scholarly journals Varied Movement Strategies Employed by Triple Gene Block–Encoding Viruses

2010 ◽  
Vol 23 (10) ◽  
pp. 1231-1247 ◽  
Author(s):  
Jeanmarie Verchot-Lubicz ◽  
Lesley Torrance ◽  
Andrey G. Solovyev ◽  
Sergey Yu Morozov ◽  
Andrew O. Jackson ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Rna Virus ◽  
Triple Gene Block ◽  
Cell Movement ◽  
Future Research ◽  
Subcellular Targeting ◽  
Long Distance ◽  
Movement Proteins ◽  
Gene Block ◽  
Long Distance Movement

Several RNA virus genera belonging to the Virgaviridae and Flexiviridae families encode proteins organized in a triple gene block (TGB) that facilitate cell-to-cell and long-distance movement. The TGB proteins have been traditionally classified as hordei-like or potex-like based on phylogenetic comparisons and differences in movement mechanisms of the Hordeivirus and Potexvirus spp. However, accumulating data from other model viruses suggests that a revised framework is needed to accommodate the profound differences in protein interactions occurring during infection and ancillary capsid protein requirements for movement. The goal of this article is to highlight common features of the TGB proteins and salient differences in movement properties exhibited by individual viruses encoding these proteins. We discuss common and divergent aspects of the TGB transport machinery, describe putative nucleoprotein movement complexes, highlight recent data on TGB protein interactions and topological properties, and review membrane associations occurring during subcellular targeting and cell-to-cell movement. We conclude that the existing models cannot be used to explain all TGB viruses, and we propose provisional Potexvirus, Hordeivirus, and Pomovirus models. We also suggest areas that might profit from future research on viruses harboring this intriguing arrangement of movement proteins.

scholarly journals P42 Movement Protein of Beet necrotic yellow vein virus Is Targeted by the Movement Proteins P13 and P15 to Punctate Bodies Associated with Plasmodesmata

2000 ◽  
Vol 13 (5) ◽  
pp. 520-528 ◽  
Author(s):  
M. Erhardt ◽  
M. Morant ◽  
C. Ritzenthaler ◽  
C. Stussi-Garaud ◽  
H. Guilley ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fluorescent Protein ◽  
Triple Gene Block ◽  
Point Mutations ◽  
Cell Movement ◽  
Leading Edge ◽  
Yellow Vein ◽  
Body Formation ◽  
Movement Proteins ◽  
Gene Block

Cell-to-cell movement of Beet necrotic yellow vein virus (BNYVV) is driven by a set of three movement proteins—P42, P13, and P15—organized into a triple gene block (TGB) on viral RNA 2. The first TGB protein, P42, has been fused to the green fluorescent protein (GFP) and fusion proteins between P42 and GFP were expressed from a BNYVV RNA 3-based replicon during virus infection. GFP-P42, in which the GFP was fused to the P42 N terminus, could drive viral cell-to-cell movement when the copy of the P42 gene on RNA 2 was disabled but the C-terminal fusion P42-GFP could not. Confocal microscopy of epidermal cells of Chenopodium quinoa near the leading edge of the infection revealed that GFP-P42 localized to punctate bodies apposed to the cell wall whereas free GFP, expressed from the replicon, was distributed uniformly throughout the cytoplasm. The punctate bodies sometimes appeared to traverse the cell wall or to form pairs of disconnected bodies on each side. The punctate bodies co-localized with callose, indicating that they are associated with plasmodesmata-rich regions such as pit fields. Point mutations in P42 that inhibited its ability to drive cell-to-cell movement also inhibited GFP-P42 punctate body formation. GFP-P42 punctate body formation was dependent on expression of P13 and P15 during the infection, indicating that these proteins act together or sequentially to localize P42 to the plasmodesmata.

scholarly journals Mutation of a chloroplast-targeting signal in Alternanthera mosaic virus TGB3 impairs cell-to-cell movement and eliminates long-distance virus movement

