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1.
Certain phosphate salts are known inducers of systemic acquired resistance (SAR). In the present study, a local spray application of dipotassium hydrogenphosphate (K2HPO4) was effective in inducing a high level of systemic protection in cucumber plants against anthracnose caused by Colletotrichum lagenarium. Resistance induction by K2HPO4 was associated with localized cell death in cucumber leaves treated with the phosphate salt. The cell death observed, subsequently resulted in the appearance of macroscopically visible, necrotic spots. Appearing lesions resembled those provoked by tobacco necrosis virus (TNV) during a hypersensitive response (HR) that leads to pathogen-induced activation of SAR. Phosphate-mediated cell death was preceeded by a rapid generation of superoxide and hydrogen peroxide. As a further consequence of phosphate application, a local and systemic increase in free and conjugated salicylic acid (SA) levels was detected. The phosphate-induced responses were also identified with a similar time range in cucumber leaves that had been pre-inoculated with TNV. In contrast, none of these responses was triggered by application of the commercial plant activator benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester (BTH), which nevertheless was highly effective in inducing SAR in cucumber against anthracnose. In conclusion, the chemical SAR inducer K2HPO4 and the biological inducer TNV share some common early steps in signal transduction leading to SAR in cucumber, which differ from those involved in BTH-mediated SAR.  相似文献   

2.
When cowpea mesophyll tissue with or without any epidermal layer was inoculated with tobacco necrosis virus (TNV), local necrotic lesions were produced. In epidermal strips isolated after inoculation of intact leaves local lesions were never observed. Homogenates of epidermal strips removed within 30 min after inoculation of the leaf with the cowpea strain of tobacco mosaic virus (Cp-TMV) or with TNV and incubated on agar for 2 or 4 days were not infectious. However, when clusters of mesophyll cells or vein pieces were still attached to the epidermal strips after stripping, the homogenates showed virus activity. When cowpea leaves were inoculated with Cp-TMV or a common strain of TMV (TMV-U) infective virus material was present in the mesophyll tissue as measured in the homogenates, at the moment of stripping, i.e. within 10 min after inculation.It may be concluded that cowpea mesophyll cells can act as primary sites of viral ingress into the leaf and that the epidermis is not required for necrosis production after virus inoculation.Samenvatting De mogelijkheid werd onderzocht om cowpea-mesofylcellen zonder de aanwezigheid van epidermiscellen met TNV te infecteren. Kleine lokale necrotische lesies werden 40–72 uur na inoculatie zichtbaar waaruit blijkt, dat bij cowpea de epidermis niet noodzakelijk is voor de vorming van TNV-lesies. Geïsoleerd epidermisweefsel vertoonde nooit lokale lesies. Homogenaten van met TNV geïnoculeerde en daarna geïsoleerde cowpea-epidermisstukjes werden getoetst op virusactivitiet. Als de stukjes volledig vrij waren van mesofylcellen of nerfweefsel, dan vond daarin geen virusvermeerdering plaats tijdens een incubatie van 2 of 4 dagen op agar. Als na het strippen nog enkele mesofylcellen of nerfstukjes aanwezig waren, kon wel enige virusactiviteit in de homogenaten worden aangetoond.In cowpeabladeren die geïnoculeerd werden met de cowpea-stam van TMV of de normale stam van TMV had infectieus virusmateriaal al binnen 10 min na inoculatie het mesofyl bereikt. Blijkbaar is in cowpeabladeren de epidermis niet noodzakelijk voor de binnenkomst van virus of voor de necroseproduktie na virusinoculatie.  相似文献   

