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1.
Sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum (Lib.) De Bary is a serious fungal disease of soybean. Senescing petals provide a starting nutrient source for the invasion of healthy tissue by the advancing oxalic acid secreting fungal hyphae. Since oxalic acid is a major pathogenicity factor of SSR, transgenic soybean capable of degrading oxalic acid may be resistant to the pathogen. Transgenic soybean plants were produced byAgrobacterium -mediated transformation with the wheat germin gene (gf-2.8) encoding an oligomeric protein, oxalate oxidase (OxO), which oxidizes oxalic acid to carbon dioxide and hydrogen peroxide (H2O2). Transgenic soybean homozygous for 35S- gf-2.8 produced an approx. 130 kDa protein indistinguishable from wheat germin, and with OxO activity. OxO activity was prominent in cell walls proximal to the site of pathogen attack. The transgenics had greatly reduced disease progression and lesion length following cotyledon and stem inoculation with S. sclerotiorum indicating that the germin gene product conferred resistance to SSR. This is the first report of plant resistance to the fungal pathogen S. sclerotiorum in transgenic plants expressing OxO.  相似文献   

2.
We have previously shown that flagellin of Pseudomonas syringae pv. tabaci is an elicitor that induces a hypersensitive reaction (HR) in nonhost tomato cells. Flagellin is the major HR elicitor produced by this pathogen, as shown by the inability of a flagellin-defective mutant, ΔfliC, to induce HR. Also, a ΔfliD mutant that secretes large amounts of monomer flagellins induces a strong HR in tomato. In this study, the possible involvement of an Hrp type III secretion system (TTSS) in flagellin-induced HR was investigated using flagella-defective mutants or Hrp TTSS-defective mutants. The hrcC gene encodes HrcC protein, which is required for Hrp pilus formation in the outer membrane. An hrcC mutation, introduced into the wild-type, ΔfliC, and ΔfliD mutants of P. syringae pv. tabaci did not affect swimming motility or flagellin secretion, whereas all ΔhrcC, ΔfliC, and ΔfliD mutants lost the ability to cause disease on host tobacco leaves. However, the ΔhrcC mutant and the ΔfliD/ΔhrcC double mutant were still able to induce HR cell death, expression of one of the defense-related genes hsr203J, and the generation of hydrogen peroxide in nonhost tomato cells. Thus, flagellin is required for both pathogenicity in host tobacco and HR in nonhost tomato. On the other hand, hrp TTSS is necessary for pathogenicity on host tobacco but is not indispensable to induce HR in nonhost tomato. These results clearly show that flagellin-induced HR is hrp-independent in tomato.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB049570  相似文献   

3.
采用盆栽试验,研究了干旱胁迫对野生及栽培大豆生理特性及抗氧化酶活性的影响。即用相对含水量分别为80%、70%、60%、50%、40%、30%的土壤分别栽种野生大豆和栽培大豆,测定其根系活力、细胞膜透性、超氧化物歧化酶（SOD）活性、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性及丙二醛（MDA）含量。结果表明：在同样的土壤相对含水量以及干旱胁迫程度下,相对于栽培大豆,野生大豆表现出高根系活力和抗氧化酶活性以及低细胞膜透性和丙二醛含量。由此可以说明野生大豆的抗干旱能力高于栽培大豆。  相似文献   

4.
Soybean (Glycine max (L.) Merill, cv. Williams 82) plants and cell cultures respond to avirulent pathogens with a hypersensitive reaction. After inoculation of soybean with Pseudomonas syringae pv. glycinea, carrying the avirulence gene avrA, or zoospores from the fungus Phytophthora sojae Race 1, a resistance-gene-dependent cell death programme is activated. A new gene was identified by differential display of mRNAs that is specifically activated during the early phase of incompatible pathogen-soybean interactions but does not respond to compatible pathogens. The gene is strongly induced within 2h after addition of P. sojae zoospores. A similar kinetic pattern was observed for P. syringae (avrA) inoculated soybean cell cultures. The gene encodes a deduced protein of 368 amino acids with a very high content of asparagine and was therefore termed N-rich protein (NRP). The protein is composed of two distinct domains, of which only the C-terminal domain has striking homology to proteins of unknown function from other plants. An antibody raised against the recombinant NRP recognizes a protein of 42kDa. The protein is located in the cell wall as indicated by cell fractionation studies. Comparison of the genomic DNA-sequence with the cDNA, identified two introns within the open reading frame. The NRP-gene is not directly induced by salicylic acid or hydrogen peroxide, indicating a distinct and specific signal transduction pathway which is only activated during programmed cell death. The NRP-gene appears to be a new marker in soybean activated early in plant disease resistance.  相似文献   

