scholarly journals Evidence of a cellulosic layer in Pandoravirus tegument and the mystery of the genetic support of its biosynthesis

2019 ◽  
Author(s):  
Djamal Brahim Belhaouari ◽  
Jean-Pierre Baudoin ◽  
Franck Gnankou ◽  
Fabrizio Di Pinto ◽  
Philippe Colson ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Cellulose Synthase ◽  
Cellulose Synthesis ◽  
Dense Layer ◽  
Gene Encoding ◽  
Calcofluor White ◽  
Dense Membrane ◽  
Giant Viruses ◽  
Helicoidal Structure ◽  
The One

AbstractPandoraviruses are giant viruses of amoebae with 1 μm-long virions. They have an ovoid morphology and are surrounded by a tegument-like structure lacking any capsid protein nor any gene encoding a capsid protein. In this work, we studied the ultrastructure of the tegument surrounding Pandoravirus massiliensis virions and noticed that this tegument is composed of a peripheral sugar layer, an electron-dense membrane, and a thick electron-dense layer consisting in several tubules arranged in a helicoidal structure resembling that of cellulose. Pandoravirus massiliensis particles were stained by Calcofluor white, a fluorescent dye of cellulose, and the enzymatic treatment of particles by cellulase showed the degradation of the viral tegument. We first hypothesized that the cellulose tegument could be synthesized by enzymes encoded by Pandoravirus. Bioinformatic analyses revealed in Pandoravirus massiliensis, a candidate gene encoding a putative cellulose synthase, with a homology with the BcsA domain, one of the catalytic subunits of the bacterial cellulose synthase, but with a low level of homology. This gene was transcribed during the replicative cycle of Pandoravirus massiliensis, but several arguments run counter to this hypothesis. Indeed, even if this gene is present in other Pandoraviruses, the one of the strain studied is the only one to have this BcsA domain and no other enzymes involved in the synthesis of cellulose could be detected, although we cannot rule out that such genes could have been undetected among the large proportion of Orfans of Pandoraviruses. As an alternative, we investigated whether Pandoravirus could divert the cellulose synthesis machinery of the amoeba to its own account. Indeed, contrary to what is observed in the case of infections with other giant viruses such as mimivirus, it appears that the transcription of the amoeba, at least for the cellulose synthase gene, continues throughout the growth phase of envelopes of Pandoravirus. Finally, we believe that this scenario is more plausible. If confirmed, it could be a unique mechanism in the virosphere.

scholarly journals Inducible Gene Expression from African Swine Fever Virus Recombinants: Analysis of the Major Capsid Protein p72

1998 ◽  
Vol 72 (4) ◽  
pp. 3185-3195 ◽  
Author(s):  
Ramón García-Escudero ◽  
Germán Andrés ◽  
Fernando Almazán ◽  
Eladio Viñuela
Keyword(s):  
Capsid Protein ◽  
Major Capsid Protein ◽  
African Swine Fever Virus ◽  
Expression System ◽  
African Swine Fever ◽  
Firefly Luciferase ◽  
Fever Virus ◽  
Gene Encoding ◽  
Iptg Induction ◽  
Dense Membrane

ABSTRACT A method to study the function of individual African swine fever virus (ASFV) gene products utilizing the Escherichia coli lac repressor-operator system has been developed. Recombinant viruses containing both the lacI gene encoding thelac repressor and a strong virus late promoter modified by the insertion of one or two copies of the lac operator sequence at various positions were constructed. The ability of each modified promoter to regulate expression of the firefly luciferase gene was assayed in the presence and in the absence of the inducer isopropyl β-d-thiogalactoside (IPTG). Induction and repression of gene activity were dependent on the position(s) of the operator(s) with respect to the promoter and on the number of operators inserted. The ability of this system to regulate the expression of ASFV genes was analyzed by constructing a recombinant virus inducibly expressing the major capsid protein p72. Electron microscopy analysis revealed that under nonpermissive conditions, electron-dense membrane-like structures accumulated in the viral factories and capsid formation was inhibited. Induction of p72 expression allowed the progressive building of the capsid on these structures, leading to assembly of ASFV particles. The results of this report demonstrate that the transferred inducible expression system is a powerful tool for analyzing the function of ASFV genes.

