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Thomas Hohn - One of the best experts on this subject based on the ideXlab platform.

  • plant pararetroViruses interactions of Cauliflower Mosaic Virus with plants and insects
    Current Opinion in Virology, 2013
    Co-Authors: Thomas Hohn
    Abstract:

    Virion associated protein (VAP) binds to the icosahedral capsid of Cauliflower Mosaic Virus (CaMV) - a plant pararetroVirus. The interactive coiled-coil domains of this protein can interact with the coiled-coils of either the movement protein or the aphid transmission factor, thereby mediating both cell-to-cell movement and aphid transmission. The host counters CaMV infection with two lines of defense: innate immunity and silencing. The viral protein 'transactivator/viroplasmin' (TAV) is recognized as an effector and either initiates the innate immunity reaction in a non-permissive host or interferes with it in a permissive host. As a silencing suppressor, TAV interferes with dicing of dsRNAs.

  • a coiled coil interaction mediates Cauliflower Mosaic Virus cell to cell movement
    Proceedings of the National Academy of Sciences of the United States of America, 2005
    Co-Authors: Livia Stavolone, Denis Leclerc, Maria Elena Villani, Thomas Hohn
    Abstract:

    The function of the virion-associated protein (VAP) of Cauliflower Mosaic Virus (CaMV) has long been only poorly understood. VAP is associated with the virion but is dispensable for Virus morphogenesis and replication. It mediates Virus transmission by aphids through simultaneous interaction with both the aphid transmission factor and the virion. However, although insect transmission is not fundamental to CaMV survival, VAP is indispensable for spreading the Virus infection within the host plant. We used a GST pull-down technique to demonstrate that VAP interacts with the viral movement protein through coiled-coil domains and surface plasmon resonance to measure the interaction kinetics. We mapped the movement protein coiled-coil to the C terminus of the protein and proved that it self-assembles as a trimer. Immunogold labeling/electron microscopy revealed that the VAP and viral movement protein colocalize on CaMV particles within plasmodesmata. These results highlight the multifunctional potential of the VAP protein conferred by its efficient coiled-coil interaction system and show a plant Virus possessing a surface-exposed protein (VAP) mediating viral entry into host cells.

  • the Cauliflower Mosaic Virus 35s promoter extends into the transcribed region
    Journal of Virology, 2004
    Co-Authors: Sandra Pauli, Helen M Rothnie, Gang Chen, Thomas Hohn
    Abstract:

    A 60-nucleotide region (S1) downstream of the transcription start site of the Cauliflower Mosaic Virus 35S RNA can enhance gene expression. By using transient expression assays with plant protoplasts, this activity was shown to be at least partially due to the effect of transcriptional enhancers within this region. We identify sequence motifs with enhancer function, which are normally masked by the powerful upstream enhancers of the 35S promoter. A repeated CT-rich motif is involved both in enhancer function and in interaction with plant nuclear proteins. The S1 region can also enhance expression from heterologous promoters.

  • Control of translation reinitiation on the Cauliflower Mosaic Virus (CaMV) polycistronic RNA.
    Biochemical Society Transactions, 2004
    Co-Authors: L. Ryabova, Hyun Sook Park, Thomas Hohn
    Abstract:

    Translation of the polycistronic 35S RNA of CaMV (Cauliflower Mosaic Virus) occurs via a reinitiation mechanism, which requires TAV (transactivator/viroplasmin). To allow translation reinitiation of the major open reading frames on the polycistronic RNA, TAV interacts with the host translational machinery via eIF3 (eukaryotic initiation factor 3) and the 60S ribosome. Accumulation of TAV and eIF3 in the polysomal fraction isolated from CaMV-infected cells suggested that TAV prevents loss of eIF3 from the translating ribosomes during the first initiation event. The TAV–eIF3–80S complex could be detected in vitro by sucrose-gradient-sedimentation analysis. The question is whether TAV interacts directly with the 48S preinitiation complex or enters polysomes after the first initiation event. eIF4B, a component of the 48S initiation complex, can preclude formation of the TAV–eIF3 complex via competition with TAV for eIF3 binding; the eIF4B- and TAV-binding sites on eIF3g overlap. eIF4B out-competes TAV for binding to eIF3 and to the eIF3–40S complex. Transient overexpression of eIF4B in plant protoplasts specifically inhibits TAV-mediated transactivation of polycistronic translation. Our results thus indicate that eIF4B precludes TAV–eIF3–40S complex formation during the first initiation event. Consequently, overexpression of TAV in plant protoplasts affects only the second and subsequent initiation events. We propose a model in which TAV enters the host translational machinery at the eIF4B-removal step to stabilize eIF3 within polysomes.

