Interactions of the TGB1 Protein during Cell-to-Cell Movement of
            <i>Barley Stripe Mosaic Virus</i>

Lawrence, Diane M.; Jackson, Andrew O.

doi:10.1128/jvi.75.18.8712-8723.2001

Cited by 65 publications

(77 citation statements)

References 72 publications

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“…In the absence of TGB2 and TGB3, fluorescence was only associated with perinuclear ER and not plasma membranes (Lawrence and Jackson, 2001a). Similarly, punctate spots that colocalized with callose were seen in the walls of cells expressing Beet necrotic yellow vein virus (Group 1) TGB1 in the presence of TGB2 and TGB3 (Erhardt et al, 2000).…”

Section: Introductionmentioning

confidence: 85%

Two Plant–Viral Movement Proteins Traffic in the Endocytic Recycling Pathway

Haupt¹,

Cowan²,

Ziegler³

et al. 2005

The Plant Cell

195

157

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Many plant viruses exploit a conserved group of proteins known as the triple gene block (TGB) for cell-to-cell movement. Here, we investigated the interaction of two TGB proteins (TGB2 and TGB3) of Potato mop-top virus (PMTV), with components of the secretory and endocytic pathways when expressed as N-terminal fusions to green fluorescent protein or monomeric red fluorescent protein (mRFP). Our studies revealed that fluorophore-labeled TGB2 and TGB3 showed an early association with the endoplasmic reticulum (ER) and colocalized in motile granules that used the ER-actin network for intracellular movement. Both proteins increased the size exclusion limit of plasmodesmata, and TGB3 accumulated at plasmodesmata in the absence of TGB2. TGB3 contains a putative Tyr-based sorting motif, mutations in which abolished ER localization and plasmodesmatal targeting. Later in the expression cycle, both fusion proteins were incorporated into vesicular structures. TGB2 associated with these structures on its own, but TGB3 could not be incorporated into the vesicles in the absence of TGB2. Moreover, in addition to localization to the ER and motile granules, mRFP-TGB3 was incorporated into vesicles when expressed in PMTV-infected epidermal cells, indicating recruitment by virus-expressed TGB2. The TGB fusion protein-containing vesicles were labeled with FM4-64, a marker for plasma membrane internalization and components of the endocytic pathway. TGB2 also colocalized in vesicles with Ara7, a Rab5 ortholog that marks the early endosome. Protein interaction analysis revealed that recombinant TGB2 interacted with a tobacco protein belonging to the highly conserved RME-8 family of J-domain chaperones, shown to be essential for endocytic trafficking in Caenorhabditis elegans and Drosophila melanogaster. Collectively, the data indicate the involvement of the endocytic pathway in viral intracellular movement, the implications of which are discussed.

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Section: Introductionmentioning

confidence: 85%

Two Plant–Viral Movement Proteins Traffic in the Endocytic Recycling Pathway

Haupt¹,

Cowan²,

Ziegler³

et al. 2005

The Plant Cell

195

157

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“…Many, but not all, positive-strand RNA viruses recruit ER for the formation of the membrane-enveloped spherules to which replication complexes are sequestered (1). In addition, several plant virus MPs that function in a TMV-like, comovirus-like, or PVX-like manner were found in tight association with the ER (4,22,23,25,29,45). In most of these cases, the mechanistic significance of the MP-ER association is unclear.…”

Section: Discussionmentioning

confidence: 99%

Movement Protein of a Closterovirus Is a Type III Integral Transmembrane Protein Localized to the EndoplasmicReticulum

Peremyslov

Pan

Dolja

2004

J Virol

120

101

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Cell-to-cell movement of beet yellows closterovirus requires four structural proteins and a 6-kDa protein (p6) that is a conventional, nonstructural movement protein. Here we demonstrate that either virus infection or p6 overexpression results in association of p6 with the rough endoplasmic reticulum. The p6 protein possesses a single-span, transmembrane, N-terminal domain and a hydrophilic, C-terminal domain that is localized on the cytoplasmic face of the endoplasmic reticulum. In the infected cells, p6 forms a disulfide bridge via a cysteine residue located near the protein's N terminus. Mutagenic analyses indicated that each of the p6 domains, as well as protein dimerization, is essential for p6 function in virus movement.Transport of plant viruses within and between cells is an active process that requires the function of virus-coded movement proteins (MPs). By definition, MPs are specialized proteins that are essential for the translocation of viral genomes or virions, but they are not required for virus genome replication or encapsidation. Viral MPs belong to several distinct protein families, each of which seems to exhibit a unique functional profile (10, 26). Many virus genera possess not one but two or three MPs. In addition, cell-to-cell movement of some viruses requires proteins whose primary functions are in genome replication or encapsidation (8,9,21).Among several present models of virus movement, two have approached canonic status (10, 26). One is a Tobacco mosaic virus (TMV) model (4). The only TMV MP, the 30-kDa protein p30, is able to bind viral RNA and guide it through the plasmodesmata (13). Its additional activities include modification of plasmodesmatal gating properties and interactions with microtubules, actin microfilaments, endoplasmic reticulum (ER) (28,31,38), and a cell wall-specific host enzyme (12). However, the exact mechanistic contributions of these MP associations to intracellular movement are a matter of debate (6,17,41). Likewise, the transport mechanism of the RNA-MP complex through plasmodesmata largely remains a mystery. The leading model proposes that TMV-type MPs recruit a preexisting host machinery for intercellular trafficking (19,27). Interestingly, both rod-shaped RNA viruses related to TMV and several icosahedral RNA and single-stranded DNA viruses appear to follow this movement paradigm (16, 26).The second well-recognized model applies to several families of the icosahedral RNA viruses and pararetroviruses (35,42). The MPs of these viruses reorganize plasmodesmata by inducing formation of the tubules through which mature virions translocate from cell to cell. The MP and endomembrane secretion system appear to be sufficient for tubule formation, whereas intact cytoskeleton is required for proper positioning of the tubules relative to plasmodesmata (24).Mounting evidence indicates that the filamentous potexviruses do not fit in any of the abovementioned models. The 25-kDa MP (p25) of Potato virus X (PVX) possesses nucleoside triphosphatase and RNA helicase activitie...

