Common and strain-specific post-translational modifications of the potyvirus Plum pox virus coat protein in different hosts

Phosphorylation and O-GlcNAcylation are widespread post-translational modifications (PTMs) often sharing protein targets. Numerous studies have reported phosphorylation of plant virus proteins. In plants, research on O-GlcNAcylation lags behind regarding other eukaryotes and information about O-GlcNAcylated plant viral proteins is extremely scarce. The potyvirus Plum pox virus (PPV) causes sharka disease in Prunus trees, and also infects a wide range of experimental hosts. Capsid protein (CP) from virions of the PPV-R isolate purified from herbaceous plants can be extensively modified by O-GlcNAcylation and phosphorylation. In this study, a combination of proteomics and biochemical approaches has been employed to broaden knowledge of PPV CP PTMs. CP proved to be modified regardless it is assembled or not in mature particles. PTMs of CP occur in the natural host Prunus persica, similar to what happens in herbaceous plants. Additionally, we observe O-GlcNAcylation and phosphorylation are general features of different PPV strains, suggesting that roles of these modifications are part of overall strategies deployed during plant-virus interactions. Interestingly, phosphorylation at a casein kinase II motif conserved among potyviral CPs exhibits strain specificity in PPV; however, it does not display the critical role attributed to same modification in the CP of another potyvirus, Potato virus A.