  • Splicing of Cauliflower Mosaic Virus 35S RNA serves to downregulate a toxic gene product
    Journal of General Virology, 2004
    Co-Authors: Remy Froissart, Thomas Hohn, Martin Drucker, Marilyne Uzest-bonhomme, Virginia Ruiz-ferrer, Eugénie Hébrard, Stéphane Blanc
    Abstract:

    Alternative splicing usually leads to an increase in the number of gene products that can be derived from a single transcript. Here, a different and novel use of alternative splicing - as a means to control the amount of a potentially toxic gene product in the plant pararetroVirus Cauliflower Mosaic Virus (CaMV) - is reported. About 70 % of the CaMV 35S RNA, which serves as a substrate for both reverse transcription and polycistronic mRNA, is spliced into four additional RNA species. Splicing occurs between four donor sites - one in the 5' untranslated region and three within open reading frame (ORF) I - and one unique acceptor site at position 1508 in ORF II. A previous study revealed that the acceptor site is vital for CaMV infectivity and expression of ORFs III and IV from one of the spliced RNA species suggested that splicing may facilitate expression of downstream CaMV ORFs. However, it is shown here that deleting the splice acceptor site and replacing ORF II with a cargo ORF that lacks splice acceptor sites does not interfere with Virus proliferation. Furthermore, it is demonstrated that whenever P2 cannot accumulate in infected tissues, the splice acceptor site at position 1508 is no longer vital and has little effect on Virus replication. This suggests that the vital role of splicing in CaMV is regulation of P2 expression and that P2 exhibits biological properties that, whilst indispensable for Virus-vector interactions, can block in planta Virus infection if this regulation is abolished.

Mario Keller - One of the best experts on this subject based on the ideXlab platform.

  • Cauliflower Mosaic Virus transcriptome reveals a complex alternative splicing pattern
    PLOS ONE, 2015
    Co-Authors: Clement Bouton, Angèle Geldreich, Lyubov A Ryabova, Laetitia Ramel, Maria Dimitrova, Mario Keller
    Abstract:

    The plant pararetroVirus Cauliflower Mosaic Virus (CaMV) uses alternative splic-ing to generate several isoforms from its polycistronic pregenomic 35S RNA. This pro-cess has been shown to be essential for infectivity. Previous works have identified four splice donor sites and a single splice acceptor site in the 35S RNA 5’ region and sug-gested that the main role of CaMV splicing is to downregulate expression of open read-ing frames (ORFs) I and II. In this study, we show that alternative splicing is a conserved process among CaMV isolates. In Cabb B-JI and Cabb-S isolates, splicing frequently leads to different fusion between ORFs, particularly between ORF I and II. The corresponding P1P2 fusion proteins expressed in E. coli interact with viral proteins P2 and P3 in vitro. However, they are detected neither during infection nor upon transient expression in planta, which suggests rapid degradation after synthesis and no important biological role in the CaMV infectious cycle. To gain a better understanding of the functional relevance of 35S RNA alternative splicing in CaMV infectivity, we inactivated the previously described splice sites. All the splicing mutants were as pathogenic as the corresponding wild-type isolate. Through RT-PCR-based analysis we demonstrate that CaMV 35S RNA exhibits a complex splicing pattern, as we identify new splice donor and acceptor sites whose selection leads to more than thirteen 35S RNA isoforms in infected turnip plants. Inactivating splice donor or acceptor sites is not lethal for the Virus, since disrupted sites are systematically rescued by the activation of cryptic and/or seldom used splice sites. Taken together, our data depict a conserved, complex and flexible process, involving multiple sites, that ensures splicing of 35S RNA.

