Determination of Protein Interactions among Replication Components of Apple Necrotic Mosaic Virus

Apple mosaic disease is one of the most widely distributed and destructive diseases in apple cultivation worldwide, especially in China, whose apple yields account for more than 50% of the global total. Apple necrotic mosaic virus (ApNMV) is a newly identified ilarvirus that is closely associated with apple mosaic disease in China; however, basic viral protein interactions that play key roles in virus replication and the viral life cycle have not been determined in ApNMV. Here, we first identify an ApNMV-Lw isolate that belongs to subgroup 3 in the genus Ilarvirus. ApNMV-Lw was used to investigate interactions among viral components. ApNMV 1a and 2a^pol, encoded by RNA1 and RNA2, respectively, were co-localized in plant cell cytoplasm. ApNMV 1a interacted with itself at both the inter- and intramolecular levels, and its N-terminal portion played a key role in these interactions. 1a also interacted with 2a^pol, and 1a's C-terminal, together with 2a^pol's N-terminal, was required for this interaction. Moreover, the first 115 amino acids of 2a^pol were sufficient for permitting the 1a-2a^pol interaction. This study provides insight into the protein interactions among viral replication components of ApNMV, facilitating future investigations on its pathogenicity, as well as the development of strategies to control the virus and disease.