Tobacco Necrosis Virus-A Single Coat Protein Amino Acid Substitutions Determine Host-Specific Systemic Infections of and Soybean.

Plant viruses often infect several distinct host species. Sometimes, viruses can systemically infect a specific host whereas, in other cases, only local infections occur in other species. How viral and host factors interact to determine systemic infections among different hosts is largely unknown, particularly for icosahedral positive-stranded RNA viruses. The Chinese isolate belongs to the genus in the family . In this study, we investigated variations in systemic infections of tobacco necrosis virus-A (TNV-A) in and (soybean) by alanine-scanning mutagenesis of the viral coat protein (CP), which is essential for systemic movement of TNV-A. We found that three amino acids, R, K, and Q, are key residues that mediate varying degrees of systemic infections of and soybean. Further analysis revealed that variations in systemic trafficking of TNV-A CP mutants in and soybean are associated with virion assembly and stability. The CP amino acids K and Q are highly conserved among all TNV-A isolates and are replaced by Q and K in the TNV-D isolates. We demonstrated that systemic infectivity of either TNV-A K177A and Q233A or K177Q and Q233K mutants are correlated with the binding affinity of the mutated CPs to the host-specific Hsc70-2 protein. These results expand our understanding of host-dependent long-distance movement of icosahedral viruses in plants.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.