2010 ◽  
Vol 91 (8) ◽  
pp. 2102-2115 ◽  
Author(s):  
Hyoun-Sub Lim ◽  
Anna Maria Vaira ◽  
Hanhong Bae ◽  
Jennifer N. Bragg ◽  
Steven E. Ruzin ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Critical Role ◽  
Triple Gene Block ◽  
Cell Movement ◽  
Potato Virus X ◽  
Start Codon ◽  
Long Distance ◽  
Mesophyll Cells ◽  
Chloroplast Targeting ◽  
Gene Block

Cell-to-cell movement of potexviruses requires coordinated action of the coat protein and triple gene block (TGB) proteins. The structural properties of Alternanthera mosaic virus (AltMV) TGB3 were examined by methods differentiating between signal peptides and transmembrane domains, and its subcellular localization was studied by Agrobacterium-mediated transient expression and confocal microscopy. Unlike potato virus X (PVX) TGB3, AltMV TGB3 was not associated with the endoplasmic reticulum, and accumulated preferentially in mesophyll cells. Deletion and site-specific mutagenesis revealed an internal signal VL(17,18) of TGB3 essential for chloroplast localization, and either deletion of the TGB3 start codon or alteration of the chloroplast-localization signal limited cell-to-cell movement to the epidermis, yielding a virus that was unable to move into the mesophyll layer. Overexpression of AltMV TGB3 from either AltMV or PVX infectious clones resulted in veinal necrosis and vesiculation at the chloroplast membrane, a cytopathology not observed in wild-type infections. The distinctive mesophyll and chloroplast localization of AltMV TGB3 highlights the critical role played by mesophyll targeting in virus long-distance movement within plants.

scholarly journals Defective Movement of Viruses in the Family Bromoviridae Is Differentially Complemented in Nicotiana benthamiana Expressing Tobamovirus or Dianthovirus Movement Proteins

1998 ◽  
Vol 88 (7) ◽  
pp. 666-672 ◽  
Author(s):  
A. L. N. Rao ◽  
Bret Cooper ◽  
Carl M. Deom
Keyword(s):  
Nicotiana Benthamiana ◽  
Cell Movement ◽  
Red Clover ◽  
Amino Acid Identity ◽  
Progeny Virus ◽  
Long Distance ◽  
Movement Proteins ◽  
Brome Mosaic Bromovirus ◽  
Chlorotic Mottle ◽  
Long Distance Movement

Taxonomically distinct tobacco mosaic tobamovirus (TMV), red clover necrotic mosaic dianthovirus (RCNMV), cucumber mosaic cucumovirus (CMV), brome mosaic bromovirus (BMV), and cowpea chlorotic mottle bromovirus (CCMV) exhibit differences in their host range. Each of these viruses encodes a functionally similar nonstructural movement protein (MP) that is essential for cell-to-cell movement of a progeny virus. Despite the lack of significant amino acid identity among the MPs of CMV, TMV, and RCNMV, movement-defective CMV (CMVFnyΔMP-ΔKPN) was able to move locally and systemically in transgenic Nicotiana benthamiana expressing either TMV MP (NB-TMV-MP(+)) or RCNMV MP (NB-RCNMV-MP(+)). These observations contrast with those of previous studies in which transgenic N. tabacum cv. Xanthi plants expressing TMV MP supported only the cell-to-cell movement of CMVFnyΔMP-ΔKPN. To verify whether similar complementation could be observed for movement-defective bromoviruses, NB-TMV-MP(+) and NB-RCNMV-MP(+) plants were inoculated independently with movement-defective variants of BMV (B3ΔMP) and CCMV (CC3ΔMP). Neither NB-TMV-MP(+) nor NB-RCNMV-MP(+) was able to rescue the defective cell-to-cell and long-distance movement of B3ΔMP. In contrast, NB-RCNMV-MP(+) complemented the cell-to-cell, but not the long-distance, movement of CC3ΔMP. Taken together, these studies suggest that virus movement is a complex process and that, in some cases, the host species plays a major role in determining the long-distance movement function of a virus.

