Suppressor activity of potyviral and cucumoviral infections in potyvirus-induced transgene silencing

Simón‐Mateo, Carmen; López‐Moya, Juan José; Guo, Hui; González, Elena; Garcı́a, Juan Antonio

doi:10.1099/vir.0.19263-0

Cited by 23 publications

(17 citation statements)

References 43 publications

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“…5C). These results are in agreement with a previous report showing that both TVMV and CMV infection reverted virus-induced silencing of N. benthamiana plants transformed with a PPV-derived transgene, but susceptibility to PPV was only restored in the CMV-infected transgenic plants, which suggested that TVMV infection could be eliciting an interpotyvirus cross-protection mechanism [31]. A possible contribution of wild type PPV or TVMV infection to the suppression of amplicon silencing in the 10.6 plants could have been masked by this uncharacterized cross-protection mechanism.…”

Section: Discussionsupporting

confidence: 93%

Constraints to virus infection in Nicotiana benthamiana plants transformed with a potyvirus amplicon

et al. 2010

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BackgroundPlant genomes have been transformed with full-length cDNA copies of viral genomes, giving rise to what has been called 'amplicon' systems, trying to combine the genetic stability of transgenic plants with the elevated replication rate of plant viruses. However, amplicons' performance has been very variable regardless of the virus on which they are based. This has boosted further interest in understanding the underlying mechanisms that cause this behavior differences, and in developing strategies to control amplicon expression.ResultsNicotiana benthamiana plants were transformed with an amplicon consisting of a full-length cDNA of the potyvirus Plum pox virus (PPV) genome modified to include a GFP reporter gene. Amplicon expression exhibited a great variability among different transgenic lines and even among different plants of the same line. Plants of the line 10.6 initially developed without signs of amplicon expression, but at different times some of them started to display sporadic infection foci in leaves approaching maturity. The infection progressed systemically, but at later times the infected plants recovered and returned to an amplicon-inactive state. The failure to detect virus-specific siRNAs in 10.6 plants before amplicon induction and after recovery suggested that a strong amplicon-specific RNA silencing is not established in these plants. However, the coexpression of extra viral silencing suppressors caused some amplicon activation, suggesting that a low level of RNA silencing could be contributing to maintain amplicon repression in the 10.6 plants. The resistance mechanisms that prevent amplicon-derived virus infection were also active against exogenous PPV introduced by mechanical inoculation or grafting, but did not affect other viruses. Amplicon-derived PPV was able to spread into wild type scions grafted in 10.6 rootstocks that did not display signs of amplicon expression, suggesting that resistance has little effect on virus movement.ConclusionsOur results suggest that amplicon-derived virus infection is limited in this particular transgenic line by a combination of factors, including the presumed low efficiency of the conversion from the transgene transcript to replicable viral RNA, and also by the activation of RNA silencing and other defensive responses of the plant, which are not completely neutralized by viral suppressors.

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Section: Discussionsupporting

confidence: 93%

Constraints to virus infection in Nicotiana benthamiana plants transformed with a potyvirus amplicon

et al. 2010

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“…This observation differs from the reports on the silencing-mediated resistance of transgenic N. benthamiana to Potato Virus A or Plum Pox Virus, which was overcome by preinfection with Potato virus Y (Savenkov & Valkonen, 2002) and CMV (Simon-Mateo et al, 2003), respectively.…”

Section: Discussioncontrasting

confidence: 84%

Transgenic cucumbers harboring the 54-kDa putative gene of Cucumber fruit mottle mosaic tobamovirus are highly resistant to viral infection and protect non-transgenic scions from soil infection

et al. 2005

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Cucumber fruit mottle mosaic tobamovirus (CFMMV) causes severe mosaic symptoms and yellow mottling on leaves and fruits and, occasionally, severe wilting of cucumber (Cucumis sativus L.) plants. No genetic source of resistance against this virus has been identified in cucumber. The gene coding for the putative 54-kDa replicase gene of CFMMV was cloned into an Agrobacterium tumefaciens binary vector, and transformation was performed on cotyledon explants of a parthenocarpic cucumber cultivar. R1 seedlings were screened for resistance to CFMMV by symptom expression, back inoculation on an alternative host and ELISA. From a total of 14 replicase-containing R1 lines, eight resistant lines were identified. Line 144--homozygous for the putative 54-kDa replicase gene--was immune to CFMMV infection by mechanical and graft inoculation, and to root infection following planting in CFMMV-infested soil. A substantial delay of symptom appearance was observed following infection by three additional cucurbit-infecting tobamoviruses. When used as a rootstock, line I44 protected susceptible cucumber scions from soil infection by CFMMV. This paper is the first report on protection of a susceptible cultivar against a soil-borne viral pathogen, by grafting onto a transgenic rootstock.

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“…This suppressor could reduce, but not eliminate, siRNA in the local and systemic RNA silencing suppression assays (Figures 1-3), suggesting that Pns11 functions similarly to CMV 2b [40] and to turnip yellow mosaic virus p69 [23] , but not to PVY HC-Pro [41] , by interfering with initial stages of RNA silencing. Whether Pns11 could suppress dsRNAinduced RNA silencing was still unknown.…”

Section: Discussionmentioning

confidence: 91%

Suppressor of RNA silencing encoded by Rice gall dwarf virus genome segment 11

et al. 2008

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Rice gall dwarf virus (RGDV) is an important rice pathogen in China andSoutheast Asia. However, little is known about the molecular mechanisms of RGDV interactions with plant cells. Here, we have identified an RGDV protein, Pns11, which acts as a suppressor of RNA silencing in coinfiltration assays with the reporter, green fluorescent protein (GFP) in transgenic Nicotiana benthamiana line 16c carrying GFP. Pns11 suppressed local and systemic silencing induced by sense RNA. The spread of mobile RNA silencing signals was blocked or inactivated by Pns11. Expression of Pns11 also enhanced Potato virus X pathogenicity in N. benthamiana. This suppressor could reduce, but not eliminate, siRNA in the local and systemic RNA silencing suppression assays, suggesting that Pns11 functions by interfering with initial stages of RNA silencing. Rice gall dwarf virus (RGDV), RNA silencing, suppressorRNA silencing is an evolutionarily conserved surveillance system that occurs in a broad range of eukaryotic organisms including quelling in fungi, RNA interference (RNAi) in animals, and post-transcriptional gene silencing (PTGS) in plants [1][2][3] . The process is initially triggered by dsRNA, which can be introduced experimentally or arise from endogenous transposons, replicating RNA viruses, or the transcription of transgenes. The dsRNA trigger is cleaved by a ribonuclease III (RNAse III)-like enzyme termed Dicer into 21-26 nucleotide duplexes termed short-interfering RNAs (siRNAs) [4][5][6] .

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Suppressor activity of potyviral and cucumoviral infections in potyvirus-induced transgene silencing

Cited by 23 publications

References 43 publications

Constraints to virus infection in Nicotiana benthamiana plants transformed with a potyvirus amplicon

Constraints to virus infection in Nicotiana benthamiana plants transformed with a potyvirus amplicon

Transgenic cucumbers harboring the 54-kDa putative gene of Cucumber fruit mottle mosaic tobamovirus are highly resistant to viral infection and protect non-transgenic scions from soil infection

Suppressor of RNA silencing encoded by Rice gall dwarf virus genome segment 11

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