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Importance of Hypericin-Bcl2 interactions for biological effects at subcellular levels. Photodiagnosis Photodyn Ther 2019; 28:38-52. [PMID: 31430575 DOI: 10.1016/j.pdpdt.2019.08.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/18/2019] [Accepted: 08/12/2019] [Indexed: 02/06/2023]
Abstract
Hypericin (Hyp) is a naturally occurring compound used as photosensitizer in photodynamic therapy and diagnosis. Recently, we have shown that Hyp presence alone, without illumination, resulted in substantial biological effects at several sub-cellular levels. Hyp induced changes in cellular ultrastructure, mitochondria function and metabolism, and distribution of Bcl2 proteins in malignant and non-malignant cells. The molecular mechanisms that underlie Hyp light-independent effects are still elusive. We have hypothesized that Bcl2-Hyp interactions might be one possible mechanism. We performed molecular docking studies to determine the Hyp-Bcl2 interaction profile. Based on the interaction profiles small Bcl2 peptide segments were selected for further study. We designed small peptides corresponding to Bcl2 BH3 and BH1 domains and tested the binding of Hyp and Bcl2 known inhibitor, ABT263, to the peptides in computer modeling and in vitro binding studies. We employed endogenous tryptophan and tyrosine in the BH3 and BH1 peptides, respectively, and their fluorescent properties to show interaction with Hyp and ABT263. Overall, our results indicate that Hyp can interact with Bcl2 protein at its BH3-BH1 hydrophobic groove, and this interaction may trigger changes in intracellular distribution of Bcl2 proteins. In addition, our computer modeling results suggest that Hyp also interacts with other anti-apoptotic members of Bcl2 family similar to the known BH3 mimetics. Our findings are novel and might contribute to understanding Hyp light-independent effects. In addition, they may substantiate the therapeutic use of Hyp as a BH3 mimetic molecule to enhance other cancer treatments.
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Navarro JA, Sanchez-Navarro JA, Pallas V. Key checkpoints in the movement of plant viruses through the host. Adv Virus Res 2019; 104:1-64. [PMID: 31439146 DOI: 10.1016/bs.aivir.2019.05.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Plant viruses cannot exploit any of the membrane fusion-based routes of entry described for animal viruses. In addition, one of the distinctive structures of plant cells, the cell wall, acts as the first barrier against the invasion of pathogens. To overcome the rigidity of the cell wall, plant viruses normally take advantage of the way of life of different biological vectors. Alternatively, the physical damage caused by environmental stresses can facilitate virus entry. Once inside the cell and taking advantage of the characteristic symplastic continuity of plant cells, viruses need to remodel and/or modify the restricted pore size of the plasmodesmata (channels that connect plant cells). In a successful interaction for the virus, it can reach the vascular tissue to systematically invade the plant. The connections between the different cell types in this path are not designed to allow the passage of molecules with the complexity of viruses. During this process, viruses face different cell barriers that must be overcome to reach the distal parts of the plant. In this review, we highlight the current knowledge about how plant RNA viruses enter plant cells, move between them to reach vascular cells and overcome the different physical and cellular barriers that the phloem imposes. Finally, we update the current research on cellular organelles as key regulator checkpoints in the long-distance movement of plant viruses.
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Affiliation(s)
- Jose A Navarro
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Jesus A Sanchez-Navarro
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Vicente Pallas
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain.
