Transgenic <i>Arabidopsis</i> Lines Expressing Gene VI from Cauliflower Mosaic Virus Variants Exhibit a Range of Symptom-Like Phenotypes and Accumulate Inclusion Bodies

Cecchini, Edi; Gong, Zhen-Hui; Geri, C.; Covey, Simon N.; Milner, Joel J.

doi:10.1094/mpmi.1997.10.9.1094

Cited by 56 publications

(75 citation statements)

References 33 publications

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“…Transgene-mediated expression of P6 in Arabidopsis results in a chlorotic dwarf phenotype and alterations in leaf morphology (Zijlstra et al, 1996;Cecchini et al, 1997) reminiscent of those induced by silencing suppressors, e.g. tobacco etch potyvirus HC-Pro (Kasschau et al, 2003).…”

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confidence: 99%

“…We crossed GxA with two independent transgenic lines A7 and B6 that constitutively express high levels of P6 from CaMV isolate Cabb B-JI under the control of a 35S promoter (Cecchini et al, 1997). To avoid the complication of three segregating transgenes, experiments were carried out on F 1 progeny.…”

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confidence: 99%

“…Suppression of silencing provides a plausible explanation for the role of P6 in host pathogenicity and for the altered leaf morphology and symptom-like phenotype that result from transgene-mediated expression (Cecchini et al, 1997;Yu et al, 2003). Virus-encoded silencing suppressors induce developmental aberrations when expressed from transgenes (Voinnet, 2005;Moissiard & Voinnet, 2004), and these have been attributed to alterations in the activity of miRNA pathways (Kasschau et al, 2003;Lewsey et al, 2007).…”

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confidence: 99%

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Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

Love

Laird

Holt

et al. 2007

Journal of General Virology

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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 ...

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confidence: 99%

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Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

Love

Laird

Holt

et al. 2007

Journal of General Virology

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“…Consequently, the evolution of viral genomes depends on both point mutations and genomic recombinations (Escriu et al, 2007). As previously demonstrated on different types of virus, a single point mutation within the genome sequence (coding or non-coding regions) can induce modification(s) of the biological properties of the corresponding viral genotype (Rigden et al, 1994;Zhang et al, 1994;Kong et al, 1995;Van der Vossen et al, 1996;Cecchini et al, 1997;Hirata et al, 2003). The maintenance and spread of any new genotype within a viral quasispecies depends on its fitness, i.e.…”

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The acquisition of molecular determinants involved in potato virus Y necrosis capacity leads to fitness reduction in tobacco plants

Rolland

Kerlan

Jacquot

2009

Journal of General Virology

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The prevalence of necrotic potato virus Y (PVY) in natural populations could reflect increased fitness of necrotic isolates. In this paper, the effects of the acquisition of molecular determinants (A/G 2213 and A/C 2271 ) involved in necrosis capacity on both the number of progeny produced and the competitiveness of PVY were characterized. The relationship between necrosis and fitness was tested using (i) Nicotiana tabacum cv. competitiveness. In contrast, nucleotides involved in necrotic properties were associated with decreased fitness. Finally, in the host that did not respond to infection with necrosis, the benefit associated with the PVY N -605 genetic background was higher than the cost associated with the acquisition of molecular determinants involved in necrosis capacity. The opposite result was obtained in the host responding to the infection with necrosis. These results indicate that the emergence of necrotic isolates from a non-necrotic population is unlikely in tobacco.

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“…Third, P6 is an important pathogenicity determinant. P6 functions as an avirulence determinant in some solanaceous and cruciferous species (Daubert et al, 1984;Schoelz et al, 1986;Hapiak et al, 2008) and is a chlorosis symptom determinant in susceptible hosts (Daubert et al, 1984;Baughman et al, 1988;Goldberg et al, 1991;Cecchini et al, 1997). Finally, P6 has the capacity to compromise host defenses, as it is a suppressor of RNA silencing and cell death (Love et al, 2007;Haas et al, 2008), and it modulates signaling by salicylic acid, jasmonic acid, ethylene, and auxin (Geri et al, 2004;Love et al, 2012;Laird et al, 2013).…”

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Association of the P6 Protein of Cauliflower mosaic virus with Plasmodesmata and Plasmodesmal Proteins

et al. 2014

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The P6 protein of Cauliflower mosaic virus (CaMV) is responsible for the formation of inclusion bodies (IBs), which are the sites for viral gene expression, replication, and virion assembly. Moreover, recent evidence indicates that ectopically expressed P6 inclusion-like bodies (I-LBs) move in association with actin microfilaments. Because CaMV virions accumulate preferentially in P6 IBs, we hypothesized that P6 IBs have a role in delivering CaMV virions to the plasmodesmata. We have determined that the P6 protein interacts with a C2 calcium-dependent membrane-targeting protein (designated Arabidopsis [Arabidopsis thaliana] Soybean Response to Cold [AtSRC2.2]) in a yeast (Saccharomyces cerevisiae) two-hybrid screen and have confirmed this interaction through coimmunoprecipitation and colocalization assays in the CaMV host Nicotiana benthamiana. An AtSRC2.2 protein fused to red fluorescent protein (RFP) was localized to the plasma membrane and specifically associated with plasmodesmata. The AtSRC2.2-RFP fusion also colocalized with two proteins previously shown to associate with plasmodesmata: the host protein Plasmodesmata-Localized Protein1 (PDLP1) and the CaMV movement protein (MP). Because P6 I-LBs colocalized with AtSRC2.2 and the P6 protein had previously been shown to interact with CaMV MP, we investigated whether P6 I-LBs might also be associated with plasmodesmata. We examined the colocalization of P6-RFP I-LBs with PDLP1-green fluorescent protein (GFP) and aniline blue (a stain for callose normally observed at plasmodesmata) and found that P6-RFP I-LBs were associated with each of these markers. Furthermore, P6-RFP coimmunoprecipitated with PDLP1-GFP. Our evidence that a portion of P6-GFP I-LBs associate with AtSRC2.2 and PDLP1 at plasmodesmata supports a model in which P6 IBs function to transfer CaMV virions directly to MP at the plasmodesmata.Through the years, numerous studies have focused on the characterization of viral replication sites within the cell, as well as how plant virus movement proteins (MPs) modify the plasmodesmata to facilitate cell-tocell movement (for review, see Benitez-Alfonso et al.,

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Transgenic Arabidopsis Lines Expressing Gene VI from Cauliflower Mosaic Virus Variants Exhibit a Range of Symptom-Like Phenotypes and Accumulate Inclusion Bodies

Cited by 56 publications

References 33 publications

Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

The acquisition of molecular determinants involved in potato virus Y necrosis capacity leads to fitness reduction in tobacco plants

Association of the P6 Protein of Cauliflower mosaic virus with Plasmodesmata and Plasmodesmal Proteins

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