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“…It is known however, that BSMV and the related hordeivirus PSLV TGB1 proteins are able to bind both single-stranded RNA and double-stranded RNA (dsRNA) with high affinity in vitro (10,23). In addition, the BSMV TGB2 and TGB3 proteins are required for cell-tocell movement (21,30) but their presence in the RNP has not been investigated, nor are their interactions with TGB1 understood. Thus, several intriguing questions regarding the possible binding interactions of TGB proteins and the nature of the viral RNAs associated with RNP complexes need to be answered to understand the movement mechanisms of BSMV and other hordeiviruses.…”

mentioning

confidence: 99%

Triple Gene Block Protein Interactions Involved in Movement of Barley Stripe Mosaic Virus

Lim

Bragg

Ganesan

et al. 2008

J Virol

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Barley stripe mosaic virus (BSMV) encodes three movement proteins in an overlapping triple gene block (TGB), but little is known about the physical interactions of these proteins. We have characterized a ribonucleoprotein (RNP) complex consisting of the TGB1 protein and plus-sense BSMV RNAs from infected barley plants and have identified TGB1 complexes in planta and in vitro. Homologous TGB1 binding was disrupted by site-specific mutations in each of the first two N-terminal helicase motifs but not by mutations in two C-terminal helicase motifs. The TGB2 and TGB3 proteins were not detected in the RNP, but affinity chromatography and yeast two-hybrid experiments demonstrated that TGB1 binds to TGB3 and that TGB2 and TGB3 form heterologous interactions. These interactions required the TGB2 glycine 40 and the TGB3 isoleucine 108 residues, and BSMV mutants containing these amino acid substitution were unable to move from cell to cell. Infectivity experiments indicated that TGB1 separated on a different genomic RNA from TGB2 and TGB3 could function in limited cell-to-cell movement but that the rates of movement depended on the levels of expression of the proteins and the contexts in which they are expressed. Moreover, elevated expression of the wild-type TGB3 protein interfered with cell-to-cell movement but movement was not affected by the similar expression of a TGB3 mutant that fails to interact with TGB2. These experiments suggest that BSMV movement requires physical interactions of TGB2 and TGB3 and that substantial deviation from the TGB protein ratios expressed by the wild-type virus compromises movement.For a virus to successfully invade a plant and cause disease, it must have the ability to move from cell to cell, establish localized infection foci, enter and exit the vascular system, and develop systemic infections. To accomplish these activities, plant viruses encode one or more movement proteins (MPs) that facilitate cell-to-cell movement and vascular transport. These proteins generally localize at plasmodesmata (PD) and increase the permeability of the PD sufficiently to permit the movement of macromolecules through the desmotubule (25, 38). Many MPs have RNA binding activities, and some act in concert with other virus-encoded proteins to facilitate virus movement and other activities such as RNA unwinding (18) or suppression of gene silencing (1, 24). Several general classes of viral MPs are known to exist, and these proteins provide tools for investigating a wide range of host-virus interactions and cellular functions (25,26).The most extensively investigated MPs are members of the 30K superfamily that are encoded by a large number of RNA and DNA viruses with different genome organizations (27). Over the past 15 years, studies of the processes carried out by proteins of the 30K movement family have provided great insight into the requirements for local and long-distance transport of Tobacco mosaic virus and a number of other viruses (4,15,25,38). The triple gene block (TGB) superfamily represents anoth...

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Interactions of the TGB1 Protein during Cell-to-Cell Movement of Barley Stripe Mosaic Virus

Cited by 65 publications

References 72 publications

Two Plant–Viral Movement Proteins Traffic in the Endocytic Recycling Pathway

Two Plant–Viral Movement Proteins Traffic in the Endocytic Recycling Pathway

Movement Protein of a Closterovirus Is a Type III Integral Transmembrane Protein Localized to the EndoplasmicReticulum

Triple Gene Block Protein Interactions Involved in Movement of Barley Stripe Mosaic Virus

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