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Wu X, Liu J, Chai M, Wang J, Li D, Wang A, Cheng X. The Potato Virus X TGBp2 Protein Plays Dual Functional Roles in Viral Replication and Movement. J Virol 2019; 93:e01635-18. [PMID: 30541845 PMCID: PMC6384063 DOI: 10.1128/jvi.01635-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 12/03/2018] [Indexed: 01/27/2023] Open
Abstract
Plant 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 novel in vivo double-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.IMPORTANCE Many 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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Affiliation(s)
- Xiaoyun Wu
- College of Agriculture, Northeast Agriculture University, Harbin, China
| | - Jiahui Liu
- College of Agriculture, Northeast Agriculture University, Harbin, China
| | - Mengzhu Chai
- College of Agriculture, Northeast Agriculture University, Harbin, China
| | - Jinhui Wang
- College of Agriculture, Northeast Agriculture University, Harbin, China
| | - Dalong Li
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Northeast Region), Ministry of Agriculture, Northeast Agricultural University, Harbin, China
| | - Aiming Wang
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada
| | - Xiaofei Cheng
- College of Agriculture, Northeast Agriculture University, Harbin, China
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Chen I, Chen H, Huang Y, Huang H, Shenkwen L, Hsu Y, Tsai C. A thioredoxin NbTRXh2 from Nicotiana benthamiana negatively regulates the movement of Bamboo mosaic virus. MOLECULAR PLANT PATHOLOGY 2018; 19:405-417. [PMID: 28052479 PMCID: PMC6637981 DOI: 10.1111/mpp.12532] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 12/25/2016] [Accepted: 12/29/2016] [Indexed: 05/05/2023]
Abstract
An up-regulated gene derived from Bamboo mosaic virus (BaMV)-infected Nicotiana benthamiana plants was cloned and characterized in this study. BaMV is a single-stranded, positive-sense RNA virus. This gene product, designated as NbTRXh2, was matched with sequences of thioredoxin h proteins, a group of small proteins with a conserved active-site motif WCXPC conferring disulfide reductase activity. To examine how NbTRXh2 is involved in the infection cycle of BaMV, we used the virus-induced gene silencing technique to knock down NbTRXh2 expression in N. benthamiana and inoculated the plants with BaMV. We observed that, compared with control plants, BaMV coat protein accumulation increased in knockdown plants at 5 days post-inoculation (dpi). Furthermore, BaMV coat protein accumulation did not differ significantly between NbTRXh2-knockdown and control protoplasts at 24 hpi. The BaMV infection foci in NbTRXh2-knockdown plants were larger than those in control plants. In addition, BaMV coat protein accumulation decreased when NbTRXh2 was transiently expressed in plants. These results suggest that NbTRXh2 plays a role in restricting BaMV accumulation. Moreover, confocal microscopy results showed that NbTRXh2-OFP (NbTRXh2 fused with orange fluorescent protein) localized at the plasma membrane, similar to AtTRXh9, a homologue in Arabidopsis. The expression of the mutant that did not target the substrates failed to reduce BaMV accumulation. Co-immunoprecipitation experiments revealed that the viral movement protein TGBp2 could be the target of NbTRXh2. Overall, the functional role of NbTRXh2 in reducing the disulfide bonds of targeting factors, encoded either by the host or virus (TGBp2), is crucial in restricting BaMV movement.
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Affiliation(s)
- I‐Hsuan Chen
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
| | - Hui‐Ting Chen
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
| | - Ying‐Ping Huang
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
| | - Hui‐Chen Huang
- Biotechnology CenterNational Chung Hsing UniversityTaichung402Taiwan
| | - Lin‐Ling Shenkwen
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
| | - Yau‐Heiu Hsu
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
| | - Ching‐Hsiu Tsai
- Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichung402Taiwan
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Ho TL, Lee HC, Chou YL, Tseng YH, Huang WC, Wung CH, Lin NS, Hsu YH, Chang BY. The cysteine residues at the C-terminal tail of Bamboo mosaic virus triple gene block protein 2 are critical for efficient plasmodesmata localization of protein 1 in the same block. Virology 2017; 501:47-53. [PMID: 27863274 DOI: 10.1016/j.virol.2016.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 11/05/2016] [Indexed: 10/20/2022]
Abstract
The movement of some plant viruses are accomplished by three proteins encoded by a triple gene block (TGB). The second protein (TGBp2) in the block is a transmembrane protein. This study was aimed to unravel the mechanism underlying the relatively inefficient cell-to-cell movement of Bamboo mosaic virus (BaMV) caused by amino acid substitutions for the three Cys residues, Cys-109, Cys-112 and Cys-119, at the C-terminal tail of TGBp2. Results from confocal microscopy revealed that substitutions of the three Cys residues of TGBp2, especially Cys-109 and Cys-112, would reduce the efficiency of TGBp2- and TGBp3-dependent PD localization of TGBp1. Moreover, there is an additive effect of the substitutions on reducing the efficiency of PD localization of TGBp1. These results indicate that the Cys residues in the C-terminal tail region of TGBp2 participate in the TGBp2- and TGBp3-dependent PD localization of TGBp1, and thus influence the cell-to-cell movement capability of BaMV.
