Abstract
Phosphorylation and O-GlcNAcylation are widespread post-translational modifications (PTMs), often sharing protein targets. Numerous studies have reported the phosphorylation of plant viral proteins. In plants, research on O-GlcNAcylation lags behind that of 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 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 was employed to broaden knowledge of PPV CP PTMs. CP proved to be modified regardless of whether or not it was assembled into mature particles. PTMs of CP occurred in the natural host Prunus persica, similarly to what happens in herbaceous plants. Additionally, we observed that O-GlcNAcylation and phosphorylation were general features of different PPV strains, suggesting that these modifications contribute to general strategies deployed during plant-virus interactions. Interestingly, phosphorylation at a casein kinase II motif conserved among potyviral CPs exhibited strain specificity in PPV; however, it did not display the critical role attributed to the same modification in the CP of another potyvirus, Potato virus A.
Highlights
Numerous viral proteins can be post-translationally modified at different stages of infection, probably a result of co-evolutionary strategies, whereby viruses acquire the ability to hijack host enzymes [1]
O-GlcNAcylation and Phosphorylation of Plum pox virus (PPV) capsid protein (CP) Affect Protein not Assembled in Mature
N. benthamiana plants were inoculated with a PPV-R cDNA clone, pSN-PPV, and systemically infected leaves were homogenized in a phosphate buffer
Summary
Numerous viral proteins can be post-translationally modified at different stages of infection, probably a result of co-evolutionary strategies, whereby viruses acquire the ability to hijack host enzymes [1]. There are abundant examples of proteins of animal viruses that are targeted by phosphorylation [2,3,4,5], one the most widespread post-translational modifications (PTMs), which dynamically regulate functions of a large number of cellular proteins. Many viral products of viruses infecting plants, both non-structural [6,7,8,9,10,11,12] and structural [13,14,15,16,17] proteins, have been found to be modified by phosphorylation. The main open reading frame (ORF) of potyviral genomic RNA is translated into a large polyprotein, which includes the CP at its C-end, and it is proteolytically processed by three
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