scholarly journals ICTV Virus Taxonomy Profile: Alphaflexiviridae

2020 ◽  
Vol 101 (7) ◽  
pp. 699-700 ◽  
Author(s):  
Jan F. Kreuze ◽  
Anna Maria Vaira ◽  
Wulf Menzel ◽  
Thierry Candresse ◽  
Sergey K. Zavriev ◽  
...  
Keyword(s):  
Triple Gene Block ◽  
International Committee ◽  
Replication Proteins ◽  
Virus Taxonomy ◽  
Long Distance ◽  
Gene Block ◽  
The Family ◽  
Single Exception ◽  
Distinct Lineage ◽  
Long Distance Movement

The family Alphaflexiviridae includes viruses with flexuous filamentous virions that are 470–800 nm in length and 12–13 nm in diameter. Alphaflexiviruses have a single-stranded, positive-sense RNA genome of 5.5–9 kb. They infect plants and plant-infecting fungi. They share a distinct lineage of alphavirus-like replication proteins that is unusual in lacking any recognized protease domain. With a single exception, cell-to-cell and long-distance movement is facilitated by triple gene block proteins in plant-infecting genera. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Alphaflexiviridae, which is available at www.ictv.global/report/alphaflexiviridae.

scholarly journals Trans-Complementation of Long-Distance Movement of White clover mosaic virus Triple Gene Block (TGB) Mutants: Phloem-Associated Movement of TGBp1

Virology ◽  
2001 ◽  
Vol 288 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Tony J. Lough ◽  
Sarah J. Emerson ◽  
William J. Lucas ◽  
Richard L.S. Forster
Keyword(s):  
Mosaic Virus ◽  
White Clover ◽  
Triple Gene Block ◽  
Long Distance ◽  
Gene Block ◽  
Long Distance Movement ◽  
White Clover Mosaic Virus

scholarly journals Subcellular Localization of the Barley Stripe Mosaic Virus Triple Gene Block Proteins

2009 ◽  
Vol 83 (18) ◽  
pp. 9432-9448 ◽  
Author(s):  
Hyoun-Sub Lim ◽  
Jennifer N. Bragg ◽  
Uma Ganesan ◽  
Steven Ruzin ◽  
Denise Schichnes ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Mosaic Virus ◽  
Protein Interactions ◽  
Close Association ◽  
Triple Gene Block ◽  
Single Amino Acid ◽  
Barley Stripe Mosaic Virus ◽  
Subcellular Targeting ◽  
Site Specific ◽  
Gene Block

