Abstract
RNA silencing describes a pan-eukaryotic pathway of gene regulation where doubled stranded RNA are processed by the RNAse III enzyme Dicer or homologs. In particular, plants use it as a way to defend themselves against pathogen invasions. In turn, to evade the plant immune response, viruses have developed anti-RNA silencing mechanisms. They may indeed code for proteins called "viral suppressor of RNA silencing" which block the degrading of viral genomic or messenger RNA by the plant. The Rice Mottle Virus is an African virus of the sobemovirus family, which attacks the most productive rice varieties cultivated on this continent. It encodes P1, a cysteine-rich protein described as a potential RNA silencing suppressor. P1 is a 157 amino-acid long protein, characterized by a high propensity to aggregate concomitant with a limited stability with time in the conditions used in structural studies. To overcome this problem, shorter fragments were also studied. This strategy enabled the assignment of more than 90% backbone resonances of P1. This assignment should set the base of future NMR investigation of the protein structure and of its interactions with rice cellular partners.