From Hypo- to Hypersuppression: Effect of Amino Acid Substitutions on the RNA-Silencing Suppressor Activity of the Tobacco etch potyvirus HC-Pro by ProQuest

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RNA silencing participates in several important functions: from the regulation of cell metabolism and organism development to sequence-specific antiviral defense. Most plant viruses have evolved proteins that suppress RNA silencing and that in many cases are multifunctional. Tobacco etch potyvirus (TEV) HC-Pro protein suppresses RNA silencing and participates in aphid-mediated transmission, polyprotein processing, and genome amplification. In this study, we have generated 28 HC-Pro amino acid substitution mutants and quantified their capacity as suppressors of RNA silencing in a transient expression assay. Most mutations either had no quantitative effect or completely abolished silencing suppression (10 in each class), 3 caused a significant decrease in the activity, and 5 significantly increased it, revealing an unexpected high frequency of mutations conferring hypersuppressor activity. A representative set of the mutant alleles, containing both hypo- and hypersuppressors, was further analyzed for their effect on TEV accumulation and the strength of induced symptoms. Whereas TEV variants with hyposuppressor mutants were far less virulent than wild-type TEV, those with hypersuppressor alleles induced symptoms that were not more severe than those characteristic of the wild-type virus, suggesting that there is not a perfect match between suppression and virulence. [PUBLICATION ABSTRACT]

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									Copyright Ó 2008 by the Genetics Society of America
DOI: 10.1534/genetics.108.091363



From Hypo- to Hypersuppression: Effect of Amino Acid Substitutions on the
  RNA-Silencing Suppressor Activity of the Tobacco etch potyvirus HC-Pro

            Clara Torres-Barcelo, Susana Martın, Jose-Antonio Daros and Santiago F. Elena1
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      Instituto de Biologıa Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientıficas-UPV, 46022 Valencia, Spain
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                                                         Manuscript received May 13, 2008
                      
								
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