Institut für Viruskrankheiten der Pflanzen Braunschweig, Germany
Institut für Viruskrankheiten der Pflanzen Braunschweig, Germany
Turnip yellow mosaic virus.
Two major classes of isometric particle, c.
30 nm in diameter with hexagonal
outlines, sedimenting at c.
115 and 54 S and containing respectively c.
35 and 0-2.5% single-stranded RNA. Genomic RNA, M. Wt c.
2 x 106
bottom component (full particles);
sub-genomic coat protein messenger RNA, M. Wt
200,000-300,000, either in top (shells) or bottom component.
Each particle contains 180
molecules of a single coat polypeptide, M. Wt c.
20,000. Thermal inactivation point
65-95°C; longevity in sap a few weeks; concentration in sap often 50-500 mg/l. Host range
usually narrow. Symptoms are mottle or bright yellow mosaic. Virus particles are found in
cytoplasm (full particles and shells), in nuclei
(shells), and rarely in chloroplasts and
mitochondria. Chloroplasts develop small peripheral vesicles bounded by double membranes, and
become rounded and clumped. Transmissible by inoculation with sap; beetle vectors are known for
Recent reviews on tymoviruses are by
Matthews (1977) and
Koenig & Lesemann (1981).
Table 1 lists the definitive members of the group together with some of their properties.
Table 1. Definitive members of the tymovirus group
no. or ref
|Families with species
|Andean potato latent (APLV)
||South American Andes
|Belladonna mottle (BMV)
|Cacao yellow mosaic (CoYMV)
||Africa (Sierra Leone)
||Sterculiaceae, Apocynaceae, Bombacaceae, Chenopodiaceae, Solanaceae
|Clitoria yellow vein (CYVV)
||Leguminosae, Malvaceae, Solanaceae
|Desmodium yellow mottle (DeYMV)
|Dulcamara mottle (DMV)
|Eggplant mosaic (EMV)
||Trinidad, strains in North and South America
|Erysimum latent (ELV)
||Amaranthaceae, Caryophyllaceae, Cruciferae, Labiatae, Leguminosae and Resedaceae
|Kennedya yellow mosaic (KYMV)
|Okra mosaic (OkMV)
||Africa (Ivory Coast, Nigeria)
||23 families including all those listed for the other viruses except Valerianaceae and Caesalpiniaceae
|Ononis yellow mosaic (OYMV)
|Physalis mosaic (PhyMV)
|Plantago mottle (PlMV)
||Plantaginaceae, Aizoaceae, Leguminosae, Scrophulariaceae, Solanaceae
|Scrophularia mottle (ScrMV)
||Scrophulariaceae, Caryophyllaceae, Labiatae, Solanaceae, Umbelliferae and Valerianaceae
|Turnip yellow mosaic (TYMV)
||Phyllotreta spp., Psylliodes spp.
|Wild cucumber mosaic (WCuMV)
(a) Koenig, Fribourg & Jones, 1979;
(b) Gibbs et al., 1966;
(c) Shukla, Proeseler & Schmelzer, 1975;
(d) Peters & Derks, 1974;
(e) Granett, 1973.
Geographical Distribution etc
Tymoviruses have been reported from most parts of the world including tropical, subtropical
and temperate regions. Restricted host ranges
(Table 1), frequently in wild plants, and lack of
vector insects are probably the main reasons for the limited distribution of
Association with Vectors
Several tymoviruses are transmitted by beetles in the families Chrysomelidae and Curculionidae.
The efficiency of transmission is low with some tymoviruses (e.g. ScrMV, APLV) and high with
others (TYMV, BMV). The former viruses may be transmitted by a purely mechanical process
Jones & Fribourg, 1977
whereas the latter may become more intimately associated with
Weidemann & Bode, 1973
The viruses are retained by the insects
for a few hours (ScrMV) up to several days (BMV, TYMV).
A single instance of whitefly transmission of a tymovirus (OkMV) has been reported
(Lana & Taylor, 1976).
No other vectors of biological importance are known.
Tymoviruses are highly infectious and are spread by mechanical contact,
beetle vectors and probably on the bodies of contaminated animals.
True seed transmission has been
recorded for APLV
Most natural host plants are perennials, and this aids the survival
Relations with Cells and Tissues
Tymoviruses invade all main tissues of their host plants. Effects on cells have been studied
almost exclusively in leaf parenchyma tissues. Characteristic changes are induced in the fine
structure of chloroplasts (for reviews see
notably the formation
of small vesicles at the periphery, bounded by double membranes (50-100 nm thick)
which seem to
be continuous with the chloroplast double membrane
(Hatta & Matthews, 1974
Hatta, Bullivant & Matthews, 1973
The vesicles have a narrow neck and often contain fibrils thought to
represent double-stranded nucleic acid. The chloroplasts become clumped and virus particles
accumulate in the cytoplasm. Later in infection the chloroplasts develop large internal
vesicles or vacuoles which may at least in part originate from inflated
The vacuoles may be seen with the light microscope in TYMV-infected
protoplasts; their formation depends on an intact photosynthetic apparatus and
on exposure to
(Matthews & Sarkar, 1976
After the bulk of virus has been produced, further changes
may lead to a more or less complete disorganization of the chloroplasts.