  • p6 protein of Cauliflower Mosaic Virus a translation reinitiator interacts with ribosomal protein l13 from arabidopsis thaliana
    Journal of General Virology, 2004
    Co-Authors: Marina Bureau, Véronique Leh, Pierre Yot, Angèle Geldreich, Muriel Haas, Lyubov A Ryabova, Mario Keller
    Abstract:

    The P6 protein of Cauliflower Mosaic Virus (CaMV) transactivates translation of the CaMV 35S polycistronic pregenomic RNA and its spliced versions, and thus allows synthesis of a complete set of viral proteins. Previous studies have shown that P6 interacts with plant L18 and L24 ribosomal proteins and initiation factor eIF3, and it has been proposed that these interactions are involved in the reinitiation of translation of polycistronic viral RNAs. This study characterizes a novel cellular partner of P6, the ribosomal protein L13 from Arabidopsis thaliana. Far-Western assays performed with several P6 deletion mutants have shown that L13 interacts with the miniTAV of P6, which represents the minimal domain for transactivation, suggesting that the P6–L13 interaction might also be involved in this process. L13 and L18 were found to bind to the same region within the miniTAV. Competition assays between L18 and L13 for binding to miniTAV suggest that interactions between P6 and these ribosomal proteins involve separate P6 molecules, and/or occur at different stages of translation or in the context of another function also mediated by P6.

  • Cauliflower Mosaic Virus still in the news
    Molecular Plant Pathology, 2002
    Co-Authors: Muriel Haas, Angèle Geldreich, Pierre Yot, Marina Bureau, Mario Keller
    Abstract:

    SUMMARY Taxonomic relationship: Cauliflower Mosaic Virus (CaMV) is the type member of the CaulimoVirus genus in the Caulimoviridae family, which comprises five other genera. CaMV replicates its DNA genome by reverse transcription of a pregenomic RNA and thus belongs to the pararetroVirus supergroup, which includes the Hepadnaviridae family infecting vertebrates. Physical properties: Virions are non-enveloped isometric particles, 53 nm in diameter (Fig. 1). They are constituted by 420 capsid protein subunits organized following T= 7 icosahedral symmetry (Cheng, R.H., Olson, N.H. and Baker, T.S. (1992) Cauliflower Mosaic Virus: a 420 subunit (T= 7), multilayer structure. Virology, 16, 655-668). The genome consists of a double-stranded circular DNA of approximately 8000 bp that is embedded in the inner surface of the capsid. Viral proteins: The CaMV genome encodes six proteins, a cell-to-cell movement protein (P1), two aphid transmission factors (P2 and P3), the precursor of the capsid proteins (P4), a polyprotein precursor of proteinase, reverse transcriptase and ribonuclease H (P5) and an inclusion body protein/translation transactivator (P6). Hosts: The host range of CaMV is limited to plants of the Cruciferae family, i.e. Brassicae species and Arabidopsis thaliana, but some viral strains can also infect solanaceous plants. In nature, CaMV is transmitted by aphids in a non-circulative manner.

  • the Cauliflower Mosaic Virus translational transactivator interacts with the 60s ribosomal subunit protein l18 of arabidopsis thaliana
    Virology, 2000
    Co-Authors: Mario Keller
    Abstract:

    Abstract The Cauliflower Mosaic Virus (CaMV) open reading frame VI product (P6) is involved in several aspects of the infectious cycle. P6 specifically controls the synthesis of other CaMV proteins by transactivating their expression from the polycistronic 35S RNA. By far-Western assays, we have demonstrated that P6 interacts with proteins from both healthy and CaMV-infected leaves of Arabidopsis thaliana. These proteins are found in ribosome-enriched extracts, suggesting that they participate in the translation process. One of these proteins, identified by microsequencing, corresponds to the 60S ribosomal subunit protein L18 (RPL18). Its cDNA was cloned and expressed in Escherichia coli, and the resulting RPL18 protein was shown to interact with the minimal region required for translational transactivation, designated the miniTAV domain of P6.

