Immunological analysis of potato leaf roll luteovirus (PLRV) P1 expressionidentifies a 25 kDa RNA-binding protein derived via P1 processing

Mono- and polyclonal antibodies directed against different domains of the p otato leaf roil luteovirus (PLRV) P1 (ORF1) protein were applied to the ana lysis of P1 expression during PLRV replication in planta, Western analyses detected P1 and a protein of similar to 25 kDa (P1-C25) that accumulated to readily detectable amounts in PLRV-infected plants, but was not detected b y in vitro cell-free translation of P1, P1-C25 represents the C-terminus of P1 and is a proteolytic cleavage product produced during P1 processing, On the basis of its molecular weight, the N-terminus of P1-C25 is either iden tical to or located adjacent to the previously identified PLRV genome-linke d protein, VPg, P1-C25 is not associated with virus particles, and subcellu lar localization experiments detected P1-C25, but not P1, in the membrane a nd cytoplasmic fractions of PLRV-infected cells. In addition, P1-C25 exhibi ts nucleic acid-binding properties. On the basis of its biosynthesis, local ization and biochemical properties, P1-C25 may facilitate the formation of P1/PLRV RNA complexes in which the spatial proximity allows for covalent bo nd formation between PLRV RNA and VPg.