Uncovering new abilities of RNA silencing suppressors from viruses of the Potyviridae family

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• Adrian Valli, Gene Silencing Group
• Friday 28 October 2011, 13:00-13:30
• Department of Plant Sciences, Large Lecture Theatre.

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RNA silencing mediated by siRNAs plays an important role as an antiviral mechanism in plants and other eukaryotic organisms. Among the strategies that viruses have developed to counteract this defensive barrier, the acquisition of RNA silencing suppression activity by one or several viral products appears to be most largely spread. Along the consecution of my PhD at the National Centre of Biotechnology (Madrid, Spain), we found that the ipomovirus Cucumber vein yellowing virus (CVYV) differs from most members of the family Potyviridae in lacking the typical silencing suppressor HCPro, which is replaced by an unrelated protein, P1b. we have reported that P1b, similarly to potyviral HCPro, shows anti-silencing activity by forming complexes with 21-nt long siRNAs. In the talk I am going to show those results obtained along the last stage of my stay in Madrid:

- Making use of a chimerical Plum pox virus (PPV) we demonstrated that P1b can functionally replace HCPro to properly infect model plants (e.g. Nicotiana benthamiana), being essential its silencing suppression activity to start the infectious process. More importantly, since P1b-carrying PPV was able to infect cucumber, which is the natural host of CVYV and a non-host of wild type PPV , a key role in host range definition is proposed for potyviral RNA silencing suppressors.

- Studies of viral infectivity showed that extracts of N. benthamiana infected with the chimerical P1b-carrying PPV had a strong defect to initiate an infection de novo. Given that this ability could be restored by the expression of PPV HC Pro in trans, but not by the action of either HCPro from Tobacco each virus or the strong suppressor P19 from Tobacco bushy stunt virus, it suggests we have discovered a new putative (silencing-unrelated) function for HCPro.

This talk is part of the Plant Sciences Research Seminars series.

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