On the specific difference in the local necrotic response to infection by tobacco mosaic and cabbage black ringspot viruses in tobaccos

Dědi?ně faktory podmiňující v rostlině schopnost reagovat na infekci virem mozaiky tabáku (Nicotiana virus 1) a virem ?erné krou?kovitosti zeli (Brassica virus 1) lokálními nekrotickými lézemi, resp. systémovoù infekcí, jsou u těchto dvou vir? Jen zdánlivě v inversní závislosti. Nicotiana tabacum var. Xanthi-nc, který získal nekrotický faktor z N. glutinosa, má je?tě nekrotický faktor pro infekci virem ?erné krou?kovitosti zelí.     

The relationship of potato black ringspot virus to tobacco ringspot and allied viruses

The relationship between potato black ringspot virus (PBRV), isolates of tobacco ringspot virus from blueberry (TRSV-B), cherry (TRSV-C) and calico-diseased potato (TRSV-P), and eucharis mottle virus (EuMV) was examined in tests of three types. In gel-diffusion precipitin tests, the reaction end-points of antisera, and spur formation, indicated that PBRV and TRSV-P are very closely related but not identical antigenically, as are TRSV-B and TRSV-C, and that these two pairs are more distantly related to each other and to EuMV. In plant-protection tests in Nicotiana angustifolia, PBRV, TRSV-B and EuMV conferred protection against the homologous virus but not against one another. PBRV, but not TRSV-B, conferred protection against TRSV-P. In tests with the two RNA species of PBRV, infectivity increased greatly when preparations of RNA-1 and RNA-2 were mixed, and both species are probably needed for infection. Infectivity did not increase when RNA-1 or RNA-2 of PBRV was mixed with RNA-2 or RNA-1, respectively, of TRSV-B; the two viruses seem too distantly related to form pseudo-recombinants. It is concluded that PBRV and tobacco ringspot virus should be considered separate viruses, and that TRSV-P should be considered a strain of PBRV. EuMV should perhaps be recognised as a virus distinct from, but related to, PBRV and tobacco ringspot virus.     

Identification of soybean mosaic, southern bean mosaic and tobacco ringspot viruses from soybean in the People's Republic of China

Samples of soybean plants with virus-like symptoms were collected from several locations in the People's Republic of China in 1981. These samples were used to prepare inocula for mechanical inoculation to soybean. Twenty-one virus cultures were obtained, the identities of which were determined by serology, symptomatology and host range. Sixteen cultures contained only soybean mosaic virus, four of which were more pathogenic than any previously studied; one culture contained only tobacco ringspot virus, another only southern bean mosaic virus, and three other cultures mixed infections of soybean mosaic and southern bean mosaic viruses. This is the first report of the occurrence of tobacco ringspot virus and southern bean mosaic virus in soybean in the People's Republic of China.     

Co-electroporation of rice protoplasts with RNAs of cucumber mosaic and tobacco mosaic viruses

Cucumber mosaic virus (CMV) RNA was used to study electroporation conditions suitable for protoplasts from rice suspension cultures. Rice protoplasts required a stronger and shorter electric pulse than tobacco protoplasts for introduction of viral RNA. Under optimized conditions, CMV infection was established in 65 % of electroporated protoplasts. In contrast, electroporation with tobacco mosaic virus (TMV) RNA did not result in infection of rice protoplasts. However, when TMV RNA was electroporated into rice protoplasts together with CMV RNA, TMV production was demonstrated in 15 % of protoplasts. Differential staining with fluorescent antibodies against the two viruses showed that the protoplasts producing TMV were without exception also infected by CMV. The results show that CMV replicates in rice protoplasts by itself, whereas TMV does so only with the aid of CMV.Abbreviations CMV cucumber mosaiv virus - PBS phosphate buffered saline - TMV tobacco mosaic virus.     

