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1.
The effects of tobacco mosaic virus synthesis on the free amino acid and amide composition of the host
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1. Changes in concentrations of free amino acids and amides have been determined in TMV-infected tobacco leaf discs and in comparable uninfected discs during the time of virus formation. 2. During the period of rapid virus formation the infected discs show a transitory deficiency (as compared to uninfected discs) in glutamine, asparagine, aspartic acid, glutamic acid, serine, and to a lesser extent in valine, threonine, and proline. About 100 hours before this time smaller deficiencies in the concentrations of these components also occur. The latter effect is probably associated with the early synthesis of a non-virus protein in infected tissue. 3. Comparison of the above effects with the known amino acid composition of TMV indicates that it is unlikely that the virus protein is synthesized by condensation of appropriate free amino acids. Rather, the deficiencies observed appear to result from removal of ammonia from the nitrogen pool during synthesis of new proteins in infected tissue. Equilibrium shifts resulting from ammonia withdrawal probably account for the observed deficiencies in amides and free amino acids. TMV protein, therefore, appears to be synthesized de novo, from non-protein nitrogen, probably ammonia. 4. It is suggested that the changes in free amino acid concentrations induced by virus formation may account for some of the symptoms observed in infected plants. 相似文献
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3.
Summary Conditions optimal for the infection of Brassica leaf protoplasts by turnip yellow mosaic virus (TYMV) were found to be: pH 5.4–5.8 with citrate buffer; concentration of poly-L-ornithine, 0.8–1.0 g/ml; concentration of TYMV, 0.2–1.0 g/ml. More than 90% of Brassica rapa and B. sinensis protoplasts were infected under these conditions. TYMV replication in Brassica protoplasts was followed by quantitating the virus extracted from protoplasts and separated by sucrose density gradient centrifugation. Brassica protoplasts produced 1 to 2x106 TYMV particles per cell within 48 hrs. Infection by TYMV induced the formation of polyplasts (aggregates of chloroplasts) in Brassica protoplasts. Polyplast formation paralleled the appearance of TYMV-specific immunofluorescence and could thus be used conveniently to determine the number of infected protoplasts. TYMV replication in Brassica protoplasts was resistant to actinomycin D and chloramphenicol, but was completely inhibited by cycloheximide. 相似文献
4.
1. Discs cut from tobacco leaf tissue infected with tobacco mosaic virus and cultured in water contain less non-protein nitrogen than comparable uninfected discs during the time at which TMV is formed. This deficiency disappears when virus formation ceases. Discs cultured in nutrient solution form about twice as much TMV as discs cultured in water. The maximum non-protein nitrogen deficiency is comparable in magnitude to the amount of virus synthesized. 2. The largest difference between injected and uninfected tissue occurs in the ammonia content. Smaller, but significant differences in amide content are found. Infected discs cultured in water show no significant differences from control discs in free amino acid content; infected discs cultured in nutrient solution develop a small deficiency in amino acid nitrogen. 3. The general patterns of change in composition of the pool of soluble nitrogen are similar in both infected and uninfected discs. 4. The data indicate that the bulk of the nitrogen incorporated into virus protein is withdrawn from the leaf's pool of soluble nitrogen; virus is formed de novo from ammonia nitrogen and non-nitrogenous carbon sources. The effect of virus infection on host nitrogen metabolism appears to be due to the formation of virus rather than to its presence. 相似文献
5.
The synthesis of polyamines from methionine in intact and disrupted leaf protoplasts of virus-infected chinese cabbage 总被引:3,自引:2,他引:1
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In exploring the role of the chloroplast in the multiplication of turnip yellow mosaic virus, the biosyntheses of the major viral polyamine, spermidine, as well as that of the tetramine, spermine were studied. The synthesis of these polyamines from [2-14C]methionine in protoplasts of Chinese cabbage leaf cells derived from healthy plants or those infected by turnip yellow mosaic virus were examined. Populations of protoplasts of infected leaves are homogeneous with respect to containing chloroplast aggregates in contrast to those of healthy leaves. Protoplast preparations have been shown to incorporate methionine into protein, spermidine, and spermine more rapidly than do fresh leaf discs, which also show a very slow utilization of labeled arginine and ornithine into polyamine. 相似文献
6.