3.
Zoospores of 12 isolatesO. bornovanus from geographically diverse sites and representing the three host specific cucurbit strains were tested as vectors for seven viruses using watermelon bait plants and the in vitro acquisition method. All isolates of the cucumber, melon, and squash strains transmitted melon necrotic spot carmovirus (MNSV) and cucumber necrosis tombusvirus (CNV) but none transmitted petunia asteroid mosaic tombusvirus (PAMV) or tobacco necrosis necrovirus (TNV). The isolates varied as vectors of three other carmoviruses: cucumber leaf spot virus (CLSV); cucumber soil borne virus (CSBV); and squash necrosis virus (SqNV). All cucumber isolates transmitted CLSV and SqNV but not CSBV. Some of the melon isolates transmitted CLSV and SqNV but none transmitted CSBV. Two squash isolates transmitted CSBV and SqNV but not CLSV. Two isolates ofO. brassicae transmitted only TNV and a third did not transmit any of the viruses. The species of bait plant sometimes affected transmission. The most efficient vector strains ofO. bornovanus, as determined by reducing zoospores and virus in the inoculum, were the cucumber strain for CLSV; the cucumber strain for CNV if cucumber was the bait plant or melon strain if watermelon was the bait plant; and the squash strain for SqNV. The plurivorous strain ofO. brassicae was the most efficient vector of TNV.Olpidium bornovanus is the first vector reported for CSBV and is confirmed as a vector of SqNV. It is proposed that all carmoviruses may have fungal vectors.Ligniera sp. did not transmit any of the viruses in one attempt.Abbreviations CLSV cucumber leaf spot virus - CNV cucumber necrosis virus - CSBV cucumber soil borne virus - MNSV melon necrotic spot virus - PAMV petunia asteroid mosaic virus - SqNV squash necrosis virus - TNV tobacco necrosis virus - TBSV tomato bushy stunt virus  相似文献   

4.
Systemic acquired resistance induced in intact ‘Samsun NN’ tobacco plants by either tobacco mosaic virus (TMV) or tobacco necrosis virus (TNV) was more effective against challenge inoculation with the same than with the other of the two viruses. However, in trimmed ‘Samsun NN’ plants resistance induced by either of these viruses was stronger against TMV than against TNV. In intact ‘Samsun’ tobacco plants TNV induced a systemic resistance against itself identical to the one expressed in ‘Samsun NN’. Moreover, it induced systemic resistance against TMV as based on a decrease in TMV content in challeng-inoculated leaves. These observations indicate that systemic acquired resistance is not limited to combinations in which both inducing and challenging virus give rise to a hypersensitive reaction, and further point to virus-specific factors regulating the extent of resistance expressed.  相似文献   

5.
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6.
Bacillus cereus C1L has been demonstrated to induce systemic disease resistance against Botrytis elliptica in lily. The objective of this study was to investigate physiological responses of B. cereus C1L-triggered systemic resistance in lily cv. Star Gazer against B. elliptica. By histological and biochemical analyses, leaves inoculated with B. elliptica displayed cell death, H2O2 accumulation and lignin deposition. As plants were elicited with B. cereus C1L, cell death, H2O2 accumulation and lignin deposition in leaves caused by B. elliptica infection were suppressed, revealing that suppression of oxidative burst might be associated with B. cereus C1L-induced systemic resistance. In reactive oxygen species inhibitors assays, B. elliptica-caused lesion numbers and H2O2 accumulation in lily leaves were significantly reduced as leaves were pretreated with catalase or diphenylene iodonium. Furthermore, the expression of LsGRP1 and LsPsbR in leaves elicited with B. cereus C1L and inoculated with B. elliptica was decreased. The same expression pattern was also observed in leaves pretreated with catalase or diphenylene iodonium and inoculated with B. elliptica. These results suggest that B. cereus C1L-induced systemic resistance may be related to suppression or alleviation of oxidative stress and cell death of lily caused by B. elliptica.  相似文献   

7.
Local lesion formation on cowpea leaves was more than 50% inhibited by treatment with a 23 kDa RNase-like glycoprotein from Cucumis figarei, figaren, from 24 hr before to 1 hr after inoculation with Cucumber mosaic virus (CMV). CMV accumulation detected by ELISA in tobacco leaves treated with figaren 6 or 0 hr before inoculation with CMV was suppressed. When upper leaves of tobacco plants were treated with figaren and inoculated 10 min later with CMV, mosaic symptoms were delayed for 5–7 days on most of the tobacco plants, and some plants remained asymptomatic. From fluorescence in situ hybridization, infection sites were present in figaren-treated cowpea or melon leaves after inoculation with CMV, though the sites were reduced in number and size compared with those in water-treated control leaves. The amount of CMV RNAs and CMV antigen in melon protoplasts inoculated with CMV and subsequently incubated with figaren similarly increased with time as did that in the control. ELISA and local lesion assays indicated that CMV infection on the upper surfaces of the leaves of tobacco, melon, cowpea and C. amaranticolor whose lower surfaces had been treated with figaren 5–10 min before CMV inoculation was almost completely inhibited. Figaren did not inhibit CMV infection on the opposite untreated leaf halves of melon, cowpea and C. amaranticolor, whereas it almost completely inhibited CMV infection on the untreated halves of leaves of tobacco. CMV infection was not inhibited in the untreated upper or lower leaves of the four plants. These data suggest that figaren does not completely prevent CMV invasion but does inhibit the initial infection processes. It may also induce localized acquired resistance in host plants. Received 10 October 2000/ Accepted in revised form 6 February 2001  相似文献   