ABSTRACT Barley stripe mosaic virus (BSMV) spreads from cell to cell through the coordinated actions of three triple gene block (TGB) proteins (TGB1, TGB2, and TGB3) arranged in overlapping open reading frames (ORFs). Our previous studies (D. M. Lawrence and A. O. Jackson, J. Virol. 75:8712-8723, 2001; D. M. Lawrence and A. O. Jackson, Mol. Plant Pathol. 2:65-75, 2001) have shown that each of these proteins is required for cell-to-cell movement in monocot and dicot hosts. We recently found (H.-S. Lim, J. N. Bragg, U. Ganesan, D. M. Lawrence, J. Yu, M. Isogai, J. Hammond, and A. O. Jackson, J. Virol. 82:4991-5006, 2008) that TGB1 engages in homologous interactions leading to the formation of a ribonucleoprotein complex containing viral genomic and messenger RNAs, and we have also demonstrated that TGB3 functions in heterologous interactions with TGB1 and TGB2. We have now used Agrobacterium tumefaciens-mediated protein expression in Nicotiana benthamiana leaf cells and site-specific mutagenesis to determine how TGB protein interactions influence their subcellular localization and virus spread. Confocal microscopy revealed that the TGB3 protein localizes at the cell wall (CW) in close association with plasmodesmata and that the deletion or mutagenesis of a single amino acid at the immediate C terminus can affect CW targeting. TGB3 also directed the localization of TGB2 from the endoplasmic reticulum to the CW, and this targeting was shown to be dependent on interactions between the TGB2 and TGB3 proteins. The optimal localization of the TGB1 protein at the CW also required TGB2 and TGB3 interactions, but in this context, site-specific TGB1 helicase motif mutants varied in their localization patterns. The results suggest that the ability of TGB1 to engage in homologous binding interactions is not essential for targeting to the CW. However, the relative expression levels of TGB2 and TGB3 influenced the cytosolic and CW distributions of TGB1 and TGB2. Moreover, in both cases, localization at the CW was optimal at the 10:1 TGB2-to-TGB3 ratios occurring in virus infections, and mutations reducing CW localization had corresponding effects on BSMV movement phenotypes. These data support a model whereby TGB protein interactions function in the subcellular targeting of movement protein complexes and the ability of BSMV to move from cell to cell.

scholarly journals Cell-to-Cell Movement of Beet Necrotic Yellow Vein Virus: I. Heterologous Complementation Experiments Provide Evidence for Specific Interactions Among the Triple Gene Block Proteins

1998 ◽  
Vol 11 (7) ◽  
pp. 618-625 ◽  
Author(s):  
Emmanuelle Lauber ◽  
Claudine Bleykasten-Grosshans ◽  
M. Erhardt ◽  
S. Bouzoubaa ◽  
G. Jonard ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Triple Gene Block ◽  
Chenopodium Quinoa ◽  
Alfalfa Mosaic Virus ◽  
Cell Movement ◽  
Yellow Vein ◽  
Specific Interactions ◽  
In Planta ◽  
Movement Proteins ◽  
Gene Block

Cell-to-cell movement of beet necrotic yellow vein virus (BNYVV) requires three proteins encoded by a triple gene block (TGB) on viral RNA 2. A BNYVV RNA 3-derived replicon was used to express movement proteins of other viruses and the ability of these proteins to functionally substitute for the BNYVV TGB proteins was tested by coinoculation of TGB-defective BNYVV with the various replicons to Chenopodium quinoa. Trans-heterocomplementation was successful with the movement protein (P30) of tobacco mosaic virus but not with the tubule-forming movement proteins of alfalfa mosaic virus and grapevine fanleaf virus. Trans-complementation of BNYVV movement was also observed when all three TGB proteins of the distantly related peanut clump virus were supplied together but not when they were substituted for their BNYVV counterparts one by one. When P30 was used to drive BNYVV movement in trans, accumulation of the first TGB protein of BNYVV was adversely affected by null mutations in the second and third TGB proteins. Taken together, these results suggest that highly specific interactions among cognate TGB proteins are important for their function and/or stability in planta.

scholarly journals Molecular biology of potexviruses: recent advances

2007 ◽  
Vol 88 (6) ◽  
pp. 1643-1655 ◽  
Author(s):  
Jeanmarie Verchot-Lubicz ◽  
Chang-Ming Ye ◽  
Devinka Bamunusinghe
Keyword(s):  
Gene Silencing ◽  
Rna Synthesis ◽  
Triple Gene Block ◽  
Potato Virus X ◽  
Future Research ◽  
Virus Movement ◽  
Suppressor Activity ◽  
Gene Block ◽  
Recent Advances