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Affiliation(s)
- Tsai-Ling Ho
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China
| | - Hsiang-Chi Lee
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China; Ph.D. Program in Microbial Genomics, National Chung-Hsing University and Academia Sinica, Taiwan, Republic of China
| | - Yuan-Lin Chou
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China
| | - Yang-Hao Tseng
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China
| | - Wei-Cheng Huang
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China
| | - Chiung-Hua Wung
- Biotechnology Center, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Na-Sheng Lin
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China; Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Yau-Heiu Hsu
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China
| | - Ban-Yang Chang
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China.
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Liou MR, Hu CC, Chou YL, Chang BY, Lin NS, Hsu YH. Viral elements and host cellular proteins in intercellular movement of Bamboo mosaic virus. Curr Opin Virol 2015; 12:99-108. [PMID: 25951346 DOI: 10.1016/j.coviro.2015.04.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 04/15/2015] [Accepted: 04/17/2015] [Indexed: 12/23/2022]
Abstract
As a member of the genus Potexvirus, Bamboo mosaic virus (BaMV) also belongs to the plant viruses that encode triple gene block proteins (TGBps) for intercellular movement within the host plants. Recent studies of the movement mechanisms of BaMV have revealed similarities and differences between BaMV and other potexviruses. This review focuses on the general aspects of viral and host elements involved in BaMV movement, the interactions among these elements, and the possible pathways for intra- and intercellular trafficking of BaMV. Major features of BaMV trafficking that have not been demonstrated in other potexviruses include: (i) the involvement of replicase, (ii) fine regulation by coat protein phosphorylation, (iii) the key roles played by TGBp3, (iv) the use of virions as the major transported form, and (v) the involvement of specific host factors, such as Ser/Thr kinase-like protein of Nicotiana benthamiana. We also highlight areas for future study that will provide a more comprehensive understanding of the detailed interactions among viral movement proteins and host factors, as well as the regulatory mechanisms of virus movement. Finally, a model based on the current knowledge is proposed to depict the diverse abilities of BaMV to utilize a wide range of mechanisms for efficient intercellular movement.
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Affiliation(s)
- Ming-Ru Liou
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan
| | - Chung-Chi Hu
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan
| | - Yuan-Lin Chou
- Institute of Biochemistry, National Chung Hsing University, Taichung 40227, Taiwan
| | - Ban-Yang Chang
- Institute of Biochemistry, National Chung Hsing University, Taichung 40227, Taiwan
| | - Na-Sheng Lin
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yau-Heiu Hsu
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan.
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Park MR, Jeong RD, Kim KH. Understanding the intracellular trafficking and intercellular transport of potexviruses in their host plants. FRONTIERS IN PLANT SCIENCE 2014; 5:60. [PMID: 24672528 PMCID: PMC3957223 DOI: 10.3389/fpls.2014.00060] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 02/06/2014] [Indexed: 05/22/2023]
Abstract
The movement of potexviruses through the cytoplasm to plasmodesmata (PD) and through PD to adjacent cells depends on the viral and host cellular proteins. Potexviruses encode three movement proteins [referred to as the triple gene block (TGB1-3)]. TGB1 protein moves cell-to-cell through PD and requires TGB2 and TGB3, which are endoplasmic reticulum (ER)-located proteins. TGB3 protein directs the movement of the ER-derived vesicles induced by TGB2 protein from the perinuclear ER to the cortical ER. TGB2 protein physically interacts with TGB3 protein in a membrane-associated form and also interacts with either coat protein (CP) or TGB1 protein at the ER network. Recent studies indicate that potexvirus movement involves the interaction between TGB proteins and CP with host proteins including membrane rafts. A group of host cellular membrane raft proteins, remorins, can serve as a counteracting membrane platform for viral ribonucleoprotein (RNP) docking and can thereby inhibit viral movement. The CP, which is a component of the RNP movement complex, is also critical for viral cell-to-cell movement through the PD. Interactions between TGB1 protein and/or the CP subunit with the 5'-terminus of genomic RNA [viral RNA (vRNA)] form RNP movement complexes and direct the movement of vRNAs through the PD. Recent studies show that tobacco proteins such as NbMPB2C or NbDnaJ-like proteins interact with the stem-loop 1 RNA located at the 5'-terminus of Potato virus X vRNA and regulate intracellular as well as intercellular movement. Although several host proteins that interact with vRNAs or viral proteins and that are crucial for vRNA transport have been screened and characterized, additional host proteins and details of viral movement remain to be characterized. In this review, we describe recent progress in understanding potexvirus movement within and between cells and how such movement is affected by interactions between vRNA/proteins and host proteins.
