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Impact of Exogenous Application of Potato Virus Y-Specific dsRNA on RNA Interference, Pattern-Triggered Immunity and Poly(ADP-ribose) Metabolism.

ABSTRACT: In this work we developed and exploited a spray-induced gene silencing (SIGS)-based approach to deliver double-stranded RNA (dsRNA), which was found to protect potato against potato virus Y (PVY) infection. Given that dsRNA can act as a defence-inducing signal that can trigger sequence-specific RNA interference (RNAi) and non-specific pattern-triggered immunity (PTI), we suspected that these two pathways may be invoked via exogeneous application of dsRNA, which may account for the alterations in PVY susceptibility in dsRNA-treated potato plants. Therefore, we tested the impact of exogenously applied PVY-derived dsRNA on both these layers of defence (RNAi and PTI) and explored its effect on accumulation of a homologous virus (PVY) and an unrelated virus (potato virus X, PVX). Here, we show that application of PVY dsRNA in potato plants induced accumulation of both small interfering RNAs (siRNAs), a hallmark of RNAi, and some PTI-related gene transcripts such as WRKY29 (WRKY transcription factor 29; molecular marker of PTI), RbohD (respiratory burst oxidase homolog D), EDS5 (enhanced disease susceptibility 5), SERK3 (somatic embryogenesis receptor kinase 3) encoding brassinosteroid-insensitive 1-associated receptor kinase 1 (BAK1), and PR-1b (pathogenesis-related gene 1b). With respect to virus infections, PVY dsRNA suppressed only PVY replication but did not exhibit any effect on PVX infection in spite of the induction of PTI-like effects in the presence of PVX. Given that RNAi-mediated antiviral immunity acts as the major virus resistance mechanism in plants, it can be suggested that dsRNA-based PTI alone may not be strong enough to suppress virus infection. In addition to RNAi- and PTI-inducing activities, we also showed that PVY-specific dsRNA is able to upregulate production of a key enzyme involved in poly(ADP-ribose) metabolism, namely poly(ADP-ribose) glycohydrolase (PARG), which is regarded as a positive regulator of biotic stress responses. These findings offer insights for future development of innovative approaches which could integrate dsRNA-induced RNAi, PTI and modulation of poly(ADP-ribose) metabolism in a co-ordinated manner, to ensure a high level of crop protection.

SUBMITTER: Samarskaya VO

PROVIDER: S-EPMC9317112 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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:BackgroundInitiation, amplitude, duration and termination of transforming growth factor ? (TGF?) signaling via Smad proteins is regulated by post-translational modifications, including phosphorylation, ubiquitination and acetylation. We previously reported that ADP-ribosylation of Smads by poly(ADP-ribose) polymerase 1 (PARP-1) negatively influences Smad-mediated transcription. PARP-1 is known to functionally interact with PARP-2 in the nucleus and the enzyme poly(ADP-ribose) glycohydrolase (PARG) can remove poly(ADP-ribose) chains from target proteins. Here we aimed at analyzing possible cooperation between PARP-1, PARP-2 and PARG in regulation of TGF? signaling.MethodsA robust cell model of TGF? signaling, i.e. human HaCaT keratinocytes, was used. Endogenous Smad3 ADP-ribosylation and protein complexes between Smads and PARPs were studied using proximity ligation assays and co-immunoprecipitation assays, which were complemented by in vitro ADP-ribosylation assays using recombinant proteins. Real-time RT-PCR analysis of mRNA levels and promoter-reporter assays provided quantitative analysis of gene expression in response to TGF? stimulation and after genetic perturbations of PARP-1/-2 and PARG based on RNA interference.ResultsTGF? signaling rapidly induces nuclear ADP-ribosylation of Smad3 that coincides with a relative enhancement of nuclear complexes of Smads with PARP-1 and PARP-2. Inversely, PARG interacts with Smads and can de-ADP-ribosylate Smad3 in vitro. PARP-1 and PARP-2 also form complexes with each other, and Smads interact and activate auto-ADP-ribosylation of both PARP-1 and PARP-2. PARP-2, similar to PARP-1, negatively regulates specific TGF? target genes (fibronectin, Smad7) and Smad transcriptional responses, and PARG positively regulates these genes. Accordingly, inhibition of TGF?-mediated transcription caused by silencing endogenous PARG expression could be relieved after simultaneous depletion of PARP-1.ConclusionNuclear Smad function is negatively regulated by PARP-1 that is assisted by PARP-2 and positively regulated by PARG during the course of TGF? signaling.

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Impact of Exogenous Application of Potato Virus Y-Specific dsRNA on RNA Interference, Pattern-Triggered Immunity and Poly(ADP-ribose) Metabolism.

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