5.
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6.
The Phytophthora-derived oligopeptide elicitor, Pep-13, originally identified as an inducer of plant defense in the nonhost–pathogen interaction of parsley and Phytophthora sojae, triggers defense responses in potato. In cultured potato cells, Pep-13 treatment results in an oxidative burst and activation of defense genes. Infiltration of Pep-13 into leaves of potato plants induces the accumulation of hydrogen peroxide, defense gene expression and the accumulation of jasmonic and salicylic acids. Derivatives of Pep-13 show similar elicitor activity in parsley and potato, suggesting a receptor-mediated induction of defense response in potato similar to that observed in parsley. However, unlike in parsley, infiltration of Pep-13 into leaves leads to the development of hypersensitive response-like cell death in potato. Interestingly, Pep-13-induced necrosis formation, hydrogen peroxide formation and accumulation of jasmonic acid, but not activation of a subset of defense genes, is dependent on salicylic acid, as shown by infiltration of Pep-13 into leaves of potato plants unable to accumulate salicylic acid. Thus, in a host plant of Phytophthora infestans, Pep-13 is able to elicit salicylic acid-dependent and -independent defense responses.  相似文献   

7.
The flagellins purified from Pseudomonas syringae pv. tabaci induce a hypersensitive reaction in nonhost tomato cells. To investigate the role of flagella and flagellin in the compatible interaction, we generated two types of flagella-defective mutant. The fliC mutant lost the fliC gene that encodes flagellin protein, whereas the fliD mutant lost the fliD gene that encodes HAP2-capping protein. The two mutants had markedly reduced ability to cause disease symptoms in tobacco leaves. Furthermore, propagation of the mutants in tobacco leaves was less than that in wild-type pv. tabaci. Compared to the inoculation with wild-type pv. tabaci, inoculation with the two mutants did not markedly induce the expression of typical defense response-related genes such as PAL and hsr203J. Complementation of each fliC and fliD gene to the corresponding deficient mutant restored motility and virulence. These results indicate that flagella of P. syringae pv. tabaci are indispensable organelles for complete virulence on host tobacco plants.  相似文献   

8.
为阐明燕麦嗜酸菌(Acidovorax avenae subsp.avenae,Aaa)鞭毛素蛋白Fli Caaa及其结构域对水稻免疫反应的诱导作用,通过分子生物学和生物信息学方法,对Aaa菌株IPN1的鞭毛素进行基因克隆及其序列分析;在大肠杆菌中对该基因全长、N端和C端片段进行了原核表达,纯化了Fli Caaa蛋白及其截短肽段;采用水稻叶片浸润法测定了表达蛋白对水稻免疫反应的诱导活性。结果表明,通过特异性引物的PCR扩增,获得1 479 bp的鞭毛素基因fli Caaa,其编码产物含有492个氨基酸,分子量为49.4 k D,具有flagellin-N和-C两个保守结构域;原核诱导表达获得了Fli Caaa、Fli Caaa-N和Fli Caaa-C可溶性融合蛋白;3种纯化蛋白均能诱导水稻细胞死亡和H2O2产生等免疫反应,但诱导能力略有差异。  相似文献   

