A structural comparison of concanavalin a and tomato bushy stunt virus protein

Summary Significant structural equivalence has been found among the polypeptide folds of the two tomato bushy stunt virus (TBSV) subunit domains and concanavalin A. This suggests gene duplication in the TBSV coat protein and leads to speculation on common functional properties of concanavalin A and viral coat proteins.Non-standard abbreviations TBSV tomato bushy stunt virus - SBMV southern bean mosaic virus     

Chloroplast alterations induced by tomato bushy stunt virus inDatura leaves

Summary Peculiar chloroplast alterations were found in mesophyll cells ofDatura stramonium systemically infected with tomato bushy stunt virus. These alterations lead to complete rearrangement of the thylakoids.     

THE INFLUENCE OF LIGHT INTENSITY ON THE SUSCEPTIBILITY OF PLANTS TO CERTAIN VIRUSES

Reducing the light intensity under which plants were grown in summer to one-third increased their susceptibility to infection with tobacco necrosis, tomato bushy stunt, tobacco mosaic and tomato aucuba mosaic viruses. With the first two viruses shading increased the average number of local lesions per leaf by more than ten times and by more than five times with the second two.
Reducing the light intensity increased the virus content of sap from leaves inoculated with Rothamsted tobacco necrosis virus by as much as twenty times. As it also reduced the total solid content of sap by about one-half, purification was greatly facilitated; crystalline preparations of the virus were readily made from shaded plants but not from unshaded controls.
Reducing the light intensity also increased the virus content of systemically infected leaves; the greatest effect was with tomato bushy stunt virus with which increases of up to ten times were obtained, but with tobacco mosaic and aucuba mosaic viruses there were also significant increases.
The importance of controlled illumination in raising plants for virus work and the possible mechanisms responsible for the variations in susceptibility are discussed.     

HEAT-THERAPY OF VIRUS-INFECTED PLANTS

Virus-free plants were produced from parents systemically infected with the following five viruses: tomato bushy stunt, carnation ring spot, cucumber mosaic, tomato aspermy and Abutilon variegation. The leaves formed while the infected plants were kept at 36°C. were free from symptoms, and test plants inoculated from these remained uninfected. When cuttings were taken from the infected plants at the end of the treatment most grew into healthy plants. The treated plants themselves usually developed symptoms after varying lengths of time at 20°C, but some that before treatment were infected with tomato aspermy, cucumber mosaic or Abutilon variegation viruses, remained permanently healthy.
The same method failed to cure plants infected with tomato spotted wilt, potato virus X and tobacco mosaic virus, although it decreased their virus content. Heat-therapy seems not to be correlated with the thermal inactivation end point of the virus in vitro.     

Purification,electron microscopy and serology of virus isolated fromEuonymus europaea

“Euonymus mosaic virus”, purified from cucumber cotyledons by the differential and density-gradient centrifugation, shows typical nucleoprotein absorption spectrum. Electron microscopy reveals isometric virus particles of about 37 nm diameter. No reaction of purified “Euonymus mosaic virus” was observed with antisera against a raspberry ringspot virus, tobacco ringspot virus, cherry leaf roll virus, strawberry latent ringspot virus, tomato ringspot virus, elm mosaic virus, arabis mosaic virus, tomato bushy stunt virus and watermelon mosaic virus.     

Protein interfaces and intersubunit bonding. The case of tomato bushy stunt virus.

An atomic model of the subunit of tomato bushy stunt virus (TBSV) has been constructed to fit an electron density map at 2.9 A resolution. Subunit interfaces show networks of polar residues forming H-bonds and salt bridges. The way in which alternative specific bonding geometries are built into a contact are described.     

Divalent cation sites in tomato bushy stunt virus. Difference maps at 2-9 A resolution

Difference electron density maps, using as few as four 1/2 degrees oscillation photographs, have been computed for tomato bushy stunt virus crystals soaked in EDTA. GdCl3 and silicotungstate. The maps define a double divalent cation site, responsible for regulating expansion of the virus particle, as well as sites for binding tungstate anions.     

Structure and assembly of turnip crinkle virus. I. X-ray crystallographic structure analysis at 3.2 A resolution

The structure of turnip crinkle virus has been determined at 3.2 A resolution, using the electron density of tomato bushy stunt virus as a starting point for phase refinement by non-crystallographic symmetry. The structures are very closely related, especially in the subunit arm and S domain, where only small insertions and deletions and small co-ordinate shifts relate one chain to another. The P domains, although quite similar in fold, are oriented somewhat differently with respect to the S domains. Understanding of the structure of turnip crinkle virus has been important for analyzing its assembly, as described in an accompanying paper.     

A defective interfering RNA that contains a mosaic of a plant virus genome

A symptom-modulating RNA associated with tomato bushy stunt virus (TBSV) was investigated with respect to physical and biological properties. Linear RNA of approximately 396 nucleotides was packaged in viral coat protein and was dependent on TBSV for replication. Coinoculation of the small RNA with TBSV resulted in the attenuation of TBSV-induced symptoms and depression of virus synthesis in whole plants. Nucleotide sequence analysis revealed that the symptom-modulating RNA was derived from 5', 3', and internal segments of the TBSV genome. The identification of this symptom-modulating RNA as a co-linear deletion mutant of the helper virus genome establishes it as the first definitive defective interfering RNA (DI RNA) to be identified in association with a plant virus.     

