Pathogen Profiles

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Molecular Plant Pathology - Pathogen Profiles

Potato leafroll virus: a classic pathogen shows some new tricks

Michael Taliansky, Mike A. Mayo and Hugh Barker

Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, UK

Taxonomy: PLRV is the type species of the genus Polerovirus, in the family Luteoviridae. Isolates are known from most continents, presumably all spread in potato material derived from the Andean region of South America.
Physical Properties: PLRV particles are isometric and c. 25 nm in diameter. They contain one major (c. 23 kDa) and one minor (c. 80 kDa) protein. The genome is a single 5.8 kb positive sense RNA that has neither a 5'-cap nor 3' poly(A) but carries a VPg.
Host Range: PLRV has a limited host range; about 20 largely solanaceous species have been infected experimentally. PLRV is a common pathogen of potato, and closely related isolates are occasionally found in tomato, but no other crops are affected.
Disease symptoms: Infection, especially from infected seed potato stocks, causes leafrolling and stunting, the extent depending on the potato cultivar.
Biological properties:  The biology of PLRV is that of a classic luteovirus. Its isometric particles are persistently transmitted by aphids in a non-propagative manner, it multiplies largely in phloem tissue and disease symptoms reflect this localization. A decade or so of molecular study has revealed the many features of PLRV that are characteristic of its family.
Key attractions: In recent years some interesting features of PLRV have emerged that are the focus of further investigation. These are, its phloem confinement, its movement in infected plants, its ability to suppress gene silencing and new ideas about the structure of its particles. This review describes the background to PLRV and points towards these new developments.

Models of the predicted structure of a reconstituted trimer of PLRV coat protein. With permission from Terradot et al. (2001; Academic Press Inc.). (A) Surface (left) or section (right) views. Monomer units are in light green, dark green or blue. Epitope 5 (residues 8389) is shown in red, epitope 120 (residues 172-178) is shown in yellow. (B) Surfaces coloured according to the properties of the constituent amino acids: D, E-magenta; R, H, K-blue; A, V, L, I, P, M, F, W-orange; G, S, T, C, N, Q, Y-green. The acidic patch on the trimer surface is circled.

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