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The cells of plants, bacteria and fungi all share the common feature of being surrounded by a rigid cell wall.  In order for these cells to grow and to achieve functional shape, the synthesis and expansion of these constraining walls must be carefully regulated in space and time.
Across this diverse range of phylogenetic distance and cell size, the cytoskeleton is emerging as a key engine for regulating processes at the cell membrane that underlie wall synthesis and expansion.  In recent years we have shown that the cortical microtubule cytoskeleton acts to position the secretion of cellulose synthase complexes and to guide their trajectories as cellulose is extruded into the cell wall.
Outstanding questions include what other roles the microtubule cytoskeleton may play in organizing the membrane and cell periphery, and if the wall or its synthesis may also act as an organizer.  Here, we develop an assay for visualizing discreet secretory events in Arabidopsis, and find that microtubules serve to position secretion generally, as does cellulose synthesis itself, defining linear and dynamic secretory microdomains at the plasma membrane of expanding cells.  We also ask if cortical microtubules serve to constrain the motions of other membrane proteins, and find evidence that cortical microtubules can act as diffusional barriers, acting together with the cell wall to constrain membrane protein mobility.