  • The Cauliflower Mosaic Virus translational transactivator interacts with the 60S ribosomal subunit protein L18 of Arabidopsis thaliana
    Virology, 2000
    Co-Authors: Véronique Leh, Pierre Yot, Mario Keller
    Abstract:

    The Cauliflower Mosaic Virus (CaMV) open reading frame VI product (P6) is involved in several aspects of the infectious cycle. P6 specifically controls the synthesis of other CaMV proteins by transactivating their expression from the polycistronic 35S RNA. By far-Western assays, we have demonstrated that P6 interacts with proteins from both healthy and CaMV-infected leaves of Arabidopsis thaliana. These proteins are found in ribosome-enriched extracts, suggesting that they participate in the translation process. One of these proteins, identified by microsequencing, corresponds to the 60S ribosomal subunit protein L18 (RPL18). Its cDNA was cloned and expressed in Escherichia coli, and the resulting RPL18 protein was shown to interact with the minimal region required for translational transactivation, designated the miniTAV domain of P6.

Stéphane Blanc - One of the best experts on this subject based on the ideXlab platform.

  • Structure of the Cauliflower Mosaic Virus P2 protein: insight into molecular mechanism of transmission
    2019
    Co-Authors: François Hoh, Stéphane Blanc, Marilyne Uzest, Chloé Fallet, Aurélie Ancelin, Josephine Lai-kee-him, Stefano Trapani, Patrick Bron
    Abstract:

    The Cauliflower Mosaic Virus (CaMV) is the member type of the family Caulimoviridae (genus CaulimoVirus) which, together with hepadnaViruses, constitute the para-phylletic group of pararetroViruses having a DNA-based genome replicated via reverse transcription of a pre-genomic RNA. The approximately 8 kpb circular double-stranded DNA genome of CaMV encodes eight major open reading frames. CaMV is transmitted from plant to plant through a seemingly simple interaction with insect vectors. This process involves an aphid receptor and two viral proteins, P2 and P3. P2 binds to both the aphid receptor and P3, itself tightly associated with the Virus particle, with the ensemble forming a transmissible viral complex. Additionally, the viral complex is also able to bind microtubules through P2, allowing a rapid spreading of the Virus into plant cells and consequently its uptake by the insect. In the present study, we report an integrated structural characterization of P2. We succeeded in production, purification and crystallisation of a P2 mutant corresponding to a deletion of the first coiled-coil helix α1. The structure shows clearly two completely independent domains in which a central core is formed by four coiled-coil α-helix, surrounded by 4 short ß sheets. These data combined with our results obtained by cryo-electron microscopy of P2-decorated microtubules and cryo-electron tomography of P2 para-crystals allow us to gain new insight into molecular mechanism of transmission.

  • Interactions Between Drought and Plant Genotype Change Epidemiological Traits of Cauliflower Mosaic Virus
    Frontiers in Plant Science, 2018
    Co-Authors: Sandy Berges, Stéphane Blanc, Denis Vile, Cecilia Vazquez Rovere, Michel Yvon, Alexis Bediee, Gaelle Rolland, Myriam Dauzat, Manuella Van Munster
    Abstract:

    Plants suffer from a broad range of abiotic and biotic stresses that do not occur in isolation but often simultaneously. Productivity of natural and agricultural systems is frequently constrained by water limitation, and the frequency and duration of drought periods will likely increase due to global climate change. In addition, phytoViruses represent highly prevalent biotic threat in wild and cultivated plant species. Several hints support a modification of epidemiological parameters of plant Viruses in response to environmental changes but a clear quantification of plant-Virus interactions under abiotic stresses is still lacking. Here we report the effects of a water deficit on epidemiological parameters of Cauliflower Mosaic Virus (CaMV), a non-circulative Virus transmitted by aphid vectors, in nine natural accessions of Arabidopsis thaliana with known contrasted responses to water deficit. Plant growth-related traits and Virus epidemiological parameters were evaluated in PHENOPSIS, an automated high throughput phenotyping platform. Water deficit had contrasted effects on CaMV transmission rate and viral load among A. thaliana accessions. Under well-watered conditions, transmission rate tended to increase with viral load and with CaMV virulence across accessions. Under water deficit, transmission rate and virulence were negatively correlated. Changes in the rate of transmission under water deficit were not related to changes in viral load. Our results support the idea that optimal virulence of a given Virus, as hypothesized under the transmission-virulence trade-off, is highly dependent on the environment and growth traits of the host.

