Turnip yellow mosaic virus
R. E. F. Matthews
Department of Cell Biology, University of Auckland, New Zealand
Markham & Smith (1949).
- Brassicavirus octahedron (Rev. appl. Mycol. 38: 677)
An RNA-containing virus with isometric particles about 28 nm in diameter. Host range is
confined almost entirely to the Cruciferae. It has been reported from several areas of Western
Europe. It may reach high concentrations in infected leaves, is readily sap transmissible, and
is transmitted in the field by flea beetles.
Causes a mosaic disease in various Brassica
Host Range and Symptomatology
Host range is confined almost entirely to the Cruciferae. Transmissible by inoculation of
sap to many species in this family
(Broadbent & Heathcote, 1958
- There is no definitive diagnostic species. Many strains give a bright yellow
mosaic in Brassica pekinensis (Chinese cabbage)
but others give much milder
Non-hosts include Chenopodium amaranticolor, Cucumis sativus, Nicotiana
tabacum and Phaseolus vulgaris.
- Chinese cabbage is a good species for maintaining cultures and as starting
material for virus
purification. Growing temperatures in the range 20-25°C are best. Above 25°C
virus are less.
- There is no reliable local lesion host. Most strains produce chlorotic local lesions in
cabbage, their distinctness depending on the growing conditions. They appear most
when plants are inoculated young and then kept in artificial light of 8000 lux (or more) at
15-20°C. At 25°C or above lesions are much less distinct. Some strains, particularly
those isolated from white areas in the mosaic, produce necrotic local lesions in
These are most distinct at 15-20°C.
StrainsThe Cambridge culture
(Markham & Smith, 1949
Stock cultures of the virus originating
from Cambridge, England, consist of a mixture of closely related strains. Areas of
in leaves showing mosaic contain different strains of the virus
It is not possible to
isolate and maintain a pure culture of a single strain; single lesion isolates soon
revert to a
mixture like the original stock culture.
The Northumberland isolate
(Broadbent & Heathcote, 1958).
This isolate is serologically
distinguishable from the above culture, and causes less severe symptoms in most hosts,
more severe ones in cauliflower, cabbage and brussels sprout.
Groups of strains. Strains isolated from various places in Western Europe and
the basis of coat protein and RNA composition fell into two clearly defined groups
(Symons et al., 1963).
They were distinguished particularly by differences in the cytidylic acid content
of their RNA (averaging 38.2% in group 1 and 41.6% in group 2).
Transmission by Vectors
Transmitted by various biting insects
(Markham & Smith, 1949
The most important in
natural transmission are probably the flea beetles (species of Phyllotreta
). These become infective after a few minutes feeding and then infect
plants by feeding for only a few minutes. The mustard beetle Phaedon cochleariae
its larvae also transmit. Larvae acquired virus in 1-3 minutes feeding. There was a
about one day before they could infect. Ability to transmit was not retained through the pupal
stage. Transmission by these and other leaf-eating insects is probably a purely mechanical
Transmission through Seed
None recorded. Further tests are needed.
Transmission by Dodder
The nucleoprotein is strongly immunogenic in rabbits, the empty protein shells much less so.
Precipitation tests in tubes, or immunodiffusion in agar give satisfactory results.
subunit of the virus shell does not cross react in precipitation tests with antiserum prepared
against the intact viral shell.
Distantly serologically related to
wild cucumber mosaic virus
(McLeod & Markham, 1963
and to cacao yellow mosaic virus
(Brunt et al., 1965
Stability in Sap
In Chinese cabbage sap (pH = c.
6.0) some infectivity is retained after 10 min at
70°C but not at 75°C. Heat inactivation is much more rapid at pH 7.5 than at pH 6.0.
At pH 6-7 infectivity decreases over a period of weeks either at room temperature or at 4°C.
Dilution end-point in sap from fully infected plants is usually between 10-4
The virus is readily isolated in good yield (0.5-2.0 mg/g fresh wt) from Chinese cabbage
plants by either the ethanol-ammonium sulphate method of
Markham & Smith (1949)
or the pH
4.8 method of
The ethanol-ammonium sulphate procedure is convenient for large
scale preparations of the virus: care must be taken to keep the temperature below about
while the virus is in contact with 30% ethanol. The pH 4.8 procedure is convenient for small
scale preparations, especially where several are made simultaneously. Purified virus
preparations can be fractionated into various classes of particle by centrifugation in CsCl
density gradients. The virus crystallizes as octahedra from one-third saturated ammonium
Properties of Particles
Purified preparations contain two major classes of particles, empty protein shells without
RNA (T) and the infective nucleoprotein (B1
Sedimentation coefficients (s20, w) at infinite dilution (svedbergs):
Molecular weights (daltons): 3.6 x 106(T), 5.4 x 106(B1).
Diffusion coefficients (D20 x 10-7 cm2/sec): 1.51(T),
Isoelectric points: pH 3.75 (T and B1).
Partial specific volumes: 0.733(T), 0.661(B1).
Absorbances at 260 nm (1 mg/ml, 1 cm light path): 0.96(T), 9.6(B1).
A260/A280: 0.81(T), 1.51(B1).
Buoyant densities in CsCl (g/ml): 1.29(T), 1.42(B1).
