Cortical microtubule-associated ER sites: organization centers of cell polarity and communication

Anisotropic cell growth and the ability of plant cells to communicate within and across the borders of cellular and supracellular domains depends on the ability of the cells to dynamically establish polarized networks able to deliver structural and informational macromolecules to distinct cellular sites. Studies of organelle movements and transport of endogenous and viral proteins suggest that organelle and macromolecular trafficking pathways involve transient or stable interactions with cortical microtubule-associated endoplasmic reticulum sites (C-MERs). The observations suggest that C-MERs may function as cortical hubs that organize cargo exchange between organelles and allow the recruitment, assembly, and subsequently site-specific delivery of macromolecular complexes. We propose that viruses interact with such hubs for replication and intercellular spread.