Tomato bushy stunt virus (TBSV) infecting Lycopersicon esculentum

Tomato bushy stunt virus (TBSV) was detected in tomato crop (Lycopersicon esculentum) in Egypt with characteristic mosaic leaf deformation, stunting, and bushy growth symptoms. TBSV infection was confirmed serologically by ELISA and calculated incidence was 25.5%. Basic physicochemical properties of a purified TBSV Egh isolate were identical to known properties of tombusviruses of isometric 30-nm diameter particles, 41-kDa coat protein and the genome of approximately 4800 nt. This is the first TBSV isolate reported in Egypt. Cloning and partial sequencing of the isolate showed that it is more closely related to TBSV-P and TBSV-Ch than TBSV-Nf and TBSV-S strains of the virus. However, it is distinct from the above strains and could be a new strain of the virus which further confirms the genetic diversity of tombusviruses.     

Nematode transmissibility of pseudo-recombinant isolates of tomato black ring virus

Pseudo-recombinant isolates of tomato black ring virus (TBRV), containing RNA-i of the potato bouquet serotype and RNA-2 of the beet ring-spot serotype, were transmitted by the nematode Longidorus elongatus, which also transmits the beet ringspot serotype but not the potato bouquet serotype. Transmissibility by L. elongatus was correlated with antigenic specificity of the virus particles, providing further evidence that nematode transmissibility depends on the structure of the virus coat protein. The distribution of genetic determinants for biological properties between the RNA-1 and RNA-2 of TBRV resembles that for raspberry ringspot virus.     

Encapsidation of turnip crinkle virus is defined by a specific packaging signal and RNA size.

A protoplast infection assay has been used to reliably examine the viral RNA encapsidation of turnip crinkle virus (TCV). Analysis of the encapsidation of various mutant viral RNAs revealed that a 186-nucleotide (nt) region at the 3' end of the coat protein (CP) gene, with a bulged hairpin loop of 28 nt as its most essential element, was indispensable for TCV RNA encapsidation. When RNA fragments containing the 186-nt region were used to replace the CP gene of a different virus, tomato bushy stunt virus, the resulting chimeric viral RNAs were encapsidated into TCV virions. Furthermore, analysis of the encapsidated chimeric RNA species established that the RNA size was an important determinant of the TCV assembly process.     

Enhanced competitiveness of tomato bushy stunt virus defective interfering RNAs by segment duplication or nucleotide insertion.

We have analyzed atypical tomato bushy stunt virus defective interfering (DI) RNA species which accumulated during a passage series in protoplasts. We present a rationale for the order of appearance of these molecules and show, using competition assays, that either segment duplication or single nucleotide insertion can enhance DI RNA competitiveness. Possible mechanisms for the introduction of the modifications observed in these DI RNAs are discussed.     

Studies on the occurrence of tomato bushy stunt virus in English rivers

Tomato bushy stunt virus (TBSV) of unknown source was isolated from water of the River Thames, near Oxford. The isolate designated TBSV-T was mechanically transmissible to several tomato (Lycopersicon esculentum) cvs and to other species including Petunia hybrida, pepper (Capsicum annuum). eggplant (Solanum melongena), Nicotiana clevelandii, Chenopodium amaranticolor and C. quinoa in which it caused systemic symptoms. It caused no infection of globe artichoke (Cynara scolymus) or Pelargonium domesticum. The virus was not adsorbed to soil and could be isolated from leachate of soil in which systemically-infected tomato or C. quinoa plants were grown. Tomato plants became infected when grown in soil watered with virus suspensions. TBSV-T was infective after 10 min at 80°C but not at 90°C and when diluted to 10^-5 but not to 10^-6. Purified virus preparations contained C. 30 nm isometric particles. In gel-diffusion serological tests, TBSV-T reacted with homologous anti-serum and with antiserum to petunia asteroid mosaic virus but not to pelargonium leaf curl virus. Seed-borne infection (50–65%) of TBSV was demonstrated in plants grown from seed of symptomlessly-infected tomato fruit. TBSV was isolated from symptomlessly-infected tomato fruit imported from Morocco during October-April 1981. One of the isolates (TBSV-M) was indistinguishable from TBSV-T in host range, symptomatology and serological reactions. TBSV was also found in tomato plants growing extraneously in primary settlement beds at sewage works; such plants having been derived from undigested seeds in sewage. Because of its ‘alimentary-resistance’ in man, it is possible that one ecological route whereby TBSV enters rivers is by man's consumption of TBSV-infected tomatoes and eventual sewage dispersal into rivers.     

Identification of alfalfa mosaic virus and tomato bushy stunt virus in hop (Humulus lupulus L.) and grapevine (Vitis vinifera subsp.sativa (DC./HEGI) plants in czechoslovakia

In agreement with the results of biological tests with transmission to herbaoeous indicators and on orientation electron microscopic investigation, alfalfa mosaic virus (AMV) and tomato bushy stunt virus (TBSV) were serologically identified in the leaves of some of 8 samples of hop plants and of 17 bushes of grapevine, showing a complex of symptoms described in this paper. The latter reacted in double gel diffusion tests toPetunia strain but not to artichoke strain. The identification of these two viruses in grapevine is the first finding in Czechoslovakia, whereas in hop it is probably the first finding anywhere.     

Structure of tomato bushy stunt virus: V. Coat protein sequence determination and its structural implications

We report the chemically determined sequence of most of the polypeptide chain of the coat protein of tomato bushy stunt virus. Peptide locations have been determined by comparison with the high-resolution electron density map from X-ray crystallographic analysis as well as by conventional chemical overlaps. Three small gaps remain in the 387-residue sequence. Positively charged side-chains are concentrated in the N-terminal part of the polypeptide (the R domain) as well as on inward-facing surfaces of the S domain. There is homology of S-domain sequences with structurally corresponding residues in southern bean mosaic virus.