Identification of the RNA silencing suppressor activity of Sugarcane streak mosaic virus P1 gene

Abstract

In the present study, P1 gene of Sugarcane streak mosaic virus (SCSMV) has been proved to govern the RNA silencing suppressor activity. Agrobacterium-mediated transient expression assay with Green Fluorescent Protein (GFP) has confirmed the RSS activity of P1 gene in the model plant Nicotiana tabaccum. The qRT-PCR analysis also confirmed the RSS activity of P1 gene of SCSMV infecting sugarcane. Further, the presence of conserved motif “WG” in the P1 protein across the 10 Indian isolates of SCSMV reiterates its role as RNA silencing suppressor of the Poacevirus. Although the Helper Component-Proteinase gene (HC-Pro) has been reported to govern the RSS activity in most of the viruses of the family Potyviridae, it does not show any such activity in the SCSCMV infecting sugarcane. The absence of “WG” motif across the 16 Indian isolates of SCSMV and low level of GFP expression in the Agrobacterium-mediated transient expression assay have clearly demonstrated lack of RSS activity in the HC-Pro gene of SCSMV. Thus, mosaic-resistant cultivars can be developed by targeting the P1 gene of SCSMV through RNAi approach.