8.
The effects of zucchini yellow mosaic virus (ZYMV) infection and pretreatments with salicylic acid (SA) on biomass accumulation of pumpkin (Cucurbita pepo cv. Eskandarani) were investigated. The response of photosynthesis, transpiration and the activities of antioxidant enzymes in leaves was also considered. Significant reductions in growth parameters (i.e. leaf area, biomass and shoot height), photosynthesis and chlorophyll a and b content were detected in ZYMV-infected leaves in comparison to healthy controls. Antioxidant enzyme activities were increased up to 3-fold for peroxidase (POD), 2-fold for ascorbate peroxidase (APX) and catalase (CAT) activities and 1.3-fold for SOD activity by virus infection. ZYMV infection also caused increases in H2O2 and malondialdehyde (MDA) contents. These results suggest that ZYMV infection causes oxidative stress in pumpkin leaves leading to the development of epidemiological symptoms. Interestingly, spraying pumpkin leaves with SA led to recovery from the undesirable effects of ZYMV infection. Leaves treated with 100 μM SA three days before inoculation had the appearance of healthy leaves. No distinct disease symptoms were observed on the leaves treated with 100 μM SA followed by inoculation with ZYMV. In non-infected plants, SA application increased activities of POD and superoxide dismutase (SOD) and inhibited APX and CAT activities.In contrast, SA treatment followed by ZYMV inoculation stimulated SOD activity and inhibited activities of POD, APX and CAT. In addition, MDA displayed an inverse relation, indicating inhibition of lipid peroxidation in cells under SA treatment. It is suggested that the role of SA in inducing plant defense mechanisms against ZYMV infection might have occurred through the SA-antioxidant system. Such interference might occur through inhibition or activation of some antioxidant enzymes, reduction of lipid peroxidation and induction of H2O2 accumulation following SA application.  相似文献   

9.
The effects of zucchini yellow mosaic virus (ZYMV) infection and pretreatments with salicylic acid (SA) on biomass accumulation of pumpkin (Cucurbita pepo cv. Eskandarani) were investigated. The response of photosynthesis, transpiration and the activities of antioxidant enzymes in leaves was also considered. Significant reductions in growth parameters (i.e. leaf area, biomass and shoot height), photosynthesis and chlorophyll a and b content were detected in ZYMV-infected leaves in comparison to healthy controls. Antioxidant enzyme activities were increased up to 3-fold for peroxidase (POD), 2-fold for ascorbate peroxidase (APX) and catalase (CAT) activities and 1.3-fold for SOD activity by virus infection. ZYMV infection also caused increases in H2O2 and malondialdehyde (MDA) contents. These results suggest that ZYMV infection causes oxidative stress in pumpkin leaves leading to the development of epidemiological symptoms. Interestingly, spraying pumpkin leaves with SA led to recovery from the undesirable effects of ZYMV infection. Leaves treated with 100 μM SA three days before inoculation had the appearance of healthy leaves. No distinct disease symptoms were observed on the leaves treated with 100 μM SA followed by inoculation with ZYMV. In non-infected plants, SA application increased activities of POD and superoxide dismutase (SOD) and inhibited APX and CAT activities.In contrast, SA treatment followed by ZYMV inoculation stimulated SOD activity and inhibited activities of POD, APX and CAT. In addition, MDA displayed an inverse relation, indicating inhibition of lipid peroxidation in cells under SA treatment. It is suggested that the role of SA in inducing plant defense mechanisms against ZYMV infection might have occurred through the SA-antioxidant system. Such interference might occur through inhibition or activation of some antioxidant enzymes, reduction of lipid peroxidation and induction of H2O2 accumulation following SA application.  相似文献   