  • multiples fonctions des usines virales l exemple du Virus de la mosaique du chou fleur Cauliflower Mosaic Virus
    Virologie, 2014
    Co-Authors: Aurélie Bak, Daniel Gargani, Stéphane Blanc, Alexandre Martiniere, Martin Drucker
    Abstract:

    Many Viruses form inclusion bodies in infected plant and mammalian cells. Their formation often requires membrane rearrangement of various organelles, but some inclusions form in the cytoplasm independently of the endomembrane system. In the latter case, they may resemble aggresomes or stress bodies but many inclusions do not seem to be related to any cellular structures. Synthesis, composition and size of these inclusions change with Virus species. The best characterized inclusions create a "viral organelle" protecting Viruses from host defenses and optimizing viral replication and assembly. These inclusions are also called viral factories. Recently, more complex and original functions were described for viral factories. This is exemplified here for Cauliflower Mosaic Virus (CaMV) factories. Unexpectedly, besides replication, CaMV factories also participate in another crucial step of the viral cycle: vector-transmission by aphids.

  • Virus Factories of Cauliflower Mosaic Virus Are Virion Reservoirs That Engage Actively in Vector Transmission
    Journal of Virology, 2013
    Co-Authors: Aurélie Bak, Jean Luc Macia, Daniel Gargani, Stéphane Blanc, Enrick Malouvet, Marie-stéphanie Vernerey, Martin Drucker
    Abstract:

    ABSTRACT Cauliflower Mosaic Virus (CaMV) forms two types of inclusion bodies within infected plant cells: numerous Virus factories, which are the sites for viral replication and virion assembly, and a single transmission body (TB), which is specialized for Virus transmission by aphid vectors. The TB reacts within seconds to aphid feeding on the host plant by total disruption and redistribution of its principal component, the viral transmission helper protein P2, onto microtubules throughout the cell. At the same time, virions also associate with microtubules. This redistribution of P2 and virions facilitates transmission and is reversible; the TB reforms within minutes after vector departure. Although some virions are present in the TB before disruption, their subsequent massive accumulation on the microtubule network suggests that they also are released from Virus factories. Using drug treatments, mutant Viruses, and exogenous supply of viral components to infected protoplasts, we show that virions can rapidly exit Virus factories and, once in the cytoplasm, accumulate together with the helper protein P2 on the microtubule network. Moreover, we show that during reversion of this phenomenon, virions from the microtubule network can either be incorporated into the reverted TB or return to the Virus factories. Our results suggest that CaMV factories are dynamic structures that participate in vector transmission by controlled release and uptake of virions during TB reaction.

  • Structural Insights into the Molecular Mechanisms of Cauliflower Mosaic Virus Transmission by Its Insect Vector
    Journal of Virology, 2010
    Co-Authors: Marilyne Uzest, Stéphane Blanc, Martin Drucker, Célia Plisson-chastang, Patrick Bron, Christian Dumas
    Abstract:

    Cauliflower Mosaic Virus (CaMV) is transmitted from plant to plant through a seemingly simple interaction with insect vectors. This process involves an aphid receptor and two viral proteins, P2 and P3. P2 binds to both the aphid receptor and P3, itself tightly associated with the Virus particle, with the ensemble forming a transmissible viral complex. Here, we describe the conformations of both unliganded CaMV P3 protein and its virion-associated form. X-ray crystallography revealed that the N-terminal domain of unliganded P3 is a tetrameric parallel coiled coil with a unique organization showing two successive four-stranded subdomains with opposite supercoiling handedness stabilized by a ring of interchain disulfide bridges. A structural model of Virus-liganded P3 proteins, folding as an antiparallel coiled-coil network coating the Virus surface, was derived from molecular modeling. Our results highlight the structural and biological versatility of this coiled-coil structure and provide new insights into the molecular mechanisms involved in CaMV acquisition and transmission by the insect vector.

Pierre Yot - One of the best experts on this subject based on the ideXlab platform.

