Viral Movement Proteins and Plasmodesmata: turning gatekeepers into gateways

Plant viruses have evolved diverse strategies for cell-to-cell and systemic movement, utilizing various viral proteins and cellular components and pathways. They typically encode one or a small group of proteins called movement proteins that mediate their local cell-to-cell movement via plasmodesmata (PD). Other virus-encoded proteins also make important contributions to viral transit through PD. Movement and other viral proteins use various cellular pathways to mediate their localization to and transit through PD. This review summarizes current understanding of these pathways and mechanisms with a focus on movement proteins and their interactions with host factors.