10.
Analysis on polyacrylamide gels of the soluble protein fraction of cucumber cotyledons infected with tomato spotted wilt virus (TSWV) revealed a stimulated protein component, designated as protein E1. The amount of protein E1 was related to the size and number of local lesions produced on the inoculated cotyledons. Protein E1 stained positive for carbohydrate and could be partly purified by gel filtration on Sephadex G 100. The molecular weight was estimated to be approximately 22000 d. Protein E1 seems to be serologically unrelated to any of the structural proteins of TSWV. Following inoculation of cucumber cotyledons with the yellow strain of cucumber mosaic virus (CMV), a protein with identical mobility on 7.5 and 10% polycrylamide gels to protein E1 was detected. These proteins are probably identical and their accumulation is a result of the infection process. There was a close correspondence between the amount of protein E1 and the severity of symptom expression. A protein with a mobility differing slightly from protein E1 occurred in the soluble protein fraction ofNicotiana rustica after infection with either TSWV or tobacco mosaic virus.  相似文献   

11.
In this study, we examined the necrosis phenotype on leaves of two cultivars of soybean (ZheA8901 and Nannong1138-2) that show varying level of resistance to soybean mosaic virus (SMV). The necrotic symptoms seen on inoculated and systemic leaves of soybean cultivar ZheA8901 were reminiscent of programmed cell death (PCD). The cell death phenotypes were evaluated using the TUNEL method, quantification of hydrogen peroxide (H2O2) and salicylic acid, callose production, as well as by monitoring expression of defence genes GmPR-1 and GmNPR1. Our results show that SMV inoculation induced PCD on ZheA8901 is associated with rapid increase in H2O2, increased SA and callose accumulation and higher defence gene expression.  相似文献   

12.
The time required for infectious tobacco necrosis virus (TNV) to pass through the epidermis of cowpea leaves after mechanical inoculation, depended on plant age and environmental temperature. At 22°C the passage time was about 2 h but at 32°C it was only 10 min. Water stress seemed to play a role in the transport of infectious virus into the mesophyll. It was possible to infect cowpea mesophyll cells with TNV directly by using a fine brush without carborundum. Differences between tobacco and cowpea in the establishment of virus infection are discussed.Samenvatting De mogelijkheden om cowpea-mesofylcellen met TNV te infecteren, hetzij via de epidermis, hetzij rechtstreeks, werden onderzocht. De minimum tijd die infectieus virusmateriaal nodig heeft om de epidermis te passeren werd bepaald. De ouderdom van de zaailingen speelde daarbij een rol. Bij 20 dagen oude planten bedroeg de passagetijd meer dan 4 uur, in 10 dagen oude planten was meer dan 2 uur nodig voor passage. De temperatuur van de omgeving was een belangrijke factor. In cowpeabladeren, direct na inoculatie met TNV bij 32°C gezet, bleek de passgetijd slechts 10 minuten te zijn. Verduistering van de planten 24 uur voor inoculatie bekortte de passagetijd aanzienlijk. Ook speelde water-stress in het blad door hoge temperatuur na inoculatie een rol in de vroege infectiestadia. Het was mogelijk, cowpea-mesofyl direct te infecteren, indien cowpea-bladeren gebruikt werden van 9–12 dagen oude zaailingen die opgekweekt waren bij 22±3°C. De bladeren werden gedurende ±1 uur na afplukken op droog filtreerpapier gelegd, daarna werd de onderepidermis met een fijn pincet verwijderd. Inoculatie van het naakte mesofyl met TNV onmiddelljk na het strippen met een fijne penseel zonder carborundum resulteerde in eenzelfde aantal lesies als in de niet-gestripte helft, die geïnoculeerd was door wrijven met hetzelfde TNV-inoculum in aanwezzigheid van carborundum.Het schijnt dat de processen, die betrokken zijn bij het tot stand komen van een TNV-infectie in cowpea en tabak, van elkaar verschillen.  相似文献   

13.
施用纳米氧化锌对小麦籽粒锌含量和锌利用率的影响   总被引：1，自引：0，他引：1  
采用田间小区试验,设置不施锌、土施硫酸锌、喷施硫酸锌、土喷结合硫酸锌以及土施纳米氧化锌、喷施纳米氧化锌和土喷结合纳米氧化锌7个处理,研究了不同锌肥施用方式对小麦产量、锌等微量元素含量和累积量以及锌利用率的影响。结果表明,各施锌处理对小麦籽粒产量均没有显著影响,而施用纳米氧化锌则显著增加籽粒锌含量,单独土施使锌含量从对照的18.9 mg·kg~(-1)增加至24.6 mg·kg~(-1),增幅达30%;单独喷施籽粒锌含量增加至28.4 mg·kg~(-1),增幅达50%;土喷结合处理籽粒锌含量增加至30.2 mg·kg~(-1),增幅达60%。单独喷施纳米氧化锌处理较硫酸锌处理提高籽粒锌强化指数近3倍,达到9.7 mg·kg~(-1);籽粒铁含量较喷施硫酸锌提高近2.5倍,达到58.9mg·kg~(-1)。同时,单独喷施纳米氧化锌显著增加了叶片锌累积量,使得地上部锌利用率达到35%,较硫酸锌处理增加近4倍,差异达到显著水平。由此可见,喷施纳米氧化锌较硫酸锌对提高小麦籽粒锌铁含量有更好的效果,可能由于纳米颗粒的小尺寸效应降低了叶片上锌的脱落。  相似文献   