Virus particles are first found in electron-lucent zones which form in the cytoplasm over
the chloroplast vesicles. Virus particles eventually reach high concentrations in the
and the cell vacuoles are also often invaded as a result of breakages of the tonoplast.
seldom, particles are found within chloroplasts and mitochondria
conditions, e.g. wilting or plasmolysis
(Hatta & Matthews, 1974;
form crystalline aggregates in the cytoplasm, nuclei and vacuoles
tymoviruses studied, shells accumulate in the nuclei early in infection
and may later fill a
major part of the nuclear space. They are, however, also present in the cytoplasm
(Hatta & Matthews, 1976;
In addition to the described group-specific cytopathic effects, virus- or strain-specific
changes may be induced which are discussed in detail by
Lesemann (1977) and
Koenig & Lesemann (1981).
Tymoviruses have a single species of coat protein of c.
20,000 M. Wt. The amino
acid composition of tymoviruses (H. L. Paul, A. J. Gibbs & B. Wittmann-Liebold, unpublished
results) and the complete amino acid sequence of TYMV
(Peter et al., 1972
The protein shells are T
= 3 icosahedral structures containing 180 protein subunits
clustered into 12 pentamers and 20 hexamers
(Klug, Longley & Leberman, 1966
density gradients, two major and in some instances several minor components are separated.
The biological significance of the minor components is uncertain
of the major bottom component sedimenting at c.
115 S contain
one molecule of
single-stranded RNA of M. Wt 2 x 106
which accounts for about 35% of the particle
weight. In TYMV the bottom component
(Szybiak, Bouley & Fritsch, 1978
also contains a
sub-genomic RNA of M. Wt c.
0.25 x 106
which acts as
coat protein messenger
(Klein et al., 1976
Pleij et al., 1976
The major top component sedimenting
54 S contains no RNA in TYMV and coat protein mRNA in EMV, OkMV and WCuMV
(Szybiak et al., 1978
The top component of EMV also contains transfer RNA species
of plant origin
(Pinck & Hall, 1978
Spermidine and spermine account for 1% and less than
0.04%, respectively, of the particle weight of TYMV
(Beer & Kosuge, 1970
and may be
important in neutralizing some of the phosphate groups of the RNA.
Particles of tymoviruses are stabilized by hydrophobic protein-protein interactions
which are stronger in TYMV than in EMV
(Jonard et al., 1976;
Bouley, Briand & Witz, 1977).
The presence of RNA destabilizes the protein-protein interactions
(Jonard et al., 1976;
Bouley et al., 1977)
and leads to conformational changes in the protein
(Tamburro et al., 1978).
Protein-RNA interactions probably involve hydrogen bonds
between protein carboxylate and nucleotide amino groups
Jonard et al., 1976).
In attempts to reassemble nucleic acid-containing particles of TYMV in vitro,
virus-like protein-RNA complexes were obtained at low pH in the presence of magnesium or
spermidine but these were unstable at neutral pH
(Jonard et al., 1976).
were also obtained with TYMV protein and RNA species from EMV or BMV, but not with RNA from
tobacco mosaic virus
(Bouley et al., 1975).
The reported base compositions of tymovirus RNA species are within the range of G 15.2-17.5 :
A 17.0-23.8 : C 31.9-42.1 : U 22.1-29.4. Cytidine is always the most common nucleotide.
The nucleotide sequence of the genomic RNA of M. Wt 2 x 106 encodes all the
information for viral infectivity, and includes the cistron for the coat protein, which is
located at its 3' extremity. In cell-free systems the genomic RNA directs the synthesis of
one or more large proteins, but not of viral coat protein. This is done by the sub-genomic
viral coat protein messenger RNA of M. Wt c. 0.25 x 106 which is derived
from the genomic RNA in vivo in an unknown way
(Klein et al., 1976;
Pleij et al., 1976;
Ricard et al., 1977;
Szybiak et al., 1978).
The entire nucleotide
sequence is known for the coat protein messenger RNA of TYMV
(Guilley & Briand, 1978);
the sequence of 567 nucleotides in the coat protein cistron predicts the amino acid sequence
actually found by
Peter et al. (1972).
The genomic and sub-genomic RNA molecules both
have 5' terminal 7-methylguanosine
(Briand, Keith & Guilley, 1978)
and both have at their
3' ends a non-translated sequence of 109 nucleotides which can act as a
substrate for various
tRNA-specific enzymes, including valyl-tRNA synthetase
(see Briand et al., 1977, for
review). Both RNA molecules have the same base composition
(Guilley & Briand, 1978).
