Virulence domain of the RYMV genome-linked viral protein VPg towards rice rymv1–2-mediated resistance

Virulent variants of Rice yellow mottle virus (genus Sobemovirus) can emerge on the highly resistant rice cultivars Gigante and Bekarosaka. Non-synonymous mutations responsible for the breakdown of the recessive resistance gene rymv1-2 were located in the VPg after determination of its termini in the polyprotein P2a. The secondary structure of this protein was predicted to include a central alpha-helix. The two major amino acids related to virulence are located on the same side of this helix. The 3D topology and the biochemical properties of virulence mutations both suggested a direct site-to-site interaction between RYMV VPg and rice eIF(iso)4G encoded by rymv1.