  • p6 protein of Cauliflower Mosaic Virus a translation reinitiator interacts with ribosomal protein l13 from arabidopsis thaliana
    Journal of General Virology, 2004
    Co-Authors: Marina Bureau, Véronique Leh, Pierre Yot, Angèle Geldreich, Muriel Haas, Lyubov A Ryabova, Mario Keller
    Abstract:

    The P6 protein of Cauliflower Mosaic Virus (CaMV) transactivates translation of the CaMV 35S polycistronic pregenomic RNA and its spliced versions, and thus allows synthesis of a complete set of viral proteins. Previous studies have shown that P6 interacts with plant L18 and L24 ribosomal proteins and initiation factor eIF3, and it has been proposed that these interactions are involved in the reinitiation of translation of polycistronic viral RNAs. This study characterizes a novel cellular partner of P6, the ribosomal protein L13 from Arabidopsis thaliana. Far-Western assays performed with several P6 deletion mutants have shown that L13 interacts with the miniTAV of P6, which represents the minimal domain for transactivation, suggesting that the P6–L13 interaction might also be involved in this process. L13 and L18 were found to bind to the same region within the miniTAV. Competition assays between L18 and L13 for binding to miniTAV suggest that interactions between P6 and these ribosomal proteins involve separate P6 molecules, and/or occur at different stages of translation or in the context of another function also mediated by P6.

  • Cauliflower Mosaic Virus still in the news
    Molecular Plant Pathology, 2002
    Co-Authors: Muriel Haas, Angèle Geldreich, Pierre Yot, Marina Bureau, Mario Keller
    Abstract:

    SUMMARY Taxonomic relationship: Cauliflower Mosaic Virus (CaMV) is the type member of the CaulimoVirus genus in the Caulimoviridae family, which comprises five other genera. CaMV replicates its DNA genome by reverse transcription of a pregenomic RNA and thus belongs to the pararetroVirus supergroup, which includes the Hepadnaviridae family infecting vertebrates. Physical properties: Virions are non-enveloped isometric particles, 53 nm in diameter (Fig. 1). They are constituted by 420 capsid protein subunits organized following T= 7 icosahedral symmetry (Cheng, R.H., Olson, N.H. and Baker, T.S. (1992) Cauliflower Mosaic Virus: a 420 subunit (T= 7), multilayer structure. Virology, 16, 655-668). The genome consists of a double-stranded circular DNA of approximately 8000 bp that is embedded in the inner surface of the capsid. Viral proteins: The CaMV genome encodes six proteins, a cell-to-cell movement protein (P1), two aphid transmission factors (P2 and P3), the precursor of the capsid proteins (P4), a polyprotein precursor of proteinase, reverse transcriptase and ribonuclease H (P5) and an inclusion body protein/translation transactivator (P6). Hosts: The host range of CaMV is limited to plants of the Cruciferae family, i.e. Brassicae species and Arabidopsis thaliana, but some viral strains can also infect solanaceous plants. In nature, CaMV is transmitted by aphids in a non-circulative manner.

  • The Cauliflower Mosaic Virus translational transactivator interacts with the 60S ribosomal subunit protein L18 of Arabidopsis thaliana
    Virology, 2000
    Co-Authors: Véronique Leh, Pierre Yot, Mario Keller
    Abstract:

    The Cauliflower Mosaic Virus (CaMV) open reading frame VI product (P6) is involved in several aspects of the infectious cycle. P6 specifically controls the synthesis of other CaMV proteins by transactivating their expression from the polycistronic 35S RNA. By far-Western assays, we have demonstrated that P6 interacts with proteins from both healthy and CaMV-infected leaves of Arabidopsis thaliana. These proteins are found in ribosome-enriched extracts, suggesting that they participate in the translation process. One of these proteins, identified by microsequencing, corresponds to the 60S ribosomal subunit protein L18 (RPL18). Its cDNA was cloned and expressed in Escherichia coli, and the resulting RPL18 protein was shown to interact with the minimal region required for translational transactivation, designated the miniTAV domain of P6.

  • aphid transmission of Cauliflower Mosaic Virus requires the viral piii protein
    The EMBO Journal, 1999
    Co-Authors: Véronique Leh, Pierre Yot, Emmanuel Jacquot, Angèle Geldreich, Thomas Hermann, Denis Leclerc, Martine Cerutti, Mario Keller
    Abstract:

    The open reading frame (ORF) III product (PIII) of Cauliflower Mosaic Virus is necessary for the infection cycle but its role is poorly understood. We have used in vitro protein binding (‘far Western’) assays to demonstrate that PIII interacts with the Cauliflower Mosaic Virus (CaMV) ORF II product (PII), a known aphid transmission factor. Aphid transmission of purified virions of the PII-defective strain CM4-184 was dependent upon added PII, but complementation was efficient only in the presence of PIII, demonstrating the requirement of PIII for transmission. Deletion mutagenesis mapped the interaction domains of PIII and PII to the 30 N-terminal and 61 C-terminal residues of PIII and PII, respectively. A model for interaction between PIII and PII is proposed on the basis of secondary structure predictions. Finally, a direct correlation between the ability of PIII and PII to interact and aphid transmissibility of the Virus was demonstrated by using mutagenized PIII proteins. Taken together, these data argue strongly that PIII is a second ‘helper’ factor required for CaMV transmission by aphids.

