Abstract: The plant xylem is one of the most important evolutionary innovations for terrestrial life, as it allowed plants to adapt and growth to significant stature. The xylem cells are encased by thickened cell walls that reinforce them and that are typically organized in spiraling or reticulate patterns. These wall types are largely assembled from the polysaccharide cellulose, which is synthesized at the plasma membrane by large cellulose synthase (CesA) complexes. The CesAs move along linear tracks at the plasma membrane, which is likely due to the catalytic activity of the proteins. The direction of the CesA movement is thought to be steered by cortical microtubules via the protein Cellulose Synthase Interacting (CSI)1; however, this is not clarified for secondary wall synthesis. In addition, it is unclear how the microtubules are re-arranged to support patterns of the cell walls and how this transition affect cellulose synthesis. In this talk I will outline how microtubules re-arrange themselves to support the transition between primary and secondary wall cellulose synthesis. These results will provide a framework to understand how patterned secondary walls emerge.
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