Abstract
Oriented cell divisions are significant in plant morphogenesis because plant cells are embedded in cell walls and cannot relocate. Cell divisions followvarious regular orientations, but the underlying mechanisms have not been clarified. We proposethat cell-shape-dependent self-organization of cortical microtubule arrays is able to provide a mechanism for determining planes of early tissue-generating divisions and may form the basis for robust control of cell division orientation in the embryo. To show this, we simulate microtubules on actual cell surface shapes, from which we derive a minimal set of three rules for proper array orientation. The first rule captures the effects of cell shape alone on microtubule organization, the second rule describes the regulation of microtubule stability at cell edges, and the third rule includes the differential effect ofauxin on local microtubule stability. These rules generate early embryonic division plane orientations and potentially offer a framework for understanding patterned cell divisions in plant morphogenesis.
Highlights
Plant cell division patterns show striking regularities
The orientation of the prophase band (PPB) and, by extension, that of the cortical microtubule array (CMA) is an indicator of cell division orientation [12, 13]
We focused on the impact of shape in a geometrical sense, including the described edge effects, on the collective dynamics of MTs that lead a global orientation of the CMA
Summary
Plant cell division patterns show striking regularities. A prime example is the early-stage embryo in Arabidopsis [1,2,3], which starting from the single-cell stage undergoes a few rounds of remarkably robust and geometrically precise internal divisions, setting the stage for further development through differentiation and growth. For already more than a century, these regularities have spurred the formulation of heuristic geometric rules for oriented cell divisions. These rules relate the selection of division planes, e.g., to the principal direction of growth, geometric relations to existing cell walls and the nucleus, or minimum cell surface energy [4,5,6,7,8,9]. With the advent of modern cell biology, division plane orientation in plants has been connected with the orientation of the ordered ensemble of microtubules (MTs) associated with the plasma membrane, the cortical microtubule array (CMA) [10, 11]. The question of how the CMA is organized is of prime importance to understanding division plane orientation
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