Effects of infection with the cabbage black ringspot strain of turnip mosaic virus on turnip as a host to Myzus persicae and Brevicoryne brassicae

When turnip plants with 3–7 leaves were inoculated with cabbage black ringspot virus (CBRSV) on the 3rd rough-leaf, symptoms only appeared on leaves that had been less than 15 mm long at the time of inoculation, although infection decreased the area and both fresh and dry weight of all leaves. Leaves were ‘aged’ by their appearance and placed in Leaf Age Categories (LACs). Leaves with symptoms senesced (‘aged’) prematurely. CBRSV-infection of cv. Green Top White did not change the distribution of populations of Myzus persicae between LACs, but increased the proportion of the plant suitable for colonisation. All suitable LACs were quickly colonised by adult apterae and nymphs. On CBRSV-infected plants the nymphal period was shorter, F₁ adults deposited larvae more frequently and the live body weight and tibial length of the F₂ generation was greater, than on healthy plants. The distribution of Brevicoryne brassicae populations on cv. Green Top White differed from that of M. persicae but was also unchanged by CBRSV-infection. On healthy plants the largest colonies were on mature leaves, so that on virus-infected plants premature senescence shortened the life of the colony. On CBRSV-infected plants the nymphal period was prolonged and the live weight of F₁ and F₂ adult apterae was less than on healthy plants. The differences between the biology of M. persicae and B. brassicae on CBRSV-infected cv. Green Top White were associated with the accelerated senescence of CBRSV-infected leaves. The possibility that CBRSV-infection might reduce the resistance of turnips to aphid infestation was tested. M. persicae and B. brassicae were cultured on two favourable and two less favourable cultivars. No improvement in population growth rate was found when the less favourable host cultivars were infected with CBRSV, but both aphid species weighed less and/or had smaller nymphal populations on cultivars showing the severest symptoms. These results are discussed in relation to the evolution of non-persistent virus transmission by aphids.     

Reproduction of sugar beet mosaic and tobacco mosaic viruses in anthocyanized beet plants

During our studies on the interaction of anthocyanins and plant virus diseases, reproduction of sugar beet mosaic (SBMV) and tobacco mosaic viruses (TMV) was investigated. Experiments were carried out in leaves of sugar beet,Beta vulgaris cv. Dobrovicka N and its spontaneous anthocyanized mutant. SBMV induces a systemic infection while TMV is responsible for primary local symptoms in sugar beet leaves only. Our quantitative analyses onAmaranthus caudatus L. andChenopodium quinoa Wilid. showed a significant decrease in concentration of SBMV in juice extracted from anthocyanized beet plants as compared with extracts from normal green infected plants. Significant differences were also obtained when SBMV — containing juice was tested in mixtures with healthy extracts from anthocyanized and normal green plants. Also the intensity of TMV symptoms in beet leaves was considerably decreased in leaves of antho-eyanized plants.     

Arabis mosaic and Prunus necrotic ringspot viruses in hop (Humulus lupulus L.)

Purified virus preparations made from nettlehead-diseased hop plants, or from Chenopodium quinoa, to which the virus was transmitted by inoculation of sap, contained polyhedral virus particles of 30 mμ diameter which were identified serologically as arabis mosaic virus (AMV). There were serological differences between AMV isolates from hop and from strawberry, and also differences in host range and in symptoms caused in C. quinoa and C. amaranticolor. AMV was always associated with nettlehead disease. The nematode Xiphinema diversicaudatum occurred in small numbers in most hop gardens, but was numerous where nettlehead disease was spreading rapidly. Preparations from nettlehead-affected hops also contained a second virus, serologically related to Prunus necrotic ringspot virus (NRSV), in mild and virulent forms which infected the same range of test plants but showed some serological differences. Mild isolates did not protect C. quinoa plants against infection by virulent isolates. Hop seedlings inoculated with virulent isolates of NRSV developed symptoms indistinguishable from those of split leaf blotch disease. Latent infection with NRSV was prevalent in symptomless hop plants. Nettlehead disease is apparently associated with dual infection of AMV and virulent isolates of NRSV. An unnamed virus with rod-shaped particles 650 mμ long was common in hop and was transmitted by inoculation of sap to herbaceous plants. Cucumber mosaic virus was obtained from a single plant of Humulus scandens Merr.     

