The remaining fenestrae contain strands of endoplasmic reticulum passing through them, and are thought to be the precursors of plasmodesmata [ 8 ].
22.
Plant cells are surrounded by solid cell walls, therefore transport through plasmodesmata is the preferred path for virions to move between plant cells.
23.
Movement through the plasmodesmata occurs for cell-to-cell transfers but the phloem is utilized for long distance movement within the plant.
24.
Plants with a polymer-trapping mechanism may have an abundance of plasmodesmata, but this trait alone does not indicate this loading strategy.
25.
Although cell walls are permeable to small soluble proteins and other solutes, plasmodesmata enable direct, regulated, symplastic transport of substances between cells.
26.
Plasmodesmata are also used by cells in phloem, and symplastic transport is used to regulate the sieve-tube cells by the companion cells.
27.
Consequently the virus must modify the plasmodesmata as they, themselves, are too large to fit through the small and tightly regulated plant structure.
28.
Most plant viruses move between plant cells via plasmodesmata, pores between plant cell walls that allow the plant cells to communicate with each other.
29.
The movement proteins of many plant viruses form a transport tubule within the pore of the plasmodesmata that allows the transport of mature virus particles.
30.
While the presence of abundant plasmodesmata does allow for passive, symplastic transport, it does not exclude the possibility of active, apoplastic transport.
