Functionality of potato virus Y coat protein in cell-to-cell movement dynamics is defined by its N-terminal region

Potato virus Y (PVY) is one of the top 10 economically most important plant viruses and responsible for major yield losses. We previously suggested the involvement of the N-terminal region of PVY coat protein (CP) in PVY spread. By constructing different N-terminal deletion mutants of the PVY N605 strain, we here show that deletions of 40 or more amino acid residues from the N-terminal region of the CP resulted in the PVY multiplication limited to primary infected cells in Nicotiana clevelandii plants. Deletion of 26 residues profoundly impaired PVY cell-to-cell movement and prevented systemic PVY spread, while deletions of 19-23 residues allowed delayed systemic PVY spread. Introduced point mutations in the identified region prevent (S21G) or delay (G20P) PVY movement. In summary, this work shows the significance of the CP N-terminus for movement of the PVY. IMPORTANCE Potato virus Y (PVY) is one of the most economically important plant viruses worldwide, since it causes major yield losses in Solanaceae, especially in potato, where it is the causal agent of potato tuber necrosis ringspot disease, negatively impacting tuber quality and significantly reducing potato yield. By constructing different PVY N-terminal deletion mutants, we identified the regions of the coat protein that are important for efficient PVY cell-to-cell movement. Understanding these regions, responsible for cell-to-cell as well as long-distance movement, is crucial for economically important plant viruses such as PVY, since dissolving such complex processes will enhance our understanding of the PVY infective cycle and contribute to the development of effective tackling strategies against PVY infections in potato and prevent yield losses.