Recent advances in potexvirus research have produced new models describing virus replication, cell-to-cell movement, encapsidation, R gene-mediated resistance and gene silencing. Interactions between distant RNA elements are a central theme in potexvirus replication. The 5′ non-translated region (NTR) regulates genomic and subgenomic RNA synthesis and encapsidation, as well as virus plasmodesmal transport. The 3′ NTR regulates both plus- and minus-strand RNA synthesis. How the triple gene-block proteins interact for virus movement is still elusive. As the potato virus X (PVX) TGBp1 protein gates plasmodesmata, regulates virus translation and is a suppressor of RNA silencing, further research is needed to determine how these properties contribute to propelling virus through the plasmodesmata. Specifically, TGBp1 suppressor activity is required for virus movement, but how the silencing machinery relates to plasmodesmata is not known. The TGBp2 and TGBp3 proteins are endoplasmic reticulum (ER)-associated proteins required for virus movement. TGBp2 associates with ER-derived vesicles that traffic along the actin network. Future research will determine whether the virus-induced vesicles are cytopathic structures regulating events along the ER or are vehicles carrying virus to the plasmodesmata for transfer into neighbouring cells. Efforts to assemble virions in vitro identified a single-tailed particle (STP) comprising RNA, coat protein (CP) and TGBp1. It has been proposed that TGBp1 aids in transport of virions or STP between cells and ensures translation of RNA in the receiving cells. PVX is also a tool for studying Avr–R gene interactions and gene silencing in plants. The PVX CP is the elicitor for the Rx gene. Recent reports of the PVX CP reveal how CP interacts with the Rx gene product.

scholarly journals The Potato Virus X TGBp2 Protein Plays Dual Functional Roles in Viral Replication and Movement

2018 ◽  
Vol 93 (5) ◽  
Author(s):  
Xiaoyun Wu ◽  
Jiahui Liu ◽  
Mengzhu Chai ◽  
Jinhui Wang ◽  
Dalong Li ◽  
...  
Keyword(s):  
Triple Gene Block ◽  
Potato Virus X ◽  
Plant Viruses ◽  
Open Reading Frames ◽  
Movement Proteins ◽  
Gene Block ◽  
Functional Roles ◽  
Viral Rdrp ◽  
Dual Functional ◽  
Intercellular Movement

ABSTRACTPlant viruses usually encode one or more movement proteins (MP) to accomplish their intercellular movement. A group of positive-strand RNA plant viruses requires three viral proteins (TGBp1, TGBp2, and TGBp3) that are encoded by an evolutionarily conserved genetic module of three partially overlapping open reading frames (ORFs), termed the triple gene block (TGB). However, how these three viral movement proteins function cooperatively in viral intercellular movement is still elusive. Using a novelin vivodouble-stranded RNA (dsRNA) labeling system, we showed that the dsRNAs generated by potato virus X (PVX) RNA-dependent RNA polymerase (RdRp) are colocalized with viral RdRp, which are further tightly covered by “chain mail”-like TGBp2 aggregates and localizes alongside TGBp3 aggregates. We also discovered that TGBp2 interacts with the C-terminal domain of PVX RdRp, and this interaction is required for the localization of TGBp3 and itself to the RdRp/dsRNA bodies. Moreover, we reveal that the central and C-terminal hydrophilic domains of TGBp2 are required to interact with viral RdRp. Finally, we demonstrate that knockout of the entire TGBp2 or the domain involved in interacting with viral RdRp attenuates both PVX replication and movement. Collectively, these findings suggest that TGBp2 plays dual functional roles in PVX replication and intercellular movement.IMPORTANCEMany plant viruses contain three partially overlapping open reading frames (ORFs), termed the triple gene block (TGB), for intercellular movement. However, how the corresponding three proteins coordinate their functions remains obscure. In the present study, we provided multiple lines of evidence supporting the notion that PVX TGBp2 functions as the molecular adaptor bridging the interaction between the RdRp/dsRNA body and TGBp3 by forming “chain mail”-like structures in the RdRp/dsRNA body, which can also enhance viral replication. Taken together, our results provide new insights into the replication and movement of PVX and possibly also other TGB-containing plant viruses.

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