Single amino acid substitution in 30K protein of TMV defective in virus transport function

The nucleic acids of many plant viruses encode proteins with one or more of the following properties: an Mr of approximately 30000, localization in the cell wall of the infected plant and a demonstrated role in cell-tocell transport of infection. A progressive alignment strategy, aligning first those sequences known to be similar, and then aligning the resulting groups of sequences, was used to examine further the relatedness of the amino acid sequences of putative transport proteins of caulimoviruses, of proteins similar to the putative transport protein of alfalfa mosaic virus (AIMV) and of those similar to the tobacco mosaic virus (TMV) 30K protein. The strategy first identified regions in which multiple dipeptides of one group were similar to those of another group. The regions of similarity were brought into alignment by the conservative introduction of gaps. The positions of the introduction of gaps were adjusted to optimize similarity.Statistical significances of the resulting alignments, determined both by comparison with shuffled amino acid sequences and with the sequence alignment off-set by 1 to 15 residues in each direction, suggest that the amino acid sequences of the three groups of viruses are distantly related. Nevertheless, significant relationships between members of the caulimoviral group of sequences and members of each of the AIMV-like and TMV-like groups were found. These relationships and the analysis of the number of insertions/deletions between present sequences and a hypothetical common ancestor suggest that the sequences of the caulimoviral proteins are less diverged from the ancestor than either the AIMV-like or TMV-like proteins. The alignment identified common regions of predicted secondary structure and regions of similar hydropathy, regions possibly crucial for proper functioning of the proteins.

Section: Methodsmentioning

confidence: 99%

Similarities Between Putative Transport Proteins of Plant Viruses

Melcher

1990

“…There is as yet no direct biochemical evidence to suggest a specific function for the 3A proteins of these tripartite viruses. In contrast, there is a 0000-8307 growing body of evidence which indicates that the non-structural p30 protein of tobacco mosaic virus (TMV) is involved in the cell-to-cell movement of viral RNA (Leonard & Zaitlin, 1982;Ohno et al, 1983;Zimmern & Hunter, 1983). The p30 protein is, however, not homologous to the 3A proteins of A1MV, BMV or CMV, and its sequence varies quite significantly between different strains of TMV (Meshi et al, 1982;Zimmern, 1983).…”

Section: Introductionmentioning

confidence: 99%

Ultrastructural Location of Non-structural Protein 3A of Cucumber Mosaic Virus in Infected Tissue Using Monoclonal Antibodies to a Cloned Chimeric Fusion Protein

MacKenzie

Tremaine

1988

SUMMARYCloned DNA representing the sequence coding for the non-structural protein 3A from cucumber mosaic virus (CMV) was inserted in an expression vector containing a truncated portion of the Protein A gene from Staphylococcus aureus. Expressed fusion protein was purified from Escherichia coli cell extracts by affinity chromatography on rabbit gamma globulin-conjugated Sepharose and used as an immunogen for the production of monoclonal antibodies (MAbs). Five MAbs that reacted with pXCM3AI3 fusion protein in solid phase ELISA were able to immunoprecipitate specifically protein 3A from mixtures of in vitro translation products of CMV RNA. None of these antibodies reacted with the analogous protein in translation products of brome mosaic virus RNA, but all of them reacted with the 3A protein from tomato aspermy virus. Immunogold labelling of ultrathin sections of CMV-infected tobacco tissue with MAb 3H12 demonstrated that the 3A protein accumulated within the nucleoli of these cells. This location differs from that of the analogous 3A protein of alfalfa mosaic virus which is associated with the middle lamella of the cell walls of infected tobacco cells.

“…The Mr of the protein corresponding to the M r 43000 protein of the O strain, which is located on the outside of the outer capsid, was 44000 in the S strain. The implication of the differences in the RNA and protein components between the S and O strains is discussed.Mutants and variants have provided some of the most promising materials for comparative studies of the mechanisms of biological functions of viruses, such as the pathological disorders they induce and their transmissibilities (Nishiguchi et al, 1985;Ohno et al, 1983). Since none of the viruses belonging to the plant reovirus group can be cloned by single local lesion selection, the isolation of mutants of these viruses has generally been considered to be difficult.…”

mentioning

confidence: 99%

Changes in a Nucleic Acid and a Protein Component of Rice Dwarf Virus Particles Associated with an Increase in Symptom Severity

Kimura

Minobe

Omura

1987

SUMMARYRepeated selection of plants with unusually severe symptoms after their inoculation by insect vectors which had been injected with dilute inoculum from crude extracts of a stock culture (O strain) of rice dwarf virus (RDV) resulted in the emergence of a severe isolate (S strain). Of the 12 segments of RDV RNA, the fourth largest RNA of the S strain had an apparent Mr about 20000 larger than that of the corresponding segment of the O strain. The Mr of the protein corresponding to the M r 43000 protein of the O strain, which is located on the outside of the outer capsid, was 44000 in the S strain. The implication of the differences in the RNA and protein components between the S and O strains is discussed.Mutants and variants have provided some of the most promising materials for comparative studies of the mechanisms of biological functions of viruses, such as the pathological disorders they induce and their transmissibilities (Nishiguchi et al., 1985;Ohno et al., 1983). Since none of the viruses belonging to the plant reovirus group can be cloned by single local lesion selection, the isolation of mutants of these viruses has generally been considered to be difficult. However, mutants that lost transmissibility by the insect vector were obtained with clover wound tumour virus (Black et al., 1958) and rice dwarf virus (RDV) (Kimura, 1976a;Minobe et al., 1983).During the course of infectivity assays of purified preparations of RDV from infected rice leaves, a few rice plants showed unusually severe stunting which suggested that a severe strain of RDV had been selected. All the plants had been inoculated by injected insects. This severe (S) strain was selected from the ordinary (O) strain in the present investigation in order to study any deviation in the RNAs and component proteins from those of the O strain.RDV was maintained and propagated in rice plants (Oryza sativa L., cultivar Norin No. 29) which were inoculated by the viruliferous leafhopper, Nephotettix cincticeps.Severe symptoms, as judged by exceptionally short plant height, appeared with very low frequency when rice seedlings were inoculated by insects injected with purified preparations (Kimura, 1976b) of the O strain. Leaves showing the severest symptoms were macerated in four times their weight of 0.1 M-sodium phosphate buffer (pH 7.3), and the slurry was clarified in a Hitachi 20PR centrifuge at 1470 g for 15 min. The supernatant fluid was diluted 103-fold and used as the inoculum for the selection test. Second instar nymphs were each injected in the abdomen 2 weeks after hatching with about 0.2 ~tl of inoculum using a glass capillary with a 50 Ixm tip diameter. Injected insects were confined individually in glass test tubes each of which contained three healthy rice seedlings and 5 ml tap water. The exposed rice plants were replaced with new seedlings at intervals of a week and the exposed plants were transplanted to a greenhouse where they were observed for expression of symptoms for 60 days. The selection process was repeated 10 more times.S...