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SUMMARY:Uncovering new abilities of RNA silencing suppressors from viruses
  of the Potyviridae family - Adrian Valli\, Gene Silencing Group
DTSTART:20111028T120000Z
DTEND:20111028T123000Z
UID:TALK33414@talks.cam.ac.uk
CONTACT:24938
DESCRIPTION:RNA silencing mediated by siRNAs plays an important role as an
  antiviral mechanism in plants and other eukaryotic organisms. Among the s
 trategies 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 o
 f my PhD at the National Centre of Biotechnology (Madrid\, Spain)\, we fou
 nd that the ipomovirus Cucumber vein yellowing virus (CVYV) differs from m
 ost members of the family Potyviridae in lacking the typical silencing sup
 pressor HCPro\, which is replaced by an unrelated protein\, P1b. we have r
 eported that P1b\, similarly to potyviral HCPro\, shows anti-silencing act
 ivity by forming complexes with 21-nt long siRNAs.\nIn the talk I am going
  to show those results obtained along the last stage of my stay in Madrid:
 \n\n- 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 activit
 y to start the infectious process. More importantly\, since P1b-carrying P
 PV was able to infect cucumber\, which is the natural host of CVYV and a n
 on-host of wild type PPV\, a key role in host range definition is proposed
  for potyviral RNA silencing suppressors.\n\n- Studies of viral infectivit
 y showed that extracts of N. benthamiana infected with the chimerical P1b-
 carrying PPV had a strong defect to initiate an infection de novo. Given t
 hat this ability could be restored by the expression of PPV HCPro in trans
 \, but not by the action of either HCPro from Tobacco each virus or the st
 rong suppressor P19 from Tobacco bushy stunt virus\, it suggests we have d
 iscovered a new putative (silencing-unrelated) function for HCPro.\n
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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