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Comparative transcriptomic responses to compatible and incompatible plant-virus interactions that lead to cell death

ABSTRACT: Hypersensitive response-related programmed cell death (PCD) has been extensively analyzed in various plant–virus interactions. However, little is known about changes in gene expression associated with cell death caused by compatible viruses. The synergistic interaction of Potato virus X (PVX) with Plum pox virus (PPV) results in increased symptoms that lead to systemic necrosis (SN) in Nicotiana benthamiana. Here, we performed three transcriptome comparisons in response to i) a PVX recombinant virus expressing the helper component-proteinase (HC-Pro) gene from PPV that leads to SN, ii) a systemic incompatible interaction conferred by the Tobacco mosaic virus (TMV)-resistance gene N (SHR), and iii) the depletion of the PBE subunit of the proteasome that leads to PCD by virus induced gene silencing (VIGS Prot), at early and late stages of infection. Our analysis indicated that the SN response was clustered with SHR by the similarity of their overall gene expression profiles. However, the expression profiles of defence-related and hormone-responsive genes in response to SN were more closely related to the response to VIGS Prot than to that elicited by SHR. This suggests the potential contribution of proteasome dysfunction to the increase in pathogenicity observed in PVX-potyvirus infections

ORGANISM(S): Nicotiana tabacum Nicotiana benthamiana

PROVIDER: GSE34841 | GEO | 2012/02/02

SECONDARY ACCESSION(S): PRJNA150217

REPOSITORIES: GEO

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Project description:Hypersensitive response-related programmed cell death (PCD) has been extensively analyzed in various plant–virus interactions. However, little is known about changes in gene expression associated with cell death caused by compatible viruses. The synergistic interaction of Potato virus X (PVX) with Plum pox virus (PPV) results in increased symptoms that lead to systemic necrosis (SN) in Nicotiana benthamiana. Here, we performed three transcriptome comparisons in response to i) a PVX recombinant virus expressing the helper component-proteinase (HC-Pro) gene from PPV that leads to SN, ii) a systemic incompatible interaction conferred by the Tobacco mosaic virus (TMV)-resistance gene N (SHR), and iii) the depletion of the PBE subunit of the proteasome that leads to PCD by virus induced gene silencing (VIGS Prot), at early and late stages of infection. Our analysis indicated that the SN response was clustered with SHR by the similarity of their overall gene expression profiles. However, the expression profiles of defence-related and hormone-responsive genes in response to SN were more closely related to the response to VIGS Prot than to that elicited by SHR. This suggests the potential contribution of proteasome dysfunction to the increase in pathogenicity observed in PVX-potyvirus infections We compare the gene expression profiles of Nicotiana benthamiana plants infected with either necrosis-inducing viruses or non-necrosis-inducing viruses, as follow: PVX/HCWT-infected plants versus plants infected with a PVX recombinant virus expressing a PPV HC-Pro mutant (PVX/HCLH) that was unable to induce the SN response (SN comparison), at 7 and 11 days postinoculation (dpi), (ii) TRV:NbPBE-silenced plants versus plants infected with the TRV empty vector (VIGS Prot comparison), at 4 and 8 days after infiltration (dpa), and (iii) TMV-GFP-infected, N-transgenic plants versus wild-type plants infected with TMV-GFP (SHR comparison), at 24 and 72 hours after temperature shift (hts). Per time and treatment, three independent biological replicates were used to monitor differences in gene expression between treatments

Project description:The main goal of this study was to compare the differential efficiency of the antiviral activity triggered by externally delivered virus-specific and nonspecific dsRNAs in plants. RNAi mediated by virus-specific dsRNA is the main antiviral defense mechanism in plants, but nonspecific dsRNA-triggered responses have been documented to play a role in antiviral defense. Using PVX as a model, we have determined that co-inoculation with either virus-specific or nonspecific dsRNA reduced virus accumulation in both inoculated and systemic leaves although at different extent. While the administration of dsRNA specific for the targeted virus induced a potent RNAi-based antiviral response that resulted in highly effective control of viral disease, the degree of interference with PVX-GFP infection afforded by nonspecific dsRNA (PTI) was limited. To identify early biological processes and pathways associated with dsRNA-based immunity, we conducted a global transcriptome RNAseq assay from N. benthamiana leaves inoculated with four different treatments, i.e., dsGFP alone (dsG), PVX-GFP combined with dsGFP (dsG_VG), wild-type (Wt) PVX combined with dsGFP (dsG_V) and bacterial nucleic acid extracts not expressing dsRNA as a control (Ctr). KEGG analysis of differentially expressed genes showed a significant enrichment of terms related to plant-pathogen signaling pathways (KEGG terms Plant-pathogen interaction and MAPK signaling) in all the three treatments with dsRNA. Our results further indicate that the transcriptomic response triggered by dsRNA alone includes canonical immune pathways or genes known to be involved in defense responses, i.e., Ca+2 signaling, ethylene signaling, MAPK signaling, WRKY transcription factors, PR transcriptional factors, NBS-LRR resistance genes, EDS1, and LRR receptor-like kinases, many of which are typical of antimicrobial PTI . Moreover, the transcriptomic response to the homologous combination (dsGFP plus PVX-GFP) had a greater overrepresentation of genes involved in plant-pathogen signaling pathways than the heterologous combination (dsGFP plus Wt PVX), highlighting a quantitative difference between RNAi and PTI immune responses.

Project description:Many virus diseases of economic importance to agriculture result from mixtures of different pathogens invading the host at a given time. This contrasts with the relatively scarce studies available on the molecular events associated with virus-host interactions in mixed infections. In comparison to single infections, co-infection of Nicotiana benthamiana with Potato virus X (PVX) and Potato virus Y (PVY) resulted in increased systemic symptoms (synergism) that led to necrosis of the newly emerging leaves, and the plant death. A comparative transcriptional analysis was undertaken to identify quantitative and qualitative differences in gene expression during this synergistic infection, and to correlate these changes with the severe symptoms it caused. Global transcription profiles of doubly-infected leaves were compared with those from singly-infected leaves using gene ontology enrichment analysis and metabolic pathway annotator software. Functional gene categories altered by the double infection comprise suites of genes regulated coordinately, which are associated with chloroplast functions (down-regulated), protein synthesis and degradation (up-regulated), carbohydrate metabolism (up-regulated), and response to biotic stimulus and stress (up-regulated). The expression of reactive oxygen species-generating enzymes as well as several mitogen-activated protein kinases, were also significantly induced. Accordingly, synergistic infection induced a severe oxidative stress in N. benthamiana leaves, as judged by increases in lipid peroxidation, and by the generation of superoxide radicals in chloroplasts, which correlated with the misregulation of antioxidative genes in microarray data. Interestingly, expression of genes encoding oxylipin biosynthesis was uniquely up-regulated by the synergistic infection. Virus-induced gene silencing of alfa-dioxygenase1 delayed cell death during PVX-PVY infection. Using mock inoculated leaf tissue as a reference, we compare the gene expression profiles of Nicotiana benthamiana plants infected with one of two viruses, Potato virus X (PVX) or Potato virus Y (PVY), or the combination PVX plus PVY. 3 biological replicates per treatment were independently grown and haversted.

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Comparative transcriptomic responses to compatible and incompatible plant-virus interactions that lead to cell death

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