The small vesicles induced by tymoviruses in the periphery of chloroplasts contain
membrane-bound viral replicase
(Laflèche et al., 1972
and are probably the
main site of production of viral plus-strand RNA. Various aspects of TYMV replication have
been discussed in detail by
Hatta & Matthews (1976)
Relationships within the Taxon
Tymoviruses have been classified according to RNA base composition
(Gibbs et al., 1966
protein amino acid composition (H. L. Paul, A. J. Gibbs & B. Wittmann-Liebold, unpublished
results). Serologically, several tymoviruses are closely related and some might be regarded as
strains of the same virus, e.g. OYMV and PlMV as strains of ScrMV, APLV as a strain of EMV,
and DMV as a strain of BMV
Perhaps all the tymoviruses isolated
from solanaceous hosts, i.e. the many different strains of APLV, EMV, PhyMV, BMV and DMV,
might be considered as strains of one virus. The divergent views on this question have been
Koenig & Lesemann (1981)
Affinities with Other Groups
No close affinities of tymoviruses with viruses in other groups are known. It is not known
whether or not the weak serological cross reactivities of several tymoviruses with
cocksfoot mild mosaic
reflect true relationships or chance similarities
(Bercks & Querfurth, 1972
- Beer & Kosuge, Virology 40: 930, 1970.
- Bercks & Querfurth, Phytopath. Z. 75: 215, 1972.
- Bouley, Briand, Jonard, Witz & Hirth, Virology 63: 312, 1975.
- Bouley, Briand & Witz, Virology 78: 425, 1977.
- Briand, Jonard, Guilley, Richards & Hirth, Eur. J. Biochem. 72: 453, 1977.
- Briand, Keith & Guilley, Proc. natn. Acad. Sci. U.S.A. 75: 3168, 1978.
- Gibbs, Hecht-Poinar, Woods & McKee, J. gen. Microbiol. 44: 177, 1966.
- Granett, Phytopathology 63: 1313, 1973.
- Guilley & Briand, Cell 15: 113, 1978.
- Hatta, Virology 69: 237, 1976.
- Hatta & Matthews, Virology 59: 383, 1974.
- Hatta & Matthews, Virology 73: 1, 1976.
- Hatta, Bullivant & Matthews, J. gen Virol. 20: 37, 1973.
- Jonard, Briand, Bouley, Witz & Hirth, Phil. Trans. R. Soc. Ser. B 276: 123, 1976.
- Jones & Fribourg, Ann. appl. Biol. 86: 123, 1977.
- Kaper, The Chemical Basis of Virus Structure, Dissociation and Reassembly, Amsterdam: North Holland, 485 pp., 1975.
- Klein, Fritsch, Briand, Richards, Jonard & Hirth, Nucleic Acids Res. 3: 3043, 1976.
- Klug, Longley & Leberman, J. molec. Biol. 15: 315, 1966.
- Koenig, Virology 72: 1, 1976.
- Koenig & Lesemann, in Handbook of Plant Virus Infections and Comparative Diagnosis, p. 33, ed. Kurstak, Amsterdam: Elsevier/North-Holland, 1981.
- Koenig, Fribourg & Jones, Phytopathology, 69: 748, 1979.
- Laflèche, Bové, Dupont, Mouchés, Astier, Gamier & Bové, in Proc. 8th Meet. Fed. Eur. biochem. Soc., Amsterdam 1972, pp. 43-71, Amsterdam: North-Holland, 1972.
- Lana & Taylor, Ann. appl. Biol. 82: 361, 1976.
- Lesemann, Phytopath. Z. 90: 315, 1977.
- Matthews, A. Rev. Phytopath. 11: 147, 1973.
- Matthews, in The Atlas of Insect and Plant Viruses, p. 347, ed. K. Maramorosch, New York: Academic Press, 1977.
- Matthews & Sarkar, J. gen. Virol. 33: 435, 1976.
- Peter, Stehelin, Reinbolt, Collot & Duranton, Virology 49: 615, 1972.
- Peters & Derks, Neth. J. Pl. Path. 80: 124, 1974.
- Pinck & Hall, Virology 88: 281, 1978.
- Pleij, Neeleman, Van Vloten-Doting & Bosch, Proc. natn. Acad. Sci. U.S.A. 73: 4437, 1976.
- Ricard, Barreau, Renaudin, Mouchés & Bové Virology 79: 231, 1977.
- Shukla, Proeseler & Schmelzer, Acta phytopath. Acad. Sci. hung. 10: 211, 1975.
- Szybiak, Bouley & Fritsch, Nucleic Acids Res. 5: 1821, 1978.
- Tamburro, Guantieri, Piazzolla & Gallitelli, J. gen. Virol. 40: 337, 1978.
- Walters, Adv. Virus Res. 15: 339, 1969.
- Weidemann & Bode, Phytopath. Z. 76: 6, 1973.
The authors work on tymoviruses was supported by the Deutsche Forschungsgemeinschaft.
Serological classification of tymoviruses on the basis of average serological
differentiation indices (SDI) in reciprocal tests. The SDI is the number of two-fold dilution
steps separating heterologous and homologous titres of an antiserum. The average SDI of
reciprocal tests are depicted as length units. The scheme is based on more than 4000
individual titre determinations with 321 bleedings from 56 rabbits. For details see