Effects of turnip mosaic virus and turnip yellow mosaic virus on the survival, growth and reproduction of wild cabbage (Brassica oleracea) 总被引:1,自引:0,他引:1
L. C. MASKELL A. F. RAYBOULD J. I. COOPER M-L EDWARDS A. J. GRAY 《The Annals of applied biology》1999,135(1):401-407
Wild plants of Brassica oleracea (wild cabbage) are commonly infected with turnip mosaic poty virus (TuMV), turnip yellow mosaic tymovirus (TYMV) and several other viruses. A field experiment in which plants were inoculated either with TuMV or TYMV showed that virus infection significantly reduced survival, growth and reproduction. Relative to water inoculated-controls, plants infected with TYMV had greater mortality, were shorter, had a smaller leaf area and number, showed a greater amount of damage from herbivory and chlorosis, were less likely to flower and produced fewer pods and lower total seed output. Plants infected with TuMV did not appear to be adversely affected at first; however, mortality after 18 months was higher than control plants. Although TuMV infection had no effect on the number of plants flowering, the infected plants did produce fewer pods and a lower total seed output. We conclude that both viruses can significantly affect vegetative and reproductive performance of wild cabbage and hence that introgression of virus resistance (particularly when conferred by a major gene or a transgene) from a crop might increase plant fitness in natural populations of this species. Ecological risk assessments of virus resistance transgenes must do more than survey adult plants in natural populations for the presence of the target virus. Failure to detect the virus could be due to high mortality on infection with the virus. 相似文献
7.
Tobacco (Nicotiana tabacum L., cv. Samsun) leaf discs inoculated with tobacco mosaic virus (TMV) were treated with auxin-like herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 3-amino-1,2,4-triazol (Amitrol) and 6-chloro-2-ethylamino-4-isopropylamino-1,3,5-triazine (Atrazin). All herbicides in the concentration of 10–7 M enhanced the virus content (MCPA to 227.4 %, Amitrol to 218.1 % and Atrazin to 257.3 % of values found in TMV-infected, herbicide untreated discs). The 2,4-D alone did not affect the activity of the glucose-6-phosphate dehydrogenase and ribonucleases, but the 2,4-D treatment together with TMV infection raised their activities twice as high as in the untreated control discs. Polyacrylamide gel electrophoresis of acidic extracellular proteins washed from leaf discs treated with 2,4-D did not prove the induction of PR-proteins. 相似文献
8.
The prevalence and spatial distribution of viruses in natural populations of Brassica oleracea 总被引:1,自引:0,他引:1
A. F. RAYBOULD L. C. MASKELL M-L. EDWARDS J. I. COOPER & A. J. GRAY 《The New phytologist》1999,141(2):265-275
We report a survey of four viruses (beet western yellows luteovirus (BWYV), cauliflower mosaic caulimovirus (CaMV), turnip mosaic potyvirus (TuMV), turnip yellow mosaic tymovirus (TYMV)) in five natural populations of Brassica oleracea in Dorset (UK). All four viruses were common; 43% of plants were infected with BWYV, 60% with CaMV, 43% with TuMV and 18% with TYMV. For each virus there were significant differences in the proportion of infected plants among populations, which were not completely explained by differences in the age of plants. Multiple virus infections were prevalent, with 54% of plants having two or more virus types. There were statistically significant associations between pairs of viruses. The CaMV was positively associated with the other three viruses, and BWYV was also positively associated with TuMV. There was no detectable association between BWYV and TYMV, whereas TuMV and TYMV were negatively associated. We suggest these associations result from BWYV, CaMV and TuMV having aphid vectors in common, as aphids are attracted to plants that already have a virus infection. Infected plants were distributed randomly or were very weakly aggregated within populations. The implications of widespread multiple virus infections in natural plant populations are discussed with respect to the release of transgenic plants expressing virus-derived genes. 相似文献
9.
