Identification of Specific Cucumber Necrosis Virus Coat Protein Amino Acids Affecting Fungus Transmission and Zoospore Attachment

Kakani, Kishore; Sgro, Jean-Yves; Rochon, D’Ann

doi:10.1128/jvi.75.12.5576-5583.2001

Cited by 49 publications

(68 citation statements)

References 34 publications

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“…More recently, it has been shown that a cavity at the quasi-threefold axis is important in CNV attachment and transmission (12). In this study, we wished to determine whether the acquisition and subsequent transmission of CNV by O. bornovanus involves specific zoospore receptors.…”

mentioning

confidence: 99%

Evidence that Binding of Cucumber Necrosis Virus to Vector Zoospores Involves Recognition of Oligosaccharides

Kakani

Robbins

Rochon

2003

J Virol

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mentioning

confidence: 99%

Evidence that Binding of Cucumber Necrosis Virus to Vector Zoospores Involves Recognition of Oligosaccharides

Kakani

Robbins

Rochon

2003

J Virol

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“…Genetic studies have revealed that specific viral capsid protein domains and amino acids are determinative for transmissibility and vector specificity. Examples can be found for aphid-transmitted viruses in the genera Potyvirus (1,2,11), Luteovirus (53), Polerovirus (3), Enamovirus (7), and Cucumovirus (35,36,44); for the nematode-transmitted viruses in the genus Tobravirus (25); and for fungus-transmitted viruses in the genera Tombusvirus (18,40) and Benyvirus (52). An emerging theme for a number of these viruses is that a minor capsid protein readthrough protein plays an important role in transmission; this protein is generated by a mechanism involving readthrough of the major capsid protein stop codon (reviewed in reference 4).…”

mentioning

confidence: 99%

A Conserved Capsid Protein Surface Domain of Cucumber Mosaic Virus Is Essential for Efficient Aphid Vector Transmission

Liu

Park

et al. 2002

J Virol

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A prominent feature on the surfaces of virions of Cucumber mosaic virus (CMV) is a negatively charged loop structure (the ␤H-␤I loop). Six of 8 amino acids in this capsid protein loop are highly conserved among strains of CMV and other cucumoviruses. Five of these amino acids were individually changed to alanine or lysine (an amino acid of opposite charge) to create nine mutants (the D191A, D191K, D192A, D192K, L194A, E195A, E195K, D197A, and D197K mutants). Transcripts of cDNA clones were infectious when they were mechanically inoculated onto tobacco, giving rise to symptoms of a mottle-mosaic typical of the wild-type virus (the D191A, D191K, D192A, E195A, E195K, and D197A mutants), a systemic necrosis (the D192K mutant), or an atypical chlorosis with necrotic flecking (the L194A mutant). The mutants formed virions and accumulated to wild-type levels, but eight of the nine mutants were defective in aphid vector transmission. The aspartate-to-lysine mutation at position 197 interfered with infection; the only recovered progeny (the D197K‫ء‬ mutant) harbored a second-site mutation (denoted by the asterisk) of alanine to glutamate at position 193, a proximal site in the ␤H-␤I loop. Since the disruption of charged amino acid residues in the ␤H-␤I loop reduces or eliminates vector transmissibility without grossly affecting infectivity or virion formation, we hypothesize that this sequence or structure has been conserved to facilitate aphid vector transmission.

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“…It seems unlikely that the V295A mutation would cause major conformational changes in the P domain. It is important to note that neither mutation drastically affects capsid stability or assembly (21). Interestingly, these residues are on the P domain surface that rises up immediately adjacent to the knob on the shell domain that contains the N109D mutation.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, P73 Location of mutations causing defective transmission. Mechanically passaged CNV isolates were screened for mutants that were defective in fungal transmission and then the mutations were confirmed by site-directed mutagenesis (21). With the atomic structure of CNV, the location of these mutations can be mapped to try to understand how they might affect zoospore binding and transmission ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

Kakani

Katpally

et al. 2013

J Virol

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Cucumber necrosis virus (CNV) is a member of the genus Tombusvirus and has a monopartite positive-sense RNA genome packaged in a T‫3؍‬ icosahedral particle. CNV is transmitted in nature via zoospores of the fungus Olpidium bornovanus. CNV undergoes a conformational change upon binding to the zoospore that is required for transmission, and specific polysaccharides on the zoospore surface have been implicated in binding. To better understand this transmission process, we have determined the atomic structure of CNV. As expected, being a member of the Tombusvirus genus, the core structure of CNV is highly similar to that of Tomato bushy stunt virus (TBSV), with major differences lying on the exposed loops. Also, as was seen with TBSV, CNV appears to have a calcium binding site between the subunits around the quasi-3-fold axes. However, unlike TBSV, there appears to be a novel zinc binding site within the ␤ annulus formed by the N termini of the three C subunits at the icosahedral 3-fold axes. Two of the mutations causing defective transmission map immediately around this zinc binding site. The other mutations causing defective transmission and particle formation are mapped onto the CNV structure, and it is likely that a number of the mutations affect zoospore transmission by affecting conformational transitions rather than directly affecting receptor binding. C ucumber necrosis virus (CNV) is a member of the genusTombusvirus and has a monopartite positive-sense RNA genome (1, 2). CNV is transmitted in nature via zoospores of the fungus Olpidium bornovanus (2-4). The type species of the Tombusvirus genus is Tomato bushy stunt virus (TBSV), and the structure of TBSV was the first virus structure determined by X-ray crystallography (5).These viruses have a Tϭ3 icosahedral protein shell with a diameter of ϳ300 Å formed from 180 identical coat protein (CP) subunits. The three conformationally distinct copies of the CPs, called A, B, and C, are shown in Fig. 1. The C subunits lie next to the icosahedral 2-fold axes, while the A and B subunits surround the 5-fold axes. Each capsid protein is comprised of three domains: the first ϳ60 residues at the N-terminal region (R), the shell (S) domain, and the protruding (P) domain (Fig. 2A). The first ϳ90 residues are disordered in the A and B subunits, while the first ϳ60 residues are disordered in the C subunit. Residues ϳ60 to 78 in the C subunit form a structure called the ␤ annulus that is thought to stabilize the capsid. The first ϳ60 residues at the N-terminal region interact with the RNA interior. Between this region (R) and the S domain are ϳ30 residues that act as a flexible connecting arm. The S domain is ϳ170 residues and forms a tight protein shell around the RNA genome. The final ϳ115 residues form the P domains, which combine with the adjacent subunit's P domains to form dimeric protrusions from the shell. The A subunits lie immediately adjacent to the icosahedral 5-fold axes, and their P domains interact with the P domains of adjacent B subunits to form 60 of the 90...

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Identification of Specific Cucumber Necrosis Virus Coat Protein Amino Acids Affecting Fungus Transmission and Zoospore Attachment

Cited by 49 publications

References 34 publications

Evidence that Binding of Cucumber Necrosis Virus to Vector Zoospores Involves Recognition of Oligosaccharides

Evidence that Binding of Cucumber Necrosis Virus to Vector Zoospores Involves Recognition of Oligosaccharides

A Conserved Capsid Protein Surface Domain of Cucumber Mosaic Virus Is Essential for Efficient Aphid Vector Transmission

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

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