Together with movement protein P3a, facilitates long-distance movement of virions in host (By similarity). Transports viral genome to neighboring plant cells directly through plasmosdesmata, without any budding (Probable). The movement protein allows efficient cell to cell propagation, by bypassing the host cell wall barrier (Probable). Binds ssRNA (By similarity). Homodimer. The N-terminus is involved in homodimerization (By similarity). The C-terminus binds ssRNA (By similarity). The C-terminus is phosphorylated (By similarity). Phosphorylated. Poleroviruses are transmitted by aphids directly into phloem tissue. The virus replicates most efficiently in phloem companion cells and then moves through plasmodesmata between companion cells or into sieve elements for long distance transport. Belongs to the polerovirus movement protein family.