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Affiliation(s)
- Mi-Ri Park
- Department of Agricultural Biotechnology, Seoul National UniversitySeoul, South Korea
- Plant Genomics and Breeding Institute, Seoul National UniversitySeoul, South Korea
- Research Institute for Agriculture and Life Sciences, Seoul National UniversitySeoul, South Korea
| | - Rae-Dong Jeong
- Advanced Radiation Technology Institute, Korea Atomic Energy Research InstituteJeongeup, South Korea
| | - Kook-Hyung Kim
- Department of Agricultural Biotechnology, Seoul National UniversitySeoul, South Korea
- Plant Genomics and Breeding Institute, Seoul National UniversitySeoul, South Korea
- Research Institute for Agriculture and Life Sciences, Seoul National UniversitySeoul, South Korea
- *Correspondence: Kook-Hyung Kim, Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, South Korea e-mail:
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Park MR, Seo JK, Kim KH. Viral and nonviral elements in potexvirus replication and movement and in antiviral responses. Adv Virus Res 2013; 87:75-112. [PMID: 23809921 DOI: 10.1016/b978-0-12-407698-3.00003-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In Potato virus X, a member of the genus Potexvirus, special sequences and structures at the 5' and 3' ends of the nontranslated region function as cis-acting elements for viral replication. These elements greatly affect interactions between viral RNAs and those between viral RNAs and host factors. The potexvirus genome encodes five open-reading frames. Viral replicase, which is required for the synthesis of viral RNA, binds viral RNA elements and host factors to form a viral replication complex at the host cellular membrane. The coat protein (CP) and three viral movement proteins (TGB1, TGB2, and TGB3) have critical roles in mediating cell-to-cell viral movement through plasmodesmata by virion formation or by nonvirion ribonucleoprotein (RNP) complex formation with viral movement proteins (TGBs). The RNP complex, like TGB1-CP-viral RNA, is associated with viral replicase and used for immediate reinitiation of viral replication in newly invaded cells. Higher plants have defense mechanisms against potexviruses such as Rx-mediated resistance and RNA silencing. The CP acts as an avirulence effector for plant defense mechanisms, while TGB1 functions as a viral suppressor of RNA silencing, which is the mechanism of innate immune resistance. Here, we describe recent findings concerning the involvement of viral and host factors in potexvirus replication and in antiviral responses to potexvirus infection.
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Affiliation(s)
- Mi-Ri Park
- Department of Agricultural Biotechnology, Plant Genomics and Breeding Institute, Seoul National University, Seoul, Republic of Korea
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9
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Tilsner J, Linnik O, Louveaux M, Roberts IM, Chapman SN, Oparka KJ. Replication and trafficking of a plant virus are coupled at the entrances of plasmodesmata. J Cell Biol 2013; 201:981-95. [PMID: 23798728 PMCID: PMC3691464 DOI: 10.1083/jcb.201304003] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 05/16/2013] [Indexed: 02/04/2023] Open
Abstract
Plant viruses use movement proteins (MPs) to modify intercellular pores called plasmodesmata (PD) to cross the plant cell wall. Many viruses encode a conserved set of three MPs, known as the triple gene block (TGB), typified by Potato virus X (PVX). In this paper, using live-cell imaging of viral RNA (vRNA) and virus-encoded proteins, we show that the TGB proteins have distinct functions during movement. TGB2 and TGB3 established endoplasmic reticulum-derived membranous caps at PD orifices. These caps harbored the PVX replicase and nonencapsidated vRNA and represented PD-anchored viral replication sites. TGB1 mediated insertion of the viral coat protein into PD, probably by its interaction with the 5' end of nascent virions, and was recruited to PD by the TGB2/3 complex. We propose a new model of plant virus movement, which we term coreplicational insertion, in which MPs function to compartmentalize replication complexes at PD for localized RNA synthesis and directional trafficking of the virus between cells.
