The good viruses: viral mutualistic symbioses. Nat Rev Microbiol 9:99-108

Samuel Roberts Noble Foundation, Plant Biology Division, Ardmore, Oklahoma 73401, USA.
Nature Reviews Microbiology (Impact Factor: 23.57). 02/2011; 9(2):99-108. DOI: 10.1038/nrmicro2491
Source: PubMed


Although viruses are most often studied as pathogens, many are beneficial to their hosts, providing essential functions in some cases and conditionally beneficial functions in others. Beneficial viruses have been discovered in many different hosts, including bacteria, insects, plants, fungi and animals. How these beneficial interactions evolve is still a mystery in many cases but, as discussed in this Review, the mechanisms of these interactions are beginning to be understood in more detail.

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    • "Studies of plant–virus interactions in wild ecosystems are still limited (Cooper & Jones, 2006; Alexander et al., 2014; Roossinck & Garc ıa-Arenal, 2015) and although there are well documented examples of viruses causing obvious diseases in wild plants, affecting plant population sizes and plant ecosystem composition (Malmstrom et al., 2005; Power et al., 2011; R ua et al., 2011; Rodelo-Urrego et al., 2013; Prendeville et al., 2014), most virus infections in wild plants are asymptomatic (Pag an et al., 2010; Prendeville et al., 2012; Roossinck, 2012; Stobbe & Roossinck, 2014). Indeed, it has been proposed that plant viruses would most often be commensals, or even mutualists of plants, and that pathogenic virus infections may be, at least in part, a result of the specific conditions of agricultural ecosystems (Gibbs, 1980; Wren et al., 2006; Xu et al., 2008; Roossinck, 2011). Thus, the pathogenicity of viruses for plants is an ongoing subject of debate, and it is important to understand under which conditions viruses will be virulent parasites of plants. "
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    ABSTRACT: It has been hypothesized that plant-virus interactions vary between antagonism and conditional mutualism according to environmental conditions. This hypothesis is based on scant experimental evidence, and to test it we examined the effect of abiotic factors on the Arabidopsis thaliana-Cucumber mosaic virus (CMV) interaction. Four Arabidopsis genotypes clustering into two allometric groups were grown under six environments defined by three temperature and two light-intensity conditions. Plants were either CMV-infected or mock-inoculated, and the effects of environment and infection on temporal and resource allocation life-history traits were quantified. Life-history traits significantly differed between allometric groups over all environments, with group 1 plants tolerating abiotic stress better than those of group 2. The effect of CMV infection on host fitness (virulence) differed between genotypes, being lower in group 1 genotypes. Tolerance to abiotic stress and to infection was similarly achieved through life-history trait responses, which resulted in resource reallocation from growth to reproduction. Effects of infection varied according to plant genotype and environment from detrimental to beneficial for host fitness. These results are highly relevant and demonstrate that plant viruses can be pleiotropic parasites along the antagonism-mutualism continuum, which should be considered in analyses of the evolution of plant-virus interactions.
    New Phytologist 09/2015; DOI:10.1111/nph.13631 · 7.67 Impact Factor
    • "This observation is consistent with the hypothesis that disease is an evolutionarily disadvantageous state for both viruses and their hosts and generally only occurs as a result of maladapted interactions within newly formed parasitic relationships (Bao and Roossinck 2013). Beyond disease and parasitism, metagenomics may reveal a multitude of mutualistic relationships between viruses and plants (Roossinck 2011, 2013). Metagenomic-oriented approaches are ideally suited to test such hypotheses. "
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    ABSTRACT: In recent years plant viruses have been detected from many environments, including domestic and wild plants and interfaces between these systems-aquatic sources, feces of various animals, and insects. A variety of methods have been employed to study plant virus biodiversity, including enrichment for virus-like particles or virus-specific RNA or DNA, or the extraction of total nucleic acids, followed by next-generation deep sequencing and bioinformatic analyses. All of the methods have some shortcomings, but taken together these studies reveal our surprising lack of knowledge about plant viruses and point to the need for more comprehensive studies. In addition, many new viruses have been discovered, with most virus infections in wild plants appearing asymptomatic, suggesting that virus disease may be a byproduct of domestication. For plant pathologists these studies are providing useful tools to detect viruses, and perhaps to predict future problems that could threaten cultivated plants.
    Phytopathology 06/2015; 105(6):PHYTO12140356RVW. DOI:10.1094/PHYTO-12-14-0356-RVW · 3.12 Impact Factor
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    • "Viruses play important roles as pathogens and mutualists in many, if not all, forms of cellular life (Munn, 2006; Suttle, 2007; Roossinck, 2011) and undoubtedly have important but currently unknown functions in the coral stress response, coral disease, and the adaptive potential of the coral holobiont with respect to climate change (van Oppen et al., 2009; Thurber and Correa, 2011). Metagenomic characterization of coral-associated viruses is a first step towards elucidating these roles. "
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    ABSTRACT: Reef-building corals form close associations with organisms from all three domains of life and therefore have many potential viral hosts. Yet, knowledge of viral communities associated with corals is barely explored. This complexity presents a number of challenges in terms of the metagenomic assessments of coral viral communities, and requires specialised methods for purification and amplification of viral nucleic acids, as well as virome annotation. In this mini-review, we conduct a meta-analysis of the limited number of existing coral virome studies, as well as available coral transcriptome and metagenome data, to identify trends and potential complications inherent in different methods. The analysis shows that the method used for viral nucleic acid isolation drastically affects the observed viral assemblage and interpretation of the results. Further, the small number of viral reference genomes available, coupled with short sequence read lengths might cause errors in virus identification. Despite these limitations and potential biases, the data show that viral communities associated with corals are diverse, with double- and single-stranded DNA and RNA viruses. The identified viruses are dominated by dsDNA-tailed bacteriophages, but there are also viruses that infect eukaryote hosts, likely the endosymbiotic dinoflagellates, Symbiodinium spp., host coral, and other eukaryotes in close association.
    Environmental Microbiology 03/2015; 17(10):3440-3449. DOI:10.1111/1462-2920.12803 · 6.20 Impact Factor
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