Dissection of Cauliflower Mosaic Virus Transactivator/Viroplasmin Reveals Distinct Essential Functions in Basic Virus Replication

Kobayashi, Kappei; Höhn, Thomas

doi:10.1128/jvi.77.15.8577-8583.2003

Cited by 36 publications

(41 citation statements)

References 36 publications

(34 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3c). In the previous study in turnip protoplasts, TavD2 and TavD6 accumulated to levels similar to the wild-type Tav, while the TavD8 protein was not detected, most likely due to reduced stability of the mutant protein (Kobayashi and Hohn 2003). The difference in expression levels in the transgenic tobacco lines of the mutant proteins could be attributed to the different location of the transgenes in the tobacco chromosome.…”

Section: Mutational Analysis For the Chlorosis-inducing Function Of Tavmentioning

confidence: 89%

“…To identify the domain(s) involved in Tav-induced chlorosis in transgenic tobacco plants, we generated transgenic tobacco lines similar to iTav-tobacco lines, but with an in-frame deletion in different parts: TavD2 lacking amino acid residues (AA) 41-73; TavD6 lacking AA 167-200, and TavD8 lacking AA 246-298 ( Fig. 3b) (Kobayashi and Hohn 2003). When the iTav-tobacco lines and its deletion mutant lines were treated with Dex and analyzed for Tav protein expression, protein bands of the expected size were detected with varying intensities within different lines (Fig.…”

Section: Mutational Analysis For the Chlorosis-inducing Function Of Tavmentioning

confidence: 99%

“…In some experiments, Dex (50 lM in 0.01 % v/v Tween-20) was painted onto the leaf surface with a brush. Transgenic plants harboring deletion mutants of Tav (Kobayashi and Hohn 2003) under the control of a Dex-inducible promoter were generated and grown the same as those harboring wild-type Tav (Waliullah et al 2014). Plants were sprayed with 1 mM SA (Nacalai tesque) using a hand-held mister.…”

Section: Plants and Chemicalsmentioning

confidence: 99%

See 2 more Smart Citations

Cauliflower mosaic virus Tav protein induces leaf chlorosis in transgenic tobacco through a host response to virulence function of Tav

et al. 2015

Self Cite

View full text Add to dashboard Cite

To study the precise mechanisms underlying the chlorosis caused by plant viruses, we previously established a synchronous experimental system using transgenic plants expressing Cauliflower mosaic virus multifunctional protein, Tav (transactivator/viroplasmin), under the control of an artificially inducible promoter. Shortly after the induction of Tav expression, pathogenesis-related protein (PR) 1a gene expression is upregulated in the transgenic tobacco lines, which show visible chlorosis within a week. The present study showed that the expression of Tav also induces some salicylic acid (SA)-and ethylene-responsive PR genes. In contrast to transiently expressed Tav, which suppressed Agrobacterium-induced and SA-induced PR1a expression, the artificial induction of Tav from the transgene did not affect SAinduced PR1a expression, rather it alone induced PR1a expression. In a deletion analysis, chlorosis and PR1a induction function in transgenic tobacco were mapped to a region in Tav that had been shown to have a role in pathogenesis in a susceptible host, elicitation of the hypersensitive response in a resistant host, suppression of RNA silencing, and the suppression of Tomato bushy stunt virus P19-mediated cell death in tobacco. The results suggest that Tav-induced chlorosis results from a host response, which accompanies PR1a induction, to pathogenic function of Tav.

show abstract

Section: Mutational Analysis For the Chlorosis-inducing Function Of Tavmentioning

confidence: 89%

Section: Mutational Analysis For the Chlorosis-inducing Function Of Tavmentioning

confidence: 99%

Section: Plants and Chemicalsmentioning

confidence: 99%

See 1 more Smart Citation

Cauliflower mosaic virus Tav protein induces leaf chlorosis in transgenic tobacco through a host response to virulence function of Tav

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Concerning the involvement of the other residues of the I1 invariant sequence, further investigations are necessary to definitively answer this question. Interestingly, the NES is part of the a-helix that is involved in P6 self-assembly and this fact might explain why deletion of the first 90 nucleotides of the CaMV ORF VI abolishes systemic infection and significantly reduces the replication of the genome in single cells (Kobayashi and Hohn, 2003). The overlap between domains involved in P6 export and self-assembly also raises the question of how these two activities are regulated during the viral cycle.…”