  • Mapping regions of the Cauliflower Mosaic Virus ORF III product required for infectivity.
    Virology, 1998
    Co-Authors: Emmanuel Jacquot, Mario Keller, Angèle Geldreich, Pierre Yot
    Abstract:

    Abstract The open reading frame (ORF) III product (PIII) of the pararetroVirus Cauliflower Mosaic Virus (CaMV) has nucleic acid-binding properties in vitro, but its biological role is not yet determined. ORF III is closely linked to ORF II and overlaps ORF IV out of frame in the CaMV genome. A new CaMV-derived vector (CaΔ) devoid of ORF III and containing unique restriction sites between ORFs II and IV was designed. Introduction of the wild-type CaMV ORF III into CaΔ results in a clone (Ca3) infectious in turnip plants. Truncated or point-mutated versions of ORF III were then inserted into CaΔ and tested in vivo. Inoculation of the different mutants into turnip revealed that the four C-terminal amino acid residues of PIII are dispensable for infectivity as well as an internal domain (amino acids 61 to 80). Taken together the results show that PIII possesses a functional two-domain organization. Moreover, the CaMV PIII function(s) cannot be replaced either by the PIII protein of another caulimoVirus, the figwort Mosaic Virus, or by the P2 protein of the cacao swollen shoot badnaVirus, a member of the second plant pararetroVirus group.

James E Schoelz - One of the best experts on this subject based on the ideXlab platform.

  • Cauliflower Mosaic Virus p6 inclusion body formation a dynamic and intricate process
    Virology, 2021
    Co-Authors: Roberto Alersvelazquez, James E Schoelz, Sarah Jacques, Clare Muller, Jennifer K Boldt, Scott Leisner
    Abstract:

    During an infection, Cauliflower Mosaic Virus (CaMV) forms inclusion bodies (IBs) mainly composed of viral protein P6, where viral activities occur. Because viral processes occur in IBs, understanding the mechanisms by which they are formed is crucial. FL-P6 expressed in N. benthamiana leaves formed IBs of a variety of shapes and sizes. Small IBs were dynamic, undergoing fusion/dissociation events. Co-expression of actin-binding polypeptides with FL-P6 altered IB size distribution and inhibited movement. This suggests that IB movement is required for fusion and growth. A P6 deletion mutant was discovered that formed a single large IB per cell, which suggests it exhibited altered fusion/dissociation dynamics. Myosin-inhibiting drugs did not affect small IB movement, while those inhibiting actin polymerization did. Large IBs colocalized with components of the aggresome pathway, while small ones generally did not. This suggests a possible involvement of the aggresome pathway in large IB formation.

  • Setting Up Shop: The Formation and Function of the Viral Factories of Cauliflower Mosaic Virus
    Frontiers Media S.A., 2017
    Co-Authors: James E Schoelz, Scott Leisner
    Abstract:

    Similar to cells, Viruses often compartmentalize specific functions such as genome replication or particle assembly. Viral compartments may contain host organelle membranes or they may be mainly composed of viral proteins. These compartments are often termed: inclusion bodies (IBs), viroplasms or viral factories. The same Virus may form more than one type of IB, each with different functions, as illustrated by the plant pararetroVirus, Cauliflower Mosaic Virus (CaMV). CaMV forms two distinct types of IBs in infected plant cells, those composed mainly of the viral proteins P2 (which are responsible for transmission of CaMV by insect vectors) and P6 (required for viral intra-and inter-cellular infection), respectively. P6 IBs are the major focus of this review. Much of our understanding of the formation and function of P6 IBs comes from the analyses of their major protein component, P6. Over time, the interactions and functions of P6 have been gradually elucidated. Coupled with new technologies, such as fluorescence microscopy with fluorophore-tagged viral proteins, these data complement earlier work and provide a clearer picture of P6 IB formation. As the activities and interactions of the viral proteins have gradually been determined, the functions of P6 IBs have become clearer. This review integrates the current state of knowledge on the formation and function of P6 IBs to produce a coherent model for the activities mediated by these sophisticated Virus-manufacturing machines