应用基因突变技术,在烟草黄矮双生病毒(Tobacoyelowdwarfgeminivirus,简称TobYDV)基因组的正义和反义链引入或缺失碱基,从而构建成一系列移码突变体。这些突变体在个别感染的情况下,全部丧失了系统侵染三生烟植株的能力,但是,成对地进行接种,能发生持久的互补作用,重新获得系统侵染的能力。突变体的互补作用发生在重组之前。在个别感染的叶块组织中,各种反义链突变体丧失了复制能力,然而,突变体V1-、V2-和V1-V2-能高度复制,表明反义链读码框编码产物为复制所必需,V1和V2读码框编码产物与复制无关,而为病毒的转移所必需。从V1-和V2-转化叶块中再生转基因植株,发现V1-和V2-都能在植株中维持复制,但是,只有V1-引起典型的病症,表明V1编码产物与病症出现无关。这些结果将为发展TobYDV为载体,在寄主植物中高度复制和表达外源基因提供依据。 相似文献
10.
The effect of inhibitors of glutathione (GSH) synthesis, namely gamma-methyl glutamic acid, d-glutamic acid, cystamine, methionine-S-sulfoximine (MSX), buthionine-S-sulfoximine, and GSH itself, on the emission of H(2)S was investigated. All these compounds stimulated H(2)S emission from pumpkin (Cucurbita pepo L. cv Small Sugar Pumpkin) leaf discs in response to sulfate. MSX and GSH were the most effective compounds, stimulating H(2)S emission from leaf discs of mature pumpkin leaves by about 80% in response to sulfate. Both inhibitors did not appreciably enhance H(2)S emission in response to l-cysteine and inhibited H(2)S emission in response to sulfite.Treatment with MSX or GSH enhanced the uptake of sulfate by pumpkin leaf discs, but did not affect the incorporation of sulfate into reduced sulfur compounds. Inhibition of GSH synthesis by MSX or GSH caused an increase in the pool size of cysteine, and, simultaneously, reduced the incorporation of labeled sulfate into cysteine. The incorporation of labeled sulfate into the sulfite and sulfide pools of the cells are stimulated under these conditions.These observations are consistent with the idea that inhibition of GSH synthesis leads to an elevated cysteine pool that inhibits further cysteine synthesis. The H(2)S emitted under these conditions appears to arise from diversion of a precursor of the sulfur moiety of l-cysteine. Therefore, stimulation of H(2)S emission in response to sulfate upon inhibition of GSH synthesis may reflect a role of H(2)S emission in keeping the cysteine concentration below a critical level. 相似文献
11.
The ability to detect Odontoglossum ringspot virus (ORSV) released from the cut surfaces of leaf discs by ELISA was examined. Results indicate that ORSV from leaf discs can be detected but that multiple discs are necessary to obtain reliable detection of low virus concentrations, ELISA of Cymbidium protocorms, known from immunosorbent electron microscopy to be infected with ORSV, frequently produced A435 values which would be considered either negative or marginally positive on the basis of commonly accepted statistical limits (i, e. 2 x mean, or mean + 3 x standard deviation). The comparison of paired samples, one of which had been pretteated with ORSV antiserum, improved the sensitivity of the test from 10 ng ml ‘’ of virus to 2 ng ml’. 相似文献
12.
Metabolic regulation of glycolate synthesis, photorespiration, and net photosynthesis in tobacco by L-glutamate 总被引:11,自引:10,他引:1
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Experiments were undertaken to identify and characterize control mechanisms in tobacco leaf tissue which decrease the relative contribution of photorespiratory CO2 release and thereby increase net photosynthetic CO2 fixation. A number of metabolites were supplied to illuminated leaf discs and their effect on the inhibition of glycolate synthesis was measured. Glycolate accumulation, in the presence of α-hydroxy-2-pyridinemethanesulfonic acid, was inhibited in leaf discs previously floated on 30 mM solutions of either L-glutamate, L-aspartate, phospho-enolpyruvate, or glyoxylate. The effect of glutamate on glycolate synthesis, which was investigated in detail, was concentration- and time-dependent. Glycolate synthesis was inhibited about 40% by treating leaf discs with 30 mM glutamate, and the inhibition continued for more than 4 hours after the glutamate solution was removed. 相似文献
13.