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Affiliation(s)
- Jens Tilsner
- Biomedical Sciences Research Complex, University of St Andrews, Fife KY16 9ST, Scotland, UK.
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Chou YL, Hung YJ, Tseng YH, Hsu HT, Yang JY, Wung CH, Lin NS, Meng M, Hsu YH, Chang BY. The stable association of virion with the triple-gene-block protein 3-based complex of Bamboo mosaic virus. PLoS Pathog 2013; 9:e1003405. [PMID: 23754943 PMCID: PMC3675025 DOI: 10.1371/journal.ppat.1003405] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 04/22/2013] [Indexed: 12/03/2022] Open
Abstract
The triple-gene-block protein 3 (TGBp3) of Bamboo mosaic virus (BaMV) is an integral endoplasmic reticulum (ER) membrane protein which is assumed to form a membrane complex to deliver the virus intracellularly. However, the virus entity that is delivered to plasmodesmata (PD) and its association with TGBp3-based complexes are not known. Results from chemical extraction and partial proteolysis of TGBp3 in membrane vesicles revealed that TGBp3 has a right-side-out membrane topology; i.e., TGBp3 has its C-terminal tail exposed to the outer surface of ER. Analyses of the TGBp3-specific immunoprecipitate of Sarkosyl-extracted TGBp3-based complex revealed that TGBp1, TGBp2, TGBp3, capsid protein (CP), replicase and viral RNA are potential constituents of virus movement complex. Substantial co-fractionation of TGBp2, TGBp3 and CP, but not TGBp1, in the early eluted gel filtration fractions in which virions were detected after TGBp3-specific immunoprecipitation suggested that the TGBp2- and TGBp3-based complex is able to stably associate with the virion. This notion was confirmed by immunogold-labeling transmission electron microscopy (TEM) of the purified virions. In addition, mutational and confocal microscopy analyses revealed that TGBp3 plays a key role in virus cell-to-cell movement by enhancing the TGBp2- and TGBp3-dependent PD localization of TGBp1. Taken together, our results suggested that the cell-to-cell movement of potexvirus requires stable association of the virion cargo with the TGBp2- and TGBp3-based membrane complex and recruitment of TGBp1 to the PD by this complex.
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Affiliation(s)
- Yuan-Lin Chou
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Yi-Jing Hung
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Yang-Hao Tseng
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Hsiu-Ting Hsu
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Jun-Yi Yang
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Chiung-Hua Wung
- Biotechnology Center, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Na-Sheng Lin
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Menghsiao Meng
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Yau-Heiu Hsu
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Ban-Yang Chang
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China
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Cho SY, Cho WK, Choi HS, Kim KH. Cis-acting element (SL1) of Potato virus X controls viral movement by interacting with the NbMPB2Cb and viral proteins. Virology 2012; 427:166-76. [PMID: 22405626 DOI: 10.1016/j.virol.2012.02.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 01/09/2012] [Accepted: 02/04/2012] [Indexed: 01/21/2023]
Abstract
A number of candidate tobacco proteins that bind to cis-acting elements (SL1 RNAs) of Potato virus X (PVX) have been identified in previous studies. We further characterized TMV-MP30 binding protein 2C (MPB2C) homologous protein. We isolated NbMPB2Cb from Nicotiana benthamiana and confirmed the interaction of NbMPB2Cb with SL1 RNAs in vitro. The mRNA level of NbMPB2Cb was increased upon infection by PVX and Tobacco mosaic virus. The movement of PVX was reduced by overexpression of NbMPB2Cb and increased by silenced of NbMPB2Cb. In contrast, PVX RNA accumulation was not significantly altered in protoplasts. Protein-protein interaction assays showed that NbMPB2Cb interacts with PVX movement-associated proteins. PVX infection altered the subcellular localization of NbMPB2Cb from microtubules to endoplasmic reticulum. These data suggest that the NbMPB2Cb negatively affects PVX movement by interacting with SL1 RNAs and movement-associated proteins of PVX and by re-localizing in response to PVX infection.