Biological activities of hybrid RNAs generated by 3''-end exchanges between tobacco mosaic and brome mosaic viruses.

Sequences within the conserved, aminoacylatable 3' noncoding regions of brome mosaic virus (BMV) genomic RNAs 1, 2, and 3 direct initiation of negative-strand synthesis by BMV polymerase extracts and, like sequences at the structurally divergent but aminoacylatable 3' end of tobacco mosaic virus (TMV) RNA, are required in cis for RNA replication in vivo. A series of chimeric RNAs in which selected 3' segments were exchanged between the tyrosine-accepting BMV and histidine-accepting TMV RNAs were constructed and their amplification was examined in protoplasts inoculated with or without other BMV and TMV RNAs. TMV derivatives whose 3' noncoding region was replaced by sequences from BMV RNA3 were independently replication competent when the genes for the TMV 130,000-M(r) and 180,000-M(r) replication factors remained intact. TMV replicase can thus utilize the BMV-derived 3' end, though at lower efficiency than the wild-type (wt) TMV 3' end. Providing functional BMV RNA replicase by coinoculation with BMV genomic RNAs 1 and 2 did not improve the amplification of these hybrid genomic RNAs. By contrast, BMV RNA3 derivatives carrying the 3' noncoding region of TMV were not amplified when coinoculated with wt BMV RNA1 and RNA2, wt TMV RNA, or all three. Thus, BMV replicase appeared to be unable to utilize the TMV 3' end, and there was no evidence of intervirus complementation in the replication of any of the hybrid RNAs. In protoplasts coinoculated with BMV RNA1 and RNA2, the nonamplifiable RNA3 derivatives bearing TMV 3' sequences gave rise to diverse new rearranged or recombined RNA species that were amplifiable.     

Interaction of tobacco mosaic virus and tobacco mosaic virus protein with bovine serum albumin.

Bovine serum albumin (BSA) causes tobacco mosaic virus (TMV) to crystallize at pH values where both have negative charges. The amount of albumin required to precipitate the virus varies inversely with ionic strength of added electrolyte. At pH values above 5, the precipitating power is greatest when BSA has the maximum total, positive plus negative, charge. Unlike early stages of the crystallization of TMV in ammonium sulfate-phosphate solutions, which can be reversed by lowering the temperature, the precipitation of TMV by BSA is not readily reversed by changes in temperature. The logarithm of the apparent solubility of TMV in BSA solutions, at constant ionic strength of added electrolyte, decreases linearly with increasing BSA concentration. This result and the correlation of precipitating power with total BSA charge suggest that BSA acts in the manner of a salting-out agent. The effect of BSA on the reversible entropy-driven polymerization of TMV protein (TMVP) depends on BSA concentration, pH, and ionic strength. In general, BSA promotes TMVP polymerization, and this effect increases with increasing BSA concentrations. The effect is larger at pH 6.5 than at pH 6. Even though increasing ionic strength promotes polymerization of TMVP in absence of BSA, the effect of increasing ionic strength from 0.08 to 0.18 at pH 6.5 decreases the polymerization-promoting effect of BSA. Likewise, the presence of BSA decreases the polymerization-promoting effect of ionic strength. The polymerization-promoting effect of BSA can be interpreted in terms of a process akin to salting-out. The mutual suppression of the polymerization-promoting effects of BSA and of electrolytes by each other can be partially explained in terms of salting-in of BSA.     

