Roles and regulation of plant cell walls surrounding plasmodesmata

• Callose and a distinct distribution of pectin characterize cell walls at PD sites.
• Cell wall remodelling enzymes target PD to regulate its form and function.
• Callose turnover is a dynamic process essential in the regulation of PD transport.
• Small signalling molecules trigger changes in cell walls to regulate PD aperture.

In plants, the intercellular transport of simple and complex molecules can occur symplastically through plasmodesmata. These are membranous channels embedded in cell walls that connect neighbouring cells. The properties of the cell walls surrounding plasmodesmata determine their transport capacity and permeability. These cell wall micro-domains are enriched in callose and have a characteristic pectin distribution. Cell wall modifications, leading to changes in plasmodesmata structure, have been reported to occur during development and in response to environmental signals. Cell wall remodelling enzymes target plasmodesmata to rapidly control intercellular communication in situ. Here we describe current knowledge on the composition of cell walls at plasmodesmata sites and on the proteins and signals that modify cell walls to regulate plasmodesmata aperture.