Potato leafroll virus: a classic pathogen shows some new tricks

Abstract

SUMMARY 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. 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.

The C Terminus of the Polerovirus P5 Readthrough Domain Limits Virus Infection to the Phloem

“…The prevailing hypotheses to explain the phloem limitation of poleroviruses such as PLRV are that the virus is unable to suppress plant defense mechanisms outside of the phloem or that the viruses lack a movement protein that can function in nonvascular tissues (36). Our current study has demonstrated an alternative explanation: the virus encodes a protein, P5, which confines the virus to phloem tissues.…”

“…Although luteovirids encode at least two movement proteins and move locally and long distance in vascular tissues, they are unable to move between nonvascular cells or between nonvascular and vascular tissues (36). This phloem limitation is generally attributed to a lack of or an inability of luteovirid movement proteins to function in nonvascular tissues or because the virus cannot suppress a silencing-based plant defense mechanism outside of phloem tissues (5,36).…”

Simple and Rapid Detection of Potato leafroll virus by Reverse Transcription Loop-mediated Isothermal Amplification

“…The PLRV forms icosahedral particles containing a 5.8 kb single-stranded (+) sense RNA that consists of eight open reading frames (ORFs) (Harrison, 1984;Taliansky et al, 2003). As PLRV is a member of the genus Polerovirus (family Luteoviridae), unlike the majority of plant viruses PLRV is restricted to the phloem-associated tissues (Gray and Gildow, 2003;Nurkiyanova et al, 2000;Taliansky et al, 2003). It is transmitted by a limited number of aphid species in a non-propagative circulative manner from plant to plant (Gray and Gildow, 2003;Harrison, 1985;Taliansky et al, 2003).…”

Visualization of Host-Polerovirus Interaction Topologies Using Protein Interaction Reporter Technology

“…6 to 8). Alternatively, these data may represent interactions with virions at different stages of assembly that copurified with intact virions (59,68) or even multimeric forms of the structural proteins (58) that could act in trans to regulate PLRV infection. It is known that viral proteins can be a part of many different host protein complexes that are dynamically regulated throughout the course of an infection (73,74).…”

“…Only one model ( Fig. 8C and D) predicted the N-terminal sequence of a CP monomer to be surface exposed, a model that is supported by epitope mapping (59) and hypothesized to occur during virus disassembly (68). Visualization of the PsbQ2-CP dimer interface using this CP dimer model predicts two general interaction topologies, one where PsbQ2 interacts with the internal CP arginine-rich domain (Fig.…”