ASGSB 1999 Annual Meeting Abstracts

MECHANOTRANSDUCTION AND THE PLANT CYTOSKELETON. R. Cyr and D. Fisher. Dept. Biology, Penn State, PA.

Plants cells have a functionally unique cortical microtubule array. This cortical array does not play a structural role in the cell, rather it provides spatial information to the cellulose synthase complexes residing within the membrane. In elongating plant cells, the cortical array is highly organized in a transverse orientation to the axis of elongation. These transversely oriented microtubules serve as templates to similarly orient the deposition of newly synthesized cellulose; transversely oriented cellulose then acts like hoops around a barrel to laterally constrain turgor forces so that cells expand in one axis. While it is clear that cortical microtubules affect the deposition of the plant’s extracellular matrix, it is not clear how they, themselves, obtain spatial information. We have been testing the hypothesis that cortical microtubules can use growth forces (mechanical strain) to affect their orientation. This has been tested using centrifuged protoplasts in which the centrifugal vector has been shown to affect the future axis of elongation; microtubules are required to cue to this force. We have extended these studies using agarose embedded protoplasts. By plating the agarose culture onto flexible sheets of Silastic we are able to apply strain and analyze how this force application affects the axis of elongation. We find that a relatively brief application of anisotropic strain is sufficient to cue the elongative axis in these cells. Moreover, we find that microtubules in these cells acquire order immediately after force application. These results will be discussed in terms of a model for plant morphogenesis whereby developmentally evoked mechanical strain feeds back to the cell to affect cellular morphogenesis. Thus, the data is consistent with a self-rectifying morphogenic system in which the cytoskeleton plays a key role in transducing the resultant forces of growth to maintain continued elongation in growing organs. (Supported by NASA NAG5-4840).

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