Abstract:
Intercellular transport of viruses through cytoplasmic connections, termed plasmodesmata (PD), is essential for systemic
infection in plants by viruses. Previous genetic and ultrastructural data revealed that the potyvirus cyclindrical inclusion (CI)
protein is directly involved in cell-to-cell movement, likely through the formation of conical structures anchored to and
extended through PD. In this study, we demonstrate that plasmodesmatal localization of CI in N. benthamiana leaf cells is
modulated by the recently discovered potyviral protein, P3N-PIPO, in a CI:P3N-PIPO ratio-dependent manner. We show that
P3N-PIPO is a PD-located protein that physically interacts with CI in planta. The early secretory pathway, rather than the
actomyosin motility system, is required for the delivery of P3N-PIPO and CI to PD. Moreover, CI mutations that disrupt virus
cell-to-cell movement compromise PD-localization capacity. These data suggest that the CI and P3N-PIPO complex
coordinates the formation of PD-associated structures that facilitate the intercellular movement of potyviruses in infected
plants.