Fractionation of purified preparations in CsCl density gradients yields at least
nucleoprotein fractions besides T and B1. Fraction B2 has about
RNA content as B1 but has a higher buoyant density in CsCl. Fraction B0
has about two-thirds and B00 about one-third as much RNA as the intact virus. These
three fractions are present to the extent of about 1-3% of B1. None of them is
infective; nor do they enhance the infectivity of B1
(Faed & Matthews, unpublished).
Icosahedral symmetry, about 28 nm in diameter. Built of 180 protein subunits clustered into
20 hexamers and 12 pentamers
(Finch & Klug, 1966
Electron micrographs of negatively
stained virus show 32 morphological subunits
with which the RNA is in part associated.
Detailed arrangement of the RNA within the protein shell not known
Molecular weight about 1.9 x 106
; 34% by weight of particle,
single-stranded; may be in the form of a closed loop in the infective virus. Molar
percentages of nucleotides for type strain:
G17.2, A22.4, C38.3, U22.1. s20, w
= 21.8 S in 0.01 M Tris buffer
pH 7.5. RNA appears to be in one piece; a single break abolishes infectivity. A base-paired,
double-stranded, ribonuclease-resistant form of the viral RNA can be isolated from infected
Protein: 66% of particle by weight. Probably only one kind of protein in the particle.
189 amino acid residues per subunit of molecular weight = 20,000 for the type strain
(Symons et al., 1963).
For amino acid composition, see
Symons et al. (1963),
Harris & Hindley (1965).
Other components; A polyamine, probably spermidine, is present (about 0.7% by
of particle). No enzyme or lipid in particle.
Relations with Cells and Tissues
Virus is present in all tissues of Chinese cabbage including the apical meristem region,
but reaches highest concentration in the leaf lamina. However, dark green islands in the
contain little or no virus and are essentially normal cytologically. In mesophyll cells
containing virus, chloroplasts become rounded and clumped to form X-bodies
(Chalcroft & Matthews, 1966
Electron microscopy reveals a variety of abnormalities in such
chloroplasts depending on strain of virus and time after infection. The most constant feature
is the appearance of numerous vesicles of variable size in the chloroplast, particularly near
its surface. Site of virus synthesis is not established, but mature virus particles accumulate
in the cytoplasm. A virus-specific RNA polymerase is reported from infected leaves.
a rod-shaped virus, may cause similar macroscopic symptoms in turnip and
Chinese cabbage but does not cause the chloroplast abnormalities characteristic of turnip
yellow mosaic virus infection.
mechanically and by flea beetles and have similar stability in vitro.
virus has a similar host range largely confined to the Cruciferae and both viruses may cause
rather similar symptoms in these hosts. However, these two viruses are not related to each
other or to turnip yellow mosaic virus
(Broadbent & Heathcote, 1958
Symons et al., 1963
and the particles of both turnip crinkle and rosette viruses sediment as a single
component. Extracts from leaves infected with turnip yellow mosaic virus give a characteristic
pattern on sedimentation in the analytical ultracentrifuge
For a comprehensive review of turnip yellow mosaic virus, see
Matthews & Ralph (1966).
- Broadbent & Heathcote, Ann. appl. Biol. 46: 585, 1958.
- Brunt, Kenten, Gibbs & Nixon, J. gen. Microbiol. 38: 81, 1965.
- Chalcroft & Matthews, Virology 28: 555, 1966.
- Finch & Klug, J. molec. Biol. 15: 344, 1966.
- Harris & Hindley, J. molec. Biol. 13: 894, 1965.
- Kaper, J.M. (1968) in Molecular Basis of Virology, Am. chem. Soc. Monograph 164, p.1, Ed. H. Fraenkel-Conrat, New York: Reinhold.
- McLeod & Markham, Virology 19: 190, 1963.
- Markham & Smith, Parasitology 39: 330, 1949.
- Matthews, Virology 12: 521, 1960.
- Matthews & Ralph, Adv. Virus Res. 12: 273, 1966.
- Symons, Rees, Short & Markham, J. molec. Biol. 6: 1, 1963.
Leaf of Chinese cabbage showing mosaic caused by Cambridge stock culture.
(Photo J. Endt.)
Strains isolated from different islands of tissue in leaves containing the
Cambridge stock culture: top left, healthy; top right, pale green; bottom left,
yellow green; bottom right, white. (Photo J. Endt.)
Octahedral crystals formed in one-third saturated ammonium sulphate solution.
(x 77). (Photo courtesy of R. Markham.)
Electron micrograph of a thin section through an infected Chinese cabbage cell,
showing clumping and rounding of chloroplasts (C), and the presence of numerous
vacuoles (V), especially near the surface of the chloroplasts. Bar represents 1
µm. (Photo courtesy of R. Ushiyama.)
Particles negatively stained in phosphotungstate and showing clusters of subunits.
Bar represents 50 nm. (Photo courtesy of S. Bullivant.)
Schlieren patterns: Upper: sedimentation of crude extract from infected Chinese
cabbage leaves, showing B1 (virus nucleoprotein), 83 S ribosomes and T
(empty virus protein shells)
Lower: extract from healthy leaves showing 83 S ribosomes and 68 S