Turnip yellow mosaic virus (TYMV) is a spherical plant virus that has a single 6.3 kb positive strand RNA as a genome. In this study, RNA1 sequence of Flock house virus (FHV) was inserted into the TYMV genome to test whether TYMV can accommodate and express another viral entity. In the resulting construct, designated TY-FHV, the FHV RNA1 sequence was expressed as a TYMV subgenomic RNA. Northern analysis of the Nicotiana benthamiana leaves agroinfiltrated with the TY-FHV showed that both genomic and subgenomic FHV RNAs were abundantly produced. This indicates that the FHV RNA1 sequence was correctly expressed and translated to produce a functional FHV replicase. Although these FHV RNAs were not encapsidated, the FHV RNA having a TYMV CP sequence at the 3’-end was efficiently encapsidated. When an eGFP gene was inserted into the B2 ORF of the FHV sequence, a fusion protein of B2-eGFP was produced as expected. [BMB Reports 2014; 47(6): 330-335] 相似文献
14.
Comparison and functional implications of the 3D architectures of viral tRNA-like structures
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John A. Hammond Robert P. Rambo Megan E. Filbin Jeffrey S. Kieft 《RNA (New York, N.Y.)》2009,15(2):294-307
RNA viruses co-opt the host cell's biological machinery, and their infection strategies often depend on specific structures in the viral genomic RNA. Examples are tRNA-like structures (TLSs), found at the 3′ end of certain plant viral RNAs, which can use the cell's aminoacyl tRNA-synthetases (AARSs) to drive addition of an amino acid to the 3′ end of the viral RNA. TLSs are multifunctional RNAs involved in processes such as viral replication, translation, and viral RNA stability; these functions depend on their fold. Experimental result-based structural models of TLSs have been published. In this study, we further examine these structures using a combination of biophysical and biochemical approaches to explore the three-dimensional (3D) architectures of TLSs from the turnip yellow mosaic virus (TYMV), tobacco mosaic virus (TMV), and brome mosaic virus (BMV). We find that despite similar function, these RNAs are biophysically diverse: the TYMV TLS adopts a characteristic tRNA-like L shape, the BMV TLS has a large compact globular domain with several helical extensions, and the TMV TLS aggregates in solution. Both the TYMV and BMV TLS RNAs adopt structures with tight backbone packing and also with dynamic structural elements, suggesting complexities and subtleties that cannot be explained by simple tRNA mimicry. These results confirm some aspects of existing models and also indicate how these models can be improved. The biophysical characteristics of these TLSs show how these multifunctional RNAs might regulate various viral processes, including negative strand synthesis, and also allow comparison with other structured RNAs. 相似文献
15.
J. A. BAILEY 《The Annals of applied biology》1969,64(2):315-324
A sterile culture nitrate of Penicillium expansum was shown to induce pisatin synthesis in pea leaf discs. The amount of pisatin produced by pea leaves was shown to decrease as they underwent senescence. N6-benzyladenine delayed senescence, and at the same time maintained the production of pisatin at a high level. In darkness, leaf discs maintained on either benzyl-adenine solution or distilled water produced greater amounts of pisatin than leaf discs which were not treated in this way. Benzyladenine also increased pisatin production by leaf discs kept in the light. The relevance of these results to disease resistance and possible mechanisms involved are discussed. 相似文献
16.
RNA-coat protein interactions in turnip yellow mosaic virus (TYMV) have been shown to involve low pK proton-donating groups. Two different types of interaction have been proposed. In the so-called type I interaction, protonated C-residues interact with acidic amino acids at low pH, thereby providing a rationale for the high C-content (38%) of the genomic RNA. The type II interaction involves charged histidines interacting with phosphates of the RNA backbone. Site-directed mutagenesis of the TYMV coat protein and subsequent in vivo analysis were performed to distinguish between these two types of RNA-protein interaction. The results reveal a prominent role for the histidines H68 and H180, since mutation to an alanine residue inhibits symptom development on secondary leaves, indicating that spreading of the virus in the plant is blocked. Viral RNA and coat protein synthesis are not altered, showing that these two histidines may play a role in the process of RNA encapsidation. Overexpression of the TYMV coat protein in Escherichia coli leads to the formation of bona fide capsids, showing that the two histidines are not critical in capsid assembly. Mutagenesis of the acidic amino acids D11, E135, and D143 to alanine apparently did not interfere with virus viability. The functional role of the histidines during the infection cycle is discussed in terms of the structure of the coat protein, both at the level of amino acid sequence conservation among the members of the Tymoviridae family and as the three-dimensional structure of the coat protein. 相似文献
17.