14.
When exposed to light, the Sekiguchi lesion (sl) rice mutant has an enhanced resistance to Magnaporthe grisea infection responsible for Sekiguchi lesion formation and tryptamine accumulation. Glyphosate [N-(phosphonomethyl) glycine] pretreatment suppressed Sekiguchi lesion formation and tryptamine accumulation in the sl mutant after M. grisea infection even under light. This inhibition by glyphosate was blocked by the supply of exogenous tryptophan, but not by exogenous phenylalanine. In glyphosate-pretreated leaves, 5-enol-pyruvyl-shikimate-3-phosphate synthase gene expression and tryptophan biosynthesis were significantly suppressed. During tryptophan starvation, catalase activity was maintained at a high level even under light, leading to the suppression of H2O2 generation and DNA fragmentation. These results show a strong relationship between the tryptophan and tryptamine pathways in the induction of light-enhanced resistance to M. grisea infection in the sl mutant.  相似文献   

15.
Rapidly spreading lesions and lesions restricted in size developed in primary leaves of French bean (Phaseolus vulgaris) in response to infection byBotrytis cinera isolates BC-1 and BC-5, respectively. These isolates caused similar differential lesions in leaves of cucumber, flax, lettuce and tomato. To determine whether phytoalexin accumulation was correlated with the resistant reaction in bean leaves, accumulation of phytoalexins was examined in necrotic areas of both types of lesions and in their surrounding green tissues. Phaseollin was the predominant phytoalexin, both inside and outside lesions, whereas phaseollidin and sometimes also phaseollinisoflavan were always present in lower concentrations. Phaseollin accumulated earlier and to higher levels within and around lesions of isolate BC-5 than of isolate BC-1. Relatively low concentrations of phaseollin were detected in the more remote green areas, including the petiole, of leaves bearing a spreading lesion. The phaseollin metabolite, 6a-hydroxyphaseollin, was found only inside lesions and in a narrow zone around lesions of both types. The authors consider the possibility that the differing concentrations of phytoalexins in the infected tissues are not a determining factor for the differential interactions betweenB. cinerea and bean leaves, but are rather the result of it.  相似文献   

16.
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17.
This paper questions whether pathogenesis-related proteins (PRs) have any role in acquired systemic resistance, and whether there may be alternative explanations for the reduced number and size of lesions formed when leaves containing PRs are inoculated with virus. It is concluded that PRs may not play a direct role in acquired resistance; that altered lesion number may result from altered susceptibility of the leaf to mechanical inoculation, and that reduced lesion size could reflect a non-specific modulation of the basic localization mechanism. Preliminary experiments showing changes in ultrastructure of leaves associated with the development of acquired systemic resistance are discussed. The most striking change was development of myelinic bodies, generally between the cell wall and plasmalemma in uninoculated areas of leaf opposite halves bearing lesions.  相似文献   

