Plants may not have a complex circulatory immune system like that of animals,but they do have a fairly sophisticated transport system that enables cell-to-cell communication as well as transport of water and solutes.This type of communication is key to the plants ability to regulate the spread of pathogenic microbes,mount responses to stress at distant sites,and regulate systemic signaling events.One cell-to-cell transport route is the symplastic route,which requires the plasmodesmata (PD),channels that traverse through cell walls and establish symplastic connections between adjacent cells.PD are formed during cytokinesis and can be simple or branched,and are delineated by a membrane that is continuous with the plasma membranes (PMs) of adjacent cells.PD contains a cylindrical inner component in the center of the pore,which is derived from the endoplasmic reticulum and is called the desmotubule.The space between the desmotubule and the PM acts as a cytoplasmic conduit that channels molecules across cells.