9.
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10.
Treatment of tobacco with a mixture containing reactive oxygen species (ROS) and salicylic acid (SA) provided greater protection of tobacco against infection by Pseudomonas syringae pv. tabaci than either treatment alone. Synergism in expression from the promoter of the defense gene PR-1a was also observed. Although the ROS hydrogen peroxide and peracetic acid were poor inducers alone, they enhanced the level of -glucuronidase (GUS) activity expressed from the PR-1a promoter when applied with SA to a transgenic plant bearing a PR-1a::GUS fusion. PR-1a expression was not correlated with increased cell death as determined by Evans blue staining. There was no effect on the timing at which expression was increased by the mixture compared with the separate treatments. The mixture of hydrogen peroxide and SA partially mimicked the effect of a commercial product Oxycom that has field efficacy in improving plant performance. Repetitive applications of Oxycom enhanced expression from the PR-1a promoter and the production of the PR-1 protein. Enhanced activity occurred systemically both from aerial applications to single leaves and from root drenches. Root application strongly promoted veinal expression for the PR-1a promoter compared with confluent production in leaves of sprayed seedlings. Application methods and timing may aid in the success of activators of systemic acquired resistance in field conditions.  相似文献   

11.
Phaeomoniella chlamydospora (Pch) and Togninia minima (Tmi) produced scytalone, isosclerone and pullulans in liquid cultures, as well as in calli. Secondary metabolites and host defense compounds were shown to occur in calli of Vitis vinifera cv. Italia and cv. Matilde infected by the esca-associated fungi Pch, Tmi and Fomitiporia mediterranea (Fme). Calli of both cvs. were grown as dual cultures with Pch, Tmi and Fme. The fungi grew well in the presence of calli of both cvs., but callus growth was reduced. Accumulation and changes of total phenolics and recurring phenolics, and of two phytotoxic pentaketides and pullulans were analyzed by HPLC. On comparing results for cv. Italia and cv. Matilde, it can be seen that concentrations of phenolics are strongly related to the cv. The paper discusses the possible relationship between melanin biosynthesis in Pch and Tmi, which utilize pentaketide metabolites as intermediates and their pathogenicity related to phytotoxity of scytalone and isosclerone.  相似文献   

12.
Rhizoctonia solani AG-1 IA causes leaf blight on soybean and rice. Despite the fact that R. solani AG-1 IA is a major pathogen affecting soybean and rice in Brazil and elsewhere in the world, little information is available on its genetic diversity and evolution. This study was an attempt to reveal the origin, and the patterns of movement and amplification of epidemiologically significant genotypes of R. solani AG-1 IA from soybean and rice in Brazil. For inferring intraspecific evolution of R. solani AG-1 IA sampled from soybean and rice, networks of ITS-5.8S rDNA sequencing haplotypes were built using the statistical parsimony algorithm from Clement et al. (2000) Molecular Ecology 9: 1657–1660. Higher haplotype diversity (Nei M 1987, Molecular Evolutionary Genetics Columbia University Press, New york: 512p.) was observed for the Brazilian soybean sample of R. solani AG-1 IA (0.827) in comparison with the rest of the world sample (0.431). Within the south-central American clade (3-2), four haplotypes of R. solani AG-1 IA from Mato Grosso, one from Tocantins, one from Maranhão, and one from Cuba occupied the tips of the network, indicating recent origin. The putative ancestral haplotypes had probably originated either from Mato Grosso or Maranhão States. While 16 distinct haplotypes were found in a sample of 32 soybean isolates of the pathogen, the entire rice sample (n=20) was represented by a single haplotype (haplotype 5), with a worldwide distribution. The results from nested-cladistic analysis indicated restricted gene flow with isolation by distance (or restricted dispersal by distance in nonsexual species) for the south-central American clade (3-2), mainly composed by soybean haplotypes.  相似文献   

13.
Nine isolates of Phtophthora nicotianae were isolated from infected pepper plants. Their pathogenicity was studied in Capsicum annuum in comparison with P. nicotianae isolates from tomato and tobacco. The pathogenicity test showed that pepper isolates of P. nicotianae are adapted to their host. Banding patterns obtained by RAPD analysis with six oligonucleotide primers revealed polymorphism that grouped the isolates independently of the plant host. The polygenic dendrogram showed that pepper isolates were more similar to tomato isolates than to tobacco isolates. The RAPD bands of 1300 and 1500 bp, detected with primers OPD-01 and OPD-10, respectively, appeared specific to the most pathogenic pepper isolates. The OPK-08-1950 seems specific to the isolates of P. nicotianae from tomato. These results suggest that host specified might occur in P. nicotianae and that may be due to interspecific hybridization events resulting in novel pathogenic behavior.  相似文献   

