating interactions of salicylic acid and jasmonic acid signaling pathways in monocots wheat

Upon pathogen or insect attack, plants respond with production of a specific blend of the alarm signals salicylic acid (SA) and jasmonic acid (JA), which are recognized as key players in the regulation of the signaling pathways involved. SA and JA responsive genes and SA/JA cross talk were well characterized in dicotyledonous species, but little is known in monocotyledonous plants. Using qRT-PCR, the expression profiles of SA and JA responsive genes were investigated after SA and JA treatments in monocots wheat. The results showed that Glu2 and PR-2 responded almost exclusively to SA, PR-3 and LOX2 responded positively to methyljasmonate (MeJA) treatment, while Lipase and PR-1.1 were induced in response to treatment with SA or MeJA. Furthermore, either by pathogen infection or exogenous application of hormones can activate the antagonistic effect between SA and JA in wheat, which has been well elucidated in dicotyledonous species. The outcomes of SA-JA interactions could be affected by the relative concentration of each hormone. This study shed light on marker genes that can represent SA and JA pathways in wheat and provided some clues for better understanding their interactions in monocot.     

Induced resistance in tomato plants to the toxin-dependent necrotrophic pathogen Alternaria alternata

A necrotrophic pathogen, the tomato pathotype of Alternaria alternata (Aa) causes Alternaria stem canker on tomato. Its pathogenicity depends on the production of host-specific AAL-toxin. Pre-inoculation with nonpathogenic Aa or pretreatment an elicitor prepared from Aa reduced disease symptoms by the pathogen. Salicylic acid (SA)- and jasmonic acid (JA)-dependent defense responses in tomato are not involved in the resistance to the pathogen induced by nonpathogenic Aa. The results suggest that an alternative and unknown signaling pathway independent of SA- and JA-signaling might modulate the induced resistance by activating the expression of the multiple defense genes.     

Antagonism between acibenzolar-S-methyl-induced systemic acquired resistance and jasmonic acid-induced systemic acquired susceptibility to Colletotrichum orbiculare infection in cucumber

In cucumber, we show salicylic acid only induce local acquired resistance (LAR), whereas acibenzolar-S-methyl (ASM) can induce LAR and systemic acquired resistance (SAR) to plant diseases. Jasmonic acid (JA) can induce local acquired susceptibility (LAS) and systemic acquired susceptibility (SAS). ASM treatment of lower first leaves leads to the accumulation of cucumber acidic class III chitinase (CHI2) in untreated upper leaves and effectively suppresses lesion formation on those leaves. In contrast, JA treatment completely suppresses CHI2 gene expression and causes plants to be more susceptible to Colletotrichum orbiculare. ASM-induced SAR can effectively antagonize the JA-induced SAS, providing a response that is midway between what would be expected with either JA or ASM by themselves.     

Jasmonic and salicylic acid-induced resistance in sorghum against the stem borer Chilo partellus

Induced resistance was studied in three sorghum genotypes (IS2205, ICSV1 and ICSV700) against Chilo partellus (Swinhoe) (Lepidoptera; Pyralidae) infestation and jasmonic acid (JA) and salicylic acid (SA) application. The activity of plant defensive enzymes [peroxidase (POD), polyphenol oxidase (PPO), superoxide dismutase (SOD), and catalase (CAT)], and the amounts of total phenols, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and proteins were recorded at 6 days after infestation. The induction of enzyme activities and the amounts of secondary metabolites varied among the genotypes and treatments. The genotype IS2205 showed a stronger effect than that of ICSV1 or ICSV 700. Treatment with JA followed by insect infestation induced greater levels of enzymes and secondary metabolites. The results suggest that JA induces greater levels of resistance components in sorghum plants against insect pests. Thus, pretreatment of plants with elicitors including JA and SA could provide a greater opportunity for plant defense against herbivores.