Symptom recovery in virus-infected plants: Revisiting the role of RNA silencing mechanisms

Ghoshal, Basudev; Sanfaçon, Hélène

doi:10.1016/j.virol.2015.01.008

Cited by 145 publications

(127 citation statements)

References 165 publications

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“…Virus-infected plants show a range of symptoms depending on the pathogen; these symptoms often include leaf yellowing, leaf distortion, leaf curling, and other growth distortions like stunting of the whole plant, abnormalities in flower or fruit formation, etc. (Ghoshal and Sanfacon, 2015). Plant viruses are classified into six major groups based on their genomes: double-stranded DNA (dsDNA) viruses, single-stranded DNA (ssDNA) viruses, reverse-transcribing viruses, double-stranded RNA (dsRNA) viruses, negative sense single-stranded RNA (ssRNA-) viruses, and positive sense single-stranded RNA (ssRNA+) viruses (Roossinck, 2011; Roossinck et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Engineering Plant Immunity: Using CRISPR/Cas9 to Generate Virus Resistance

et al. 2016

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Plant viruses infect many economically important crops, including wheat, cotton, maize, cassava, and other vegetables. These viruses pose a serious threat to agriculture worldwide, as decreases in cropland area per capita may cause production to fall short of that required to feed the increasing world population. Under these circumstances, conventional strategies can fail to control rapidly evolving and emerging plant viruses. Genome-engineering strategies have recently emerged as promising tools to introduce desirable traits in many eukaryotic species, including plants. Among these genome engineering technologies, the CRISPR (clustered regularly interspaced palindromic repeats)/CRISPR-associated 9 (CRISPR/Cas9) system has received special interest because of its simplicity, efficiency, and reproducibility. Recent studies have used CRISPR/Cas9 to engineer virus resistance in plants, either by directly targeting and cleaving the viral genome, or by modifying the host plant genome to introduce viral immunity. Here, we briefly describe the biology of the CRISPR/Cas9 system and plant viruses, and how different genome engineering technologies have been used to target these viruses. We further describe the main findings from recent studies of CRISPR/Cas9-mediated viral interference and discuss how these findings can be applied to improve global agriculture. We conclude by pinpointing the gaps in our knowledge and the outstanding questions regarding CRISPR/Cas9-mediated viral immunity.

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Section: Introductionmentioning

confidence: 99%

Engineering Plant Immunity: Using CRISPR/Cas9 to Generate Virus Resistance

et al. 2016

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“…The natural outcome of this plantvirus interaction (host recovery) is the emergence of new asymptomatic leaves after a typical symptomatic infection. Host recovery is generally accompanied with reduced virus titers and a sequence-specific resistance to a secondary infection, and it has been linked with the induction of an antiviral RNA-silencing process (21,22).…”

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confidence: 99%

Two Populations of Viral Minichromosomes Are Present in a Geminivirus-Infected Plant Showing Symptom Remission (Recovery)

Ceniceros-Ojeda

Rodríguez-Negrete

Rivera-Bustamante

2016

J Virol

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Geminiviruses are important plant pathogens characterized by circular, single-stranded DNA (ssDNA) genomes. However, in the nuclei of infected cells, viral double-stranded DNA (dsDNA) associates with host histones to form a minichromosome. In phloem-limited geminiviruses, the characterization of viral minichromosomes is hindered by the low concentration of recovered complexes due to the small number of infected cells. Nevertheless, geminiviruses are both inducers and targets of the host posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) machinery. We have previously characterized a "recovery" phenomenon observed in pepper plants infected with pepper golden mosaic virus (PepGMV) that is associated with a reduction of viral DNA and RNA levels, the presence of virus-related siRNAs, and an increase in the levels of viral DNA methylation. Initial micrococcal nuclease-based assays pinpointed the presence of different viral chromatin complexes in symptomatic and recovered tissues. Using the pepper-PepGMV system, we developed a methodology to obtain a viral minichromosome-enriched fraction that does not disturb the basic chromatin structural integrity, as evaluated by the detection of core histones. Using this procedure, we have further characterized two populations of viral minichromosomes in PepGMV-infected plants. After further purification using sucrose gradient sedimentation, we also observed that minichromosomes isolated from symptomatic tissue showed a relaxed conformation (based on their sedimentation rate), are associated with a chromatin activation marker (H3K4me3), and present a low level of DNA methylation. The minichromosome population obtained from recovered tissue, on the other hand, sedimented as a compact structure, is associated with a chromatin-repressive marker (H3K9me2), and presents a high level of DNA methylation. IMPORTANCEViral minichromosomes have been reported in several animal and plant models. However, in the case of geminiviruses, there has been some recent discussion about the importance of this structure and the significance of the epigenetic modifications that it can undergo during the infective cycle. Major problems in this type of studies are the low concentration of these complexes in an infected plant and the asynchronicity of infected cells along the process; therefore, the complexes isolated in a given moment usually represent a mixture of cells at different infection stages. The recovery process observed in PepGMV-infected plants and the isolation procedure described here provide two distinct populations of minichromosomes that will allow a more precise characterization of the modifications of viral DNA and its host proteins associated along the infective cycle. This structure could be also an interesting model to study several processes involving plant chromatin. G eminiviruses are important plant pathogens consisting of circular, single-stranded DNA (ssDNA) genomes ranging from 2.7 to 5.2 kb packed into 1 or 2 icosahedral twine-shaped part...

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“…RNA silencing also represents a well-documented antiviral mechanism in plants (Ding, 2010; Pumplin and Voinnet, 2013; Csorba et al , 2015; Ghoshal and Sanfaçon, 2015). Viral RNAs can be addressed for degradation via the endonucleolytic activity of argonaute (AGO), the catalytic component of the RNA-induced silencing complex (RISC; Mallory and Vaucheret, 2010).…”

Section: Introductionmentioning

confidence: 99%

Translational control in plant antiviral immunity

et al. 2017

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Due to the limited coding capacity of viral genomes, plant viruses depend extensively on the host cell machinery to support the viral life cycle and, thereby, interact with a large number of host proteins during infection. Within this context, as plant viruses do not harbor translation-required components, they have developed several strategies to subvert the host protein synthesis machinery to produce rapidly and efficiently the viral proteins. As a countermeasure against infection, plants have evolved defense mechanisms that impair viral infections. Among them, the host-mediated translational suppression has been characterized as an efficient mean to restrict infection. To specifically suppress translation of viral mRNAs, plants can deploy susceptible recessive resistance genes, which encode translation initiation factors from the eIF4E and eIF4G family and are required for viral mRNA translation and multiplication. Additionally, recent evidence has demonstrated that, alternatively to the cleavage of viral RNA targets, host cells can suppress viral protein translation to silence viral RNA. Finally, a novel strategy of plant antiviral defense based on suppression of host global translation, which is mediated by the transmembrane immune receptor NIK1 (nuclear shuttle protein (NSP)-Interacting Kinase1), is discussed in this review.

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Symptom recovery in virus-infected plants: Revisiting the role of RNA silencing mechanisms

Cited by 145 publications

References 165 publications

Engineering Plant Immunity: Using CRISPR/Cas9 to Generate Virus Resistance

Engineering Plant Immunity: Using CRISPR/Cas9 to Generate Virus Resistance

Two Populations of Viral Minichromosomes Are Present in a Geminivirus-Infected Plant Showing Symptom Remission (Recovery)

Translational control in plant antiviral immunity

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