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Affiliation(s)
- Sang-Yun Cho
- Department of Agricultural Biotechnology and Plant Genomics and Breeding Institute, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea
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Schoelz JE, Harries PA, Nelson RS. Intracellular transport of plant viruses: finding the door out of the cell. MOLECULAR PLANT 2011; 4:813-31. [PMID: 21896501 PMCID: PMC3183398 DOI: 10.1093/mp/ssr070] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 07/18/2011] [Indexed: 05/03/2023]
Abstract
Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein (MP), a protein dedicated to enlarging the pore size of plasmodesmata (PD) and actively transporting the viral nucleic acid into the adjacent cell. As our knowledge of intercellular transport has increased, it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD. Just as viruses are too large to fit through an unmodified plasmodesma, they are also too large to be freely diffused through the cytoplasm of the cell. Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP, including viral proteins originally associated with replication or gene expression. In this review, we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD, in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.
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Affiliation(s)
- James E. Schoelz
- Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Phillip A. Harries
- Department of Biology, Pittsburg State University, Pittsburg, KS 66762, USA
| | - Richard S. Nelson
- Plant Biology Division, The Samuel Roberts Noble Foundation, Inc., Ardmore, OK 73401, USA
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Wright KM, Cowan GH, Lukhovitskaya NI, Tilsner J, Roberts AG, Savenkov EI, Torrance L. The N-terminal domain of PMTV TGB1 movement protein is required for nucleolar localization, microtubule association, and long-distance movement. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:1486-97. [PMID: 20923354 DOI: 10.1094/mpmi-05-10-0105] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The triple-gene-block (TGB)1 protein of Potato mop-top virus (PMTV) was fused to fluorescent proteins and expressed in epidermal cells of Nicotiana benthamiana under the control of the 35S promoter. TGB1 fluorescence was observed in the cytoplasm, nucleus, and nucleolus and occasionally associated with microtubules. When expressed from a modified virus (PMTV.YFP-TGB1) which formed local lesions but was not competent for systemic movement, yellow fluorescent protein (YFP)-TGB1 labeled plasmodesmata in cells at the leading edge of the lesion and plasmodesmata, microtubules, nuclei, and nucleoli in cells immediately behind the leading edge. Deletion of 84 amino acids from the N-terminus of unlabeled TGB1 within the PMTV genome abolished movement of viral RNA to noninoculated leaves. When the same deletion was introduced into PMTV.YFP-TGB1, labeling of microtubules and nucleoli was abolished. The N-terminal 84 amino acids of TGB1 were fused to green fluorescent protein (GFP) and expressed in epidermal cells where GFP localized strongly to the nucleolus (not seen with unfused GFP), indicating that these amino acids contain a nucleolar localization signal; the fusion protein did not label microtubules. This is the first report of nucleolar and microtubule association of a TGB movement protein. The results suggest that PMTV TGB1 requires interaction with nuclear components and, possibly, microtubules for long-distance movement of viral RNA.
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Affiliation(s)
- Kathryn M Wright
- Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
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Verchot-Lubicz J, Torrance L, Solovyev AG, Morozov SY, Jackson AO, Gilmer D. Varied movement strategies employed by triple gene block-encoding viruses. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:1231-47. [PMID: 20831404 DOI: 10.1094/mpmi-04-10-0086] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
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.
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Affiliation(s)
- Jeanmarie Verchot-Lubicz
- Oklahoma State University, Department of Entomology and Plant Pathology, Stillwater, OK 74078, USA.
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