scholarly journals Disruption of Very-Long-Chain-Fatty Acid Synthesis Has an Impact on the Dynamics of Cellulose Synthase in Arabidopsis thaliana

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1599
Author(s):  
Xiaoyu Zhu ◽  
Frédérique Tellier ◽  
Ying Gu ◽  
Shundai Li
Keyword(s):  
Fatty Acid ◽  
Cell Biology ◽  
Higher Plants ◽  
Threshold Level ◽  
Cellulose Synthase ◽  
Chain Fatty Acid ◽  
Cellulose Synthesis ◽  
Cellulose Content ◽  
Long Chain Fatty Acid ◽  
Long Chain

In higher plants, cellulose is synthesized by membrane-spanning large protein complexes named cellulose synthase complexes (CSCs). In this study, the Arabidopsis PASTICCINO2 (PAS2) was identified as an interacting partner of cellulose synthases. PAS2 was previously characterized as the plant 3-hydroxy-acyl-CoA dehydratase, an ER membrane-localized dehydratase that is essential for very-long-chain-fatty acid (VLCFA) elongation. The pas2-1 mutants show defective cell elongation and reduction in cellulose content in both etiolated hypocotyls and light-grown roots. Although disruption of VLCFA synthesis by a genetic alteration had a reduction in VLCFA in both etiolated hypocotyls and light-grown roots, it had a differential effect on cellulose content in the two systems, suggesting the threshold level of VLCFA for efficient cellulose synthesis may be different in the two biological systems. pas2-1 had a reduction in both CSC delivery rate and CSC velocity at the PM in etiolated hypocotyls. Interestingly, Golgi but not post-Golgi endomembrane structures exhibited a severe defect in motility. Experiments using pharmacological perturbation of VLCFA content in etiolated hypocotyls strongly indicate a novel function of PAS2 in the regulation of CSC and Golgi motility. Through a combination of genetic, biochemical and cell biology studies, our study demonstrated that PAS2 as a multifunction protein has an important role in the regulation of cellulose biosynthesis in Arabidopsis hypocotyl.

scholarly journals A mutation in the catalytic domain of cellulose synthase 6 halts its transport to the Golgi apparatus

2019 ◽  
Vol 70 (21) ◽  
pp. 6071-6083 ◽  
Author(s):  
Sungjin Park ◽  
Bo Song ◽  
Wei Shen ◽  
Shi-You Ding
Keyword(s):  
Golgi Apparatus ◽  
Catalytic Domain ◽  
Cellulose Synthase ◽  
Cellulose Synthesis ◽  
Normal Transport

D395N in the catalytic domain of CESA6 interrupts its normal transport to the Golgi, which hampers its function in cellulose synthesis.

scholarly journals The 4.4 Å structure of the giant Melbournevirus virion belonging to the Marseilleviridae family

2021 ◽  
Author(s):  
Raymond N Burton-Smith ◽  
Hemanth K N Reddy ◽  
Martin Svenda ◽  
Chantal Abergel ◽  
Kenta Okamoto ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Capsid Protein ◽  
Major Capsid Protein ◽  
Capsid Proteins ◽  
Atomic Model ◽  
Penton Base ◽  
Cryo Electron Microscopy ◽  
Internal Membrane ◽  
Structural Details ◽  
Giant Viruses

Members of Marseilleviridae, one family of icosahedral giant viruses classified in 2012 have been identified worldwide in all types of environments. The virion shows a characteristic internal membrane extrusion at the five-fold vertices of the capsid, but its structural details need to be elucidated. We now report the 4.4 Å cryo-electron microscopy structure of the Melbournevirus capsid. An atomic model of the major capsid protein (MCP) shows a unique cup structure on the trimer that accommodates additional proteins. A polyalanine model of the penton base protein shows internally extended N- and C-terminals, which indirectly connect to the internal membrane extrusion. The Marseilleviruses share the same orientational organisation of the MCPs as PBCV-1 and CroV, but do not appear to possess a protein akin to the ″tape measure″ of these viruses. Minor capsid proteins named PC-β, zipper, and scaffold are proposed to control the dimensions of the capsid during assembly.

