Negative-strand tospoviruses and tenuiviruses carry a gene for a suppressor of gene silencing at analogous genomic positions.

Abstract

Posttranscriptional silencing of a green fluorescent protein (GFP) transgene in Nicotiana benthamiana plants was suppressed when these plants were infected with Tomato spotted wilt virus (TSWV), a plant-infecting member of the BUNYAVIRIDAE: Infection with TSWV resulted in complete reactivation of GFP expression, similar to the case for Potato virus Y, but distinct from that for Cucumber mosaic virus, two viruses known to carry genes encoding silencing suppressor proteins. Agrobacterium-based leaf injections with individual TSWV genes identified the NS(S) gene to be responsible for the RNA silencing-suppressing activity displayed by this virus. The absence of short interfering RNAs in NS(S)-expressing leaf sectors suggests that the tospoviral NS(S) protein interferes with the intrinsic RNA silencing present in plants. Suppression of RNA silencing was also observed when the NS3 protein of the Rice hoja blanca tenuivirus, a nonenveloped negative-strand virus, was expressed. These results indicate that plant-infecting negative-strand RNA viruses carry a gene for a suppressor of RNA silencing.