An evolutionary perspective on the nucleocytoplasmic shuttling mechanism of duck plague virus UL54 protein.

Duck plague virus (DPV), a member of the alpha-herpesvirus, causes duck plague (DP), thereby posing a serious threat to the waterfowl industry. The DPV UL54-encoded protein shuttles between the nucleus and cytoplasm to modulate viral replication. However, the role of the UL54 protein in the evolutionary process remains unknown. This study is conducted from an evolutionary perspective to explore the nuclear-cytoplasmic shuttling characteristic of UL54 protein. First, we analyzed the co-evolution on DPV whole genome and its UL54 gene using molecular evolutionary methods. Next, we constructed phylogenetic trees based on UL54 nucleotide sequences and the corresponding amino-acid sequences from different alpha-herpesvirus stains. Based on these phylogenetic trees, we selected strains that are genetically close to DPV, and performed UL54 gene sequence alignment between DPV and those phylogenetically related strains. Then, we discovered there were specific mutation sites in UL54 gene of DPV. Finally, we constructed recombinant plasmids with genetic mutations to detect the influence of mutation sites on the nuclear-cytoplasmic shuttling property of the UL54-encoded proteins. The results showed that DPV exhibited dual modes comprising co-evolution with its natural hosts and cross-species transmission, meanwhile UL54 genes from different viral strains exhibited marked evolutionary divergence. Further investigation revealed there were three specific mutation sites (Lys269, Leu348 and Leu377) in UL54 amino acid sites, which were correlated with evolution of DPV. Mutation at these sites significantly impacted the nuclear-cytoplasmic shuttling property of the UL54-encoded protein. Our study provides a rationale for understanding the evolutionary mechanism of DPV and exploring new therapeutic strategy.