scholarly journals Identification of Putative Cell Wall Synthesis Genes in Betula pendula

2020 ◽  
Author(s):  
Song Chen ◽  
Xin Lin ◽  
Xiyang Zhao ◽  
Su Chen
Keyword(s):  
Cell Wall ◽  
Betula Pendula ◽  
Secondary Cell Wall ◽  
Plant Cell Wall ◽  
Gene Families ◽  
Cellulose Synthase ◽  
Wall Structure ◽  
Cellulose Synthesis ◽  
Cell Wall Synthesis ◽  
Secondary Cell Wall Synthesis

Abstract BackgroundCellulose is an essential structural component of plant cell wall and is an important resource to produce paper, textiles, bioplastics and other biomaterials. The synthesis of cellulose is among the most important but poorly understood biochemical processes, which is precisely regulated by internal and external cues.ResultsHere, we identified 46 gene models in 7 gene families which encoding cellulose synthase and related enzymes of Betula pendula, and the transcript abundance of these genes in xylem, root, leaf and flower tissues also be determined. Based on these RNA-seq data, we have identified 8 genes that most likely participate in secondary cell wall synthesis, which include 3 cellulose synthase genes and 5 cellulose synthase-like genes. In parallel, a gene co-expression network was also constructed based on transcriptome sequencing.ConclusionsIn this study, we have identified a total of 46 cell wall synthesis genes in B. pendula, which include 8 secondary cell wall synthesis genes. These analyses will help decipher the genetic information of the cell wall synthesis genes, elucidate the molecular mechanism of cellulose synthesis and understand the cell wall structure in B. pendula.

scholarly journals Three Distinct Rice Cellulose Synthase Catalytic Subunit Genes Required for Cellulose Synthesis in the Secondary Wall

2003 ◽  
Vol 133 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Katsuyuki Tanaka ◽  
Kazumasa Murata ◽  
Muneo Yamazaki ◽  
Katsura Onosato ◽  
Akio Miyao ◽  
...  
Keyword(s):  
Secondary Wall ◽  
Cellulose Synthase ◽  
Catalytic Subunit ◽  
Cellulose Synthesis

scholarly journals Role of Capsid Anchor in the Morphogenesis of Zika Virus

2018 ◽  
Vol 92 (22) ◽  
Author(s):  
Jyoti Rana ◽  
José Luis Slon Campos ◽  
Gabriella Leccese ◽  
Maura Francolini ◽  
Marco Bestagno ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Zika Virus ◽  
Protein C ◽  
Transmembrane Domain ◽  
Viral Envelope ◽  
Signal Peptidase ◽  
C Terminus ◽  
Cytosolic Side ◽  
The One

ABSTRACTThe flavivirus capsid protein (C) is separated from the downstream premembrane (PrM) protein by a hydrophobic sequence named capsid anchor (Ca). During polyprotein processing, Ca is sequentially cleaved by the viral NS2B/NS3 protease on the cytosolic side and by signal peptidase on the luminal side of the endoplasmic reticulum (ER). To date, Ca is considered important mostly for directing translocation of PrM into the ER lumen. In this study, the role of Ca in the assembly and secretion of Zika virus was investigated using a pseudovirus-based approach. Our results show that, while Ca-mediated anchoring of C to the ER membrane is not needed for the production of infective particles, Ca expression inciswith respect to PrM is strictly required to allow proper assembly of infectious particles. Finally, we show that the presence of heterologous, but not homologous, Ca induces degradation of E through the autophagy/lysosomal pathway.IMPORTANCEThe capsid anchor (Ca) is a single-pass transmembrane domain at the C terminus of the capsid protein (C) known to function as a signal for the translocation of PrM into the ER lumen. The objective of this study was to further examine the role of Ca in Zika virus life cycle, whether involved in the formation of nucleocapsid through association with C or in the formation of viral envelope. In this study, we show that Ca has a function beyond the one of translocation signal, controlling protein E stability and therefore its availability for assembly of infectious particles.

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