The association of Xiphinema diversicaudatum (Micoletsky) with strawberry latent ringspot and arabis mosaic viruses in a raspberry plantation

An outbreak of strawberry latent ringspot virus (SLRV) in a plantation of Mailing Jewel raspberry coincided with the greatest abundance of the nematode vector, Xiphinema diversicaudatum. Arabis mosaic virus (AMV) was not detected in the crop but was, together with SLRV, in many weed species present. AMV was transmitted through the seed of Poa annua, Capsella bursa-pastoris and Senecio vulgaris and SLRV through the seed of Mentha arvensis. X. diversicaudatum were more numerous within the rows than between them and vertical sampling showed that most occurred between 4 and 12 in depth in both locations. Monthly sampling showed that egg laying occurred from April to July; populations increased to a peak in late autumn but declined during the winter, resulting in about a twofold annual increase in numbers. Females, males and juveniles transmitted AMV and SLRV to cucumber seedlings, and in the absence of plants the nematode retained AMV for 112 days and SLRV for 84 days.     

The movement of tobacco mosaic viruses and potato virus X through tomato plants

Tomato aucuba mosaic virus, tobacco mosaic virus and potato virus X took 3'5-4, 5 and 3 days respectively to move from inoculated tomato leaflets into the petioles and stems
On reaching the stem each virus usually first moved downward, but in some plants both upward and downward movement occurred simultaneously and in a few
upward movement occurred first.
All three viruses travelled through the stem at approximately the same rate. Each was capable of travelling more than 80 cm. during the first 12 hr. after entering the stem, giving a minimal average rate of about 8 cm. per hr.
Uninfected pieces of stem invariably occurred between infected pieces. Maximum lengths of stem through which virus particles had apparently passed without causing infection, were 44.5, 49 and 39 cm. for the three viruses.     

Correlation of co-ordinated amino acid substitutions with function in viruses related to tobacco mosaic virus

Sequence data are available for the coat proteins of seven tobamoviruses, with homologies ranging from at least 26% to 82%, and atomic co-ordinates are known for tobacco mosaic virus (TMV) vulgare. A significant spatial relationship has been found between groups of residues with identical amino acid substitution patterns. This strongly suggest that their location is linked to a particular function, at least in viruses identical with the wild-type for these residues. The most conserved feature of TMV is the RNA binding region. Core residues are conserved in all viruses or show mutations complementary in volume. The specificity of inter-subunit contacts is achieved in different ways in the three more distantly related viruses.     

Evolution and replication of tobacco ringspot virus satellite RNA mutants.

The replication properties of linker insertion-deletion mutants of tobacco ringspot virus satellite RNA have been studied by amplification in plants infected with the helper virus. Sequence analysis of the cDNAs corresponding to the replicated forms shows that only one of the original mutated molecules replicates unaltered, and in general new variants accumulate. Depending on the location of the original mutation three types of sequence modifications were observed: (i) deletion of the mutated region followed by sequence duplication, (ii) sequence duplication and deletion outside of the mutated region and (iii) limited rearrangements at the site of mutation. The mutant that replicates without sequence changes accumulates linear multimeric forms suggesting that self-cleavage is affected although the sequence alteration does not involve the hammerhead catalytic domain. Alternative RNA conformations are likely to play a role in the origin of this phenotype and in the formation of sequence duplications. These results demonstrate the great structural flexibility of this satellite RNA.     

Transmission of strains of raspberry ringspot and tomato black ring viruses by Longidorus elongatus (de Man)

Scottish isolates of raspberry ringspot (RRV) and tomato black ring viruses (TBRV) showing slight serological differences were associated in the field with the nematode Longidorus elongatus and were all transmitted equally efficiently by this species in laboratory experiments. Forms of both viruses from southern England and Germany that are distantly serologically related to the Scottish isolates were also transmitted experimentally by L. elongatus, although in the field they are associated with other Longidorus species. L. elongatus transmitted English isolates of RRV almost as efficiently as the Scottish isolates but it transmitted English and German isolates of TBRV only occasionally. Four isolates each of TBRV and RRV were detected by inoculating plants with extracts of nematodes; the results paralleled those of the vector studies.