Comparative Analysis of RNAi Suppression Activity of Proteins from Two Disparate Viruses

Abstract

RNAi is an efficient surveillance machinery that plays a robust defensive role in shielding plant and animal hosts against viral infections. In counter-defense viruses encode suppressor proteins that have the ability to restrict the RNAi machinery to ensure successful systemic invasion. The B2 protein of insect Flock House Virus (FHV-B2) and AC2 protein of Mungbean Yellow Mosaic India Virus (MYMIV-AC2) are two well-characterized suppressors of RNAi, capable of reversing reporter gene silencing. In this study, we compared the strength of the two suppressors by assaying for the degree of RNAi reversion and the duration of sustaining the reversal in planta. The suppression activity was observed by assaying for GFP fluorescence at 3 dpi, 7 dpi and 14 dpi. The phenotypic observations were corroborated with small RNA Northern Blotting and semi-quantitative RT-PCR. The results indicate that suppressor strength of FHVB2 is comparable to MYMIV-AC2, although they are encoded by virus infecting host from two different eukaryotic kingdoms. This study will provide new insights to dissect the conservation in the RNAi pathways during the host-virus interactions.