  • a model for intracellular movement of Cauliflower Mosaic Virus the concept of the mobile virion factory
    Journal of Experimental Botany, 2016
    Co-Authors: James E Schoelz, Carlos A Angel, Richard S Nelson, Scott Leisner
    Abstract:

    The genomes of many plant Viruses have a coding capacity limited to <10 proteins, yet it is becoming increasingly clear that individual plant Virus proteins may interact with several targets in the host for establishment of infection. As new functions are uncovered for individual viral proteins, virologists have realized that the apparent simplicity of the Virus genome is an illusion that belies the true impact that plant Viruses have on host physiology. In this review, we discuss our evolving understanding of the function of the P6 protein of Cauliflower Mosaic Virus (CaMV), a process that was initiated nearly 35 years ago when the CaMV P6 protein was first described as the 'major inclusion body protein' (IB) present in infected plants. P6 is now referred to in most articles as the transactivator (TAV)/viroplasmin protein, because the first viral function to be characterized for the CaulimoVirus P6 protein beyond its role as an inclusion body protein (the viroplasmin) was its role in translational transactivation (the TAV function). This review will discuss the currently accepted functions for P6 and then present the evidence for an entirely new function for P6 in intracellular movement.

  • the p6 protein of Cauliflower Mosaic Virus interacts with chup1 a plant protein which moves chloroplasts on actin microfilaments
    Virology, 2013
    Co-Authors: Carlos A Angel, Scott Leisner, Richard S Nelson, Lindy Lutz, Xiaohua Yang, Andres Rodriguez, Adam Adair, Yu Zhang, James E Schoelz
    Abstract:

    The gene VI product, protein 6 (P6), of Cauliflower Mosaic Virus (CaMV) assembles into large, amorphous inclusion bodies (IBs) that are considered sites for viral protein synthesis and viral genome replication and encapsidation. P6 IBs align with microfilaments and require them for intracellular trafficking, a result implying that P6 IBs function to move Virus complexes or virions within the cell to support Virus physiology. Through a yeast two-hybrid screen we determined that CHUP1, a plant protein allowing chloroplast transport through an interaction with chloroplast and microfilament, interacts with P6. The interaction between CHUP1 and P6 was confirmed through colocalization in vivo and co-immunoprecipitation assays. A truncated CHUP1 fused with enhanced cyan fluorescent protein, unable to transport chloroplasts, inhibited intracellular movement of P6–Venus inclusions. Silencing of CHUP1 in N. edwardsonii impaired the ability of CaMV to infect plants. The findings suggest that CHUP1 supports CaMV infection through an interaction with P6.

  • uncoupling resistance from cell death in the hypersensitive response of nicotiana species to Cauliflower Mosaic Virus infection
    Molecular Plant-microbe Interactions, 2001
    Co-Authors: Anthony B Cole, Lorant Kiraly, Kathleen Ross, James E Schoelz
    Abstract:

    Cauliflower Mosaic Virus strain W260 elicits a hypersensitive response (HR) in leaves of Nicotiana edwardsonii, an interspecific hybrid derived from a cross between N. glutinosa and N. clevelandii. Interestingly, we found that N. glutinosa is resistant to W260, but responds with local chlorotic lesions rather than necrotic lesions. In contrast, N. clevelandii responds to W260 with systemic cell death. The reactions of the progenitors of N. edwardsonii to W260 infection indicated that each contributed a factor toward the development of HR. In this study, we present two lines of evidence to show that the resistance and cell death that comprise the HR elicited by W260 can indeed be uncoupled. First, we showed that the non-necrotic resistance response of N. glutinosa could be converted to HR when these plants were crossed with N. clevelandii. Second, we found that cell death and resistance segregated independently in the F2 population of a cross between N. edwardsonii and N. clevelandii. We concluded that the...