The effect of different light qualities (blue, green, white, red and far-red) on ethylene production in leaf discs and flower petal discs of Begonia × hiemalis cv. Schwabenland Red was studied. All the light qualities, except far-red, reduced the ACC-conversion to ethylene in leaf discs by about 70% at a photosynthetic photon flux density (PPFD) of 20 mol m–2s–1.Blue and green light were less inhibitory than white and red light at lower PPFD. In all treatments far-red light at 0.5 mol m–2s–1 of photon flux density (PFD) stimulated the ACC-conversion to ethylene in leaf discs by about 60–90% compared to the dark-incubated control. White and red light strongly inhibited the -naphthalene-acetic acid (NAA) stimulated ethylene synthesis in leaf discs. The results may suggest that the ethylene production is controlled by phytochrome in the leaves but not in the petals. Lack of coaction of any light quality with silver ions on ethylene production in leaf and petal discs was also observed.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- EFE
ethylene forming enzyme
- NAA
-naphthalene-acetic acid
- PFD
photon flux density
- PPFD
photosynthetic photon flux density
- RH
relative air humidity
- SAM
S-adenosylmethionine
- STS
silver thiosulphate 相似文献
18.
Laser-Raman spectroscopy of the turnip yellow mosaic virus (TYMV) and its capsid indicate the following features of the structure and assembly of the virion. The secondary structure of coat-protein molecules in TYMV is comprised of 9 +/- 5% alpha-helix, 43 +/- 6% beta-sheet, and 48 +/- 6% irregular conformation and is not altered by the removal of the RNA from the capsid. Introduction of as many as 200 chain scissions per RNA molecule also does not affect the overall secondary structure of the encapsulated RNA, which is 77 +/- 5% in the A-helix form. Tryptophan and cysteine residues of the coat protein appear to be in contact with the solvent, while only one of three tyrosines per coat protein is available for hydrogen bonding of its p-hydroxyl group with H2O molecules. Both cytosine and adenine residues of TYMV RNA are protonated in substantial numbers near pH 4.5, suggesting elevation of their respective pKa values within the virion. The Raman data are consistent with chemical evidence favoring interaction between protonated bases of RNA and amino acid side chains of coat protein in TYMV. 相似文献
19.
Selection for wild type size derivatives of tomato golden mosaic virus during systemic infection. 总被引:3,自引:1,他引:3
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A chimeric tomato golden mosaic virus (TGMV) A component DNA, which results from replacement of the coding region of the viral coat protein gene (CP) with the larger bacterial beta-glucuronidase coding sequence (GUS), can replicate in agroinoculated leaf discs but is unstable in systemically infected plants (1). We have made similar replacements of the TGMV CP gene with the GUS coding sequence in both the sense and antisense orientations. Both derivatives replicated in leaf discs inoculated via Agrobacterium. However, systemic movement of the GUS substituted vectors was not detected in agroinoculated Nicotiana benthamiana plants. The only TGMV A derivatives detected in systemically infected leaves of inoculated plants were similar in size to the wild type viral component. Sequence analysis of derivatives from six independently inoculated plants revealed that they did not result from internal deletions of the larger replicons detected in leaf discs but, instead, were generated by fusion events occuring within the original T-DNA insert. These results indicate that systemic movement of TGMV in N. benthamiana plants provides a strong selective pressure favoring viral derivatives similar in size to the wild type virus components. 相似文献
20.
Turnip mosaic virus (TuMV) and cauliflower mosaic virus (CaMV) have been found infecting field crops of winter oilseed rape (Brassica napus ssp. oleifera) in South Warwickshire. Other viruses found include broccoli necrotic yellows virus (BNYV) and a member of the beet western yellows virus group. Systemic leaf symptoms caused by TuMV varied within and between cultivars; the three predominant reaction types were classified as necrotic, mosaic and immune. Some recently introduced cultivars of oilseed rape were more severely affected by TuMV infection than older cultivars. Reactions to CaMV were less varied and immunity was not found. The seed yield from TuMV and CaMV-infected plants was less than that of healthy control plants. This effect was due to infected plants producing either fewer seeds, smaller seeds or both. Germination of seeds from infected plants was unaffected if sown soon after harvest. After storage for one year the germination of seed from a virus infected plant was significantly less than that of seed from a virus-free plant. All commercial cultivars tested were experimentally susceptible to turnip yellow mosaic virus (TYMV) and some American strains of cucumber mosaic virus (CMV). 相似文献