Cytoskeleton and