18.
A carlavirus was isolated from leaves of a dandelion plant raised in the experimental garden of the Hugo de Vries Laboratory in Amsterdam. The virus was readily sap-transmissible and infected 24 out of the 52 plant species and cultivars tested, with visible symptoms in 18 of them.Myzus persicae andCuscuta subinclusa (dodder) did not transmit the virus. In addition the virus was not seed-transmitted in dandelion. Dilution end-point was 10–5, thermal inactivation occurred at between 80–85°C and longevity in vitro was approximately 24h. The virus had a sedimentation coefficient of 136 S. Polyacrylamide gel electrophoresis of the coat protein gave two bands, consisting of proteins with molecular masses ranging from 37 000 to 34 300 Da (band I) and from 34 000 to 32 800 Da (band II). The molecular mass of the RNA was 2.84 x 106 Da. The average buoyant density of the virus was 1.306 gcm–3 and the average A260/A280 ratio 1.16. The virus particles had a normal length of 668 nm. with the light microscope, large mainly vacuolate inclusions were observed in the epidermal cells of infectedNicotiana cleavelandii leaves. In ultra-thin sections of systemically infected leaves ofN. clevelandii, bundles of aggregated virus particles were detected, whereas in infected dandelion leaves there were fewer aggregates and more scattered virus particles. There was a close serological relationship to dandelion latent virus, chrysanthemum virus B and potato virus S and a more distant one to carnation latent virus, elderberry carlavirus,Helenium virus S and potato virus M. The occurrence of the virus was found to be restricted to dandelion plants in the experimental garden in Amsterdam. On the basis of large differences in host range, symptomatology and lack of transmission byM. persicae it was decided that the virus could not be considered a strain of either dandelion latent virus, chrysanthemum virus B or potato virus S. We therefore propose that it be called dandelion carlavirus.Samenvatting Een carlavirus werd geïsoleerd uit een paardebloemplant, die opgekweekt was in de proeftuin van het Hugo de Vries-Laboratorium in Amsterdam. Het virus kon gemakkelijk met sap worden overgebracht en was in staat 24 van de 52 getoetste plantesoorten en-cultivars te infecteren, waarbij op 18 van deze symptomen zichtbaar werden.Myzus persicae en warkruid (Cuscuta subinclusa) konden het virus niet overbrengen. Evenmin kon het virus met zaad van geïnfecteerde planten van paardebloem overgaan. De verdunningsgrens was 10–5, de inactiveringstemperatuur 80–80°C en de houdbaarheid in vitro ongeveer 24 uur. Het virus had een sedimentatiecoëfficiënt van 136 S. Polyacrylamide-gelelektroforese van het manteleiwit resulteerde in twee banden, bestaande uit eiwitten met molecuulmassa's die varieerden van 37000 tot 34 3000 Da (band I) en van 34 000 tot 32 800 Da (band II). De molecuulmassa van het RNA was 2,84×106Da. De gemiddelde zweefdichtheid van het virus bedroeg 1,306g cm–3 en de gemiddelde A260/A280 verhouding was 1,16. Het virus had een normale lengte van 668 nm. In de epidermiscellen van geïnfecteerde bladeren vanNicotiana clevelandii werden met de lichtmicroscoop insluitsels met draderige en vacuoleachtige structuren waargenomen. In ultradunne coupes van systemisch geïnfecteerde bladeren vanN. clevelandii waren bundels geaggregeerde virusdeeltjes zichtbaar. In geïnfecteerde bladeren van paardebloem werden daarentegen meer verspreid voorkomende virusdeeltjes gevonden en minder aggregaten. Het virus vertoonde een sterke serologische verwantschap met het dandelion latent virus, chrysantevirus B en aardappelvirus S; er was een geringe verwantschap met het latente anjervirus, het carlavirus van vlier, Helenium virus S en het aardappelvirus M. Het vóórkomen van het virus bleek beperkt te zijn tot paardebloemen in de proeftuin in Amsterdam. Gezien de grote verschillen in waardplantenreeks, symptomatologie en overdracht metM. persicae hebben we gemeend, dat het virus niet slechts als een stam kon worden beschouwd van hetzij het dandelion latent virus, hetzij het chrysantevirus B en het aardappelvirus S. We stellen voor de naam carlavirus van paardebloem aan dit virus te geven.  相似文献   

19.
An antiviral protein, designated figaren, was purified from leaves of Cucumis figarei and partially characterized. Column chromatography, SDS-polyacrylamide gel electrophoresis and periodic acid-Schiff staining revealed that figaren is a glycoprotein with a molecular weight of 23 kDa. Figaren was stable at pH 2 to 12 and below 90°C. N-terminal amino acid sequencing indicated that figaren contained the conserved region for the S-allele-associated ribonucleases (RNases). In-gel RNase assay showed that figaren digested yeast RNAs. Figaren also digested double-stranded RNAs extracted from Cucumber mosaic virus (CMV)-infected tobacco tissues. Fluorescence in situ hybridization revealed that figaren and RNases (beef pancrease and RNase T1 at 1 μg/ml similarly inhibited CMV infection in cowpea leaves. Figaren and the RNases at 5-500 ng/ml had similar inhibitory effect on local lesion formation by CMV. These data suggest that figaren is a novel RNase-like antiviral protein. Received 10 October 2000/ Accepted in revised form 6 February 2001  相似文献   

20.
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.  相似文献   

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