Spatial organization of xylem cell walls by ROP GTPases and microtubule-associated proteins.

Proper patterning of cellulosic cell walls is critical for cell shaping and differentiation of plant cells. Cortical microtubule arrays regulate the deposition patterns of cellulose microfibrils by controlling the targeting and trajectory of cellulose synthase complexes. Although some microtubule-associated proteins (MAPs) regulate the arrangement of cortical microtubules, knowledge about the overall mechanism governing the spacing of cortical microtubules is still limited. Recent studies reveal that ROP GTPases and MAPs spatially regulate the assembly and disassembly of cortical microtubules in developing xylem cells, in which localized secondary cell walls are deposited. Here, we review recent insights into the regulation of xylem cell wall patterning by cortical microtubules, ROP GTPases, and MAPs.