Section: Discussionmentioning

confidence: 99%

The Open Reading Frame VI Product ofCauliflower mosaic virusIs a Nucleocytoplasmic Protein: Its N Terminus Mediates Its Nuclear Export and Formation of Electron-Dense Viroplasms

et al. 2005

Self Cite

View full text Add to dashboard Cite

The Cauliflower mosaic virus (CaMV) open reading frame VI product (P6) is essential for the viral infection cycle. It controls translation reinitiation of the viral polycistronic RNAs and forms cytoplasmic inclusion bodies (viroplasms) where virus replication and assembly occur. In this study, the mechanism involved in viroplasm formation was investigated by in vitro and in vivo experiments. Far protein gel blot assays using a collection of P6 deletion mutants demonstrated that the N-terminal a-helix of P6 mediates interaction between P6 molecules. Transient expression in tobacco (Nicotiana tabacum) BY-2 cells of full-length P6 and P6 mutants fused to enhanced green fluorescent protein revealed that viroplasms are formed at the periphery of the nucleus and that the N-terminal domain of P6 is an important determinant in this process. Finally, this study led to the unexpected finding that P6 is a nucleocytoplasmic shuttle protein and that its nuclear export is mediated by a Leu-rich sequence that is part of the a-helix domain implicated in viroplasm formation. The discovery that P6 can localize to the nucleus opens new prospects for understanding yet unknown roles of this viral protein in the course of the CaMV infection cycle.

show abstract

“…This was counter-intuitive given the potential role of P6 as a silencing suppressor. However, P6 is also essential for correct translation of the 35S RNA (Haas et al, 2002; Bureau et al, 2004), and translational transactivation and pathogenicity have been reported to map to different domains of the protein (Kobayashi & Hohn, 2003). Possibly reduced virus load might be a consequence of aberrant regulation of translation of 35S RNA in P6-transgenic plants.…”

mentioning

confidence: 99%

Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

Love

Laird

Holt

et al. 2007

Journal of General Virology

View full text Add to dashboard Cite

We infected a transgenic Arabidopsis line (GxA), containing an amplicon-silenced 35S : : GFP transgene, with cauliflower mosaic virus (CaMV), a plant pararetrovirus with a DNA genome. Systemically infected leaves showed strong GFP fluorescence and amplicon transcripts were detectable in Northern blots, indicating that silencing of GFP had been suppressed during CaMV-infection. Transgenic Arabidopsis lines expressing CaMV protein P6, the major genetic determinant of symptom severity, were crossed with GxA. Progeny showed strong GFP fluorescence throughout and amplicon transcripts were detectable in Northern blots, indicating that P6 was suppressing local and systemic silencing. However, levels of 21 nt siRNAs derived from the GFP transgene were not reduced. In CaMV-infected plants, the P6 transgene did not reduce levels of CaMV leader-derived 21 and 24 nt siRNAs relative to levels of CaMV 35S RNA. These results demonstrate that CaMV can efficiently suppress silencing of a GFP transgene, and that P6 acts as a silencing suppressor.RNA silencing is an important defence mechanism against virus infection, and many plant viruses encode countersilencing proteins (Voinnet, 2001;Moissiard & Voinnet, 2004). The trigger for silencing is the presence of doublestranded (ds) RNA. For viruses with single-stranded RNA genomes, dsRNAs comprise an essential replication intermediate. dsRNAs are not obligate replication intermediates for viruses with DNA genomes but may nevertheless accumulate during infection (Blevins et al., 2006). Several geminiviruses undergo silencing, and several also encode silencing suppressors (Bisaro, 2006;Cui et al., 2005;Trinks et al., 2005). Cauliflower mosaic virus (CaMV), the type member of the family Caulimoviridae, is a pararetrovirus with an 8 kbp dsDNA genome and replicates by reverse transcription (Haas et al., 2002). In Brassica napus, CaMV undergoes silencing (Al Kaff et al., 1998), and CaMVinfected Arabidopsis accumulate siRNAs that are derived mainly from the viral 35S RNA leader (Moissiard & Voinnet, 2006;Blevins et al., 2006).To test whether CaMV is also capable of suppressing silencing, we infected a transgenic Arabidopsis line in which expression of GFP is silenced (Dalmay et al., 2000). GxA (obtained from Professor D. C. Baulcombe, Sainsbury Laboratory, Norwich, UK) contains both a 35S : : GFP transgene and one expressing a potato virus X (PVX) amplicon from a phloem-specific promoter. The amplicon, which is silenced, contains GFP sequences and these cosuppress the 35S : : GFP transgene. GxA allows analysis of both local silencing in the vascular tissue (where the amplicon is expressed), and systemic movement of the silencing signal into the remaining leaf tissue (Dalmay et al., 2000).Groups of approximately ten plants were inoculated with CaMV, either manually at the two-leaf stage (Cecchini et al., 1998), or by particle bombardment at the eight-leaf stage (Love et al., 2007). Inoculated plants began to show typical systemic symptoms of infection (distortion and stunting of the central ...

show abstract

Dissection of Cauliflower Mosaic Virus Transactivator/Viroplasmin Reveals Distinct Essential Functions in Basic Virus Replication

Cited by 36 publications

References 36 publications

Cauliflower mosaic virus Tav protein induces leaf chlorosis in transgenic tobacco through a host response to virulence function of Tav

Cauliflower mosaic virus Tav protein induces leaf chlorosis in transgenic tobacco through a host response to virulence function of Tav

The Open Reading Frame VI Product ofCauliflower mosaic virusIs a Nucleocytoplasmic Protein: Its N Terminus Mediates Its Nuclear Export and Formation of Electron-Dense Viroplasms

Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

Contact Info

Product

Resources

About