14.
Plants sprayed with harpin, a bacterial protein that induces hypersensitive cell death (HCD), develop systemic acquired resistance (SAR) without macroscopic necrosis. HCD sometimes accompanies the development of resistance conferred by resistance (R) genes. In Arabidopsis, some R genes require one or both of the signalling components NDR1 and EDS1 for function. This study addresses whether HCD, NDR1 and EDS1 are required for induction of SAR by harpin. When Arabidopsis and tobacco leaves were sprayed with harpin, microscopic hypersensitive response (micro-HR) lesions developed. Systemic expression of PR genes and the development of resistance were accompanied by micro-HR, except in the ndr1-1 mutant, in which harpin induced micro-HR without the development of resistance or expression of the PR-1 gene. Cell death and resistance did not occur following treatment with harpin in plants that could not accumulate salicylic acid. Harpin also failed to induce resistance in Arabidopsis eds1-1 mutants. Therefore, harpin-induced resistance seems to develop concomitantly with cell death and resistance requires NDR1 and EDS1.  相似文献   

15.
The plasmid pUFZ75 conferred constitutive GFP expression on the bacterial pathogen Xanthomonas euvesicatoria (syn. X. campestris pv. vesicatoria). Colonisation of the tomato phyllosphere and invasion of tomato leaves by X. euvesicatoria was examined using both fluorescence and confocal laser scanning microscopy. Xanthomonas euvesicatoria established a limited population on the tomato leaf surface, primarily occupying the depressions between epidermal cells and around the stomata, prior to invasion of the leaf via the stomata and subsequent growth within the substomatal chamber and the leaf apoplast. Additionally, hrp-gfp fusions were used to report on the temporal and spatial expression of hrp genes during epiphytic colonisation and invasion. Xanthomonas euvesicatoria cells carrying hrpG- and hrpX-gfp reporter constructs were not fluorescent in vitro on non-hrp-inducing LB agar but did exhibit a low level of fluorescence on the leaf surface within 24 h of inoculation, particularly in the vicinity of stomata. Cells carrying hrpG- and hrpX-gfp fusions exhibited high levels of fluorescence 72 h after inoculation in the substomatal chamber and the leaf apoplast. Cells carrying the hrpF-gfp fusion were slightly fluorescent on LB agar and showed no further increase in fluorescence on the leaf surface by 24 h after inoculation, but did show a significant increase in fluorescence 72 h after inoculation in the substomatal chamber and apoplast. The apparent low-level induction of the regulators hrpG and hrpX on the tomato leaf surface may suggest that some of the genes of the X. euvesicatoria HrpG/HrpX regulon are up- or down-regulated prior to invasion of the stomata while still on the leaf surface.  相似文献   

16.
Using ELISA to determine whether cowpea mild mottle virus (CMMV) was present in soybean and groundnut seeds, the virus was not detected in 4144 seeds harvested from seven CMMV-infected soybean genotypes and in 214 seeds collected from CMMV-infected groundnut plants (cv. Gajah). These results, together with those of other researchers, suggest that, under the conditions tested, CMMV is not transmitted by seed. This in contrast to what is generally accepted and published in reviews.  相似文献   

17.
为明确毁灭炭疽菌Colletotrichum destructivum诱抗蛋白诱导烟草的抗病性及其作用,采用喷雾、摩擦接种方法及RT-PCR技术研究了诱抗蛋白的预防保护作用,以及烟草悬浮细胞经诱导后过氧化物酶(POD)、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)活性及脯氨酸(Pro)含量和病程相关基因表达的变化。结果表明,接种3、5和7 d后,该诱抗蛋白对烟草炭疽病的诱抗效果分别为58.00%、48.99%和49.65%,对烟草白粉病的诱抗效果分别为83.26%、80.76%和78.60%,并可以抑制烟草普通花叶病毒的复制及在寄主体内的扩增;经诱抗蛋白处理后,烟草悬浮细胞POD、PPO、PAL活性及Pro含量明显提高;诱抗蛋白能够诱导烟草病程相关蛋白基因PR-1a、PR-1b以及抗病信号传导途径关键基因NPR1的表达。表明毁灭炭疽菌诱抗蛋白可诱导烟草产生抗病性,可能与烟草悬浮细胞中POD、PAL、PPO的活性及Pro的含量提高以及相关病程基因表达有关。  相似文献   

18.
Secondary metabolites and host defense compounds were shown to occur in xylem sap, and leaves of Vitis vinifera cv. Italia and cv. Matilde naturally infected by the esca-associated fungi Phaeomoniella chlamydospora (Pch), Togninia minima (Tmi) and Fomitiporia mediterranea (Fme). Samples of xylem sap and leaves were collected from healthy vines and from vines showing severe symptoms of brown wood-streaking caused by Pch and Tmi, or from vines with symptoms of both brown wood-streaking and white rot caused by Fme. Xylem sap collection was carried out during the early spring of 2003 and 2004, corresponding to the phenological phases: (A) cotton bud; (B) green tip; (C) leaves out; (D) stretched out leaves; and (E) visible clusters. In the present work we have studied the accumulation of biomolecules (pentaketides and α-glucans), host defense compounds (benzaldehydes, benzoic acid and cinnamic acid derivatives, flavonols, flavanols, flavan-3-ol derivatives and stilbenes) at different stages of grapevine development. Accumulation and changes in total phenolics and recurring phenolics, and of three phytotoxic secondary metabolites (scytalone, isosclerone and pullulan) were analyzed by HPLC. On comparing results for cv. Italia and cv. Matilde, it can be seen that phenolic concentrations are strongly related to the cv.  相似文献   

19.
张媛  王芳  赵紫华 《植物保护学报》2023,50(5):1227-1236
昆虫病原线虫是一类专性侵染和寄生昆虫的病原线虫,是非常重要的生防资源。斯氏线虫属Steinernema和致病杆菌属Xenorhabdus通过形成共生体在侵染昆虫过程中共同完成生活史,其中致病杆菌释放效应物质引发昆虫败血症是其重要机制。该文对斯氏线虫-致病杆菌共生体的侵染策略和在侵染过程中产生的免疫调节因子、释放的毒素蛋白和活性代谢物进行概述,其中,苯乙酰胺作为免疫抑制因子促进自身定殖,脂多糖作为内毒素引起寄主血细胞裂解,Tc毒素蛋白作为外毒素导致寄主中肠上皮细胞溶解,活性代谢产物如xenematides、fabclavine和PAX肽等具有抑菌、诱导细胞凋亡等活性。而斯氏线虫本身也能够产生表皮/分泌蛋白来抑制寄主免疫,与共生菌协同致死寄主。因此,通过对斯氏线虫-致病杆菌共生体产生的致病物质进行汇总分析,为研究昆虫病原线虫致病机制提供理论参考,同时也为新型绿色杀虫剂的开发和应用提供证据支持。  相似文献   

20.
The viable but nonculturable (VBNC) state is induced in stress-injured bacterial cells. VBNC cells lose their ability to grow on standard media, but some of the cells can recover on media supplemented with H2O2-degrading compounds such as sodium pyruvate (SP). Here, VBNC cells that can recover on such media are called SP-recoverable VBNC cells; VBNC cells that do not recover are called SP-unrecoverable VBNC cells. On the basis of previous findings, we hypothesized that cells of Ralstonia solanacearum in which low temperature had induced the SP-recoverable VBNC state would regain their ability to grow on standard solid media after exposure to moderate temperature. To test this, cell suspensions of R. solanacearum were incubated at 5°C. When SP-recoverable VBNC cells were the only culturable cells present, the cell suspensions were exposed to 25°C. The temperature upshift caused an initial rapid increase in the number of active cells able to grow on standard solid media, followed by a more gradual increase. Linear regression analyses suggested that this increase was not attributable to the regrowth of a low level of residual active cells. In addition, all the revived cells tested caused wilt symptoms in susceptible tomato plants. When SP-unrecoverable VBNC cells were the only viable cells present in the 5°C microcosms, the cell suspensions were exposed to 25°C. In this case, no culturable cells were detected. Therefore, these data strongly suggest that the SP-recoverable VBNC cells regained their ability to grow on standard solid media after the temperature upshift and that the revived cells were virulent.  相似文献   

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