RNA silencingin plants and insects provides an antiviral defense and as a countermeasure most viruses
encode RNA silencing suppressors (RSS).For the family Rhabdoviridae, no detailed functional RSS studies
have been reported in plant hosts and insect vectors.In agroinfiltrated Nicotiana benthamiana leaves we
show for the first time for a cytorhabdovirus,lettuce necrotic yellows virus(LNYV),that one of the nucleocapsid core proteins,phosphoprotein(P)has relatively weak local RSS activity and delays systemic
silencing of a GFP reporter.Analysis of GFP small RNAs
indicated that the Pprotein did not prevent siRNA
accumulation. To explore RSS activity in insects,we used a Flock House virus replicon system in
Drosophila S2 cells.In contrast to the plant host,LNYV P protein did not exhibit RSS activity in the insect cells. Taken together our results suggest that P protein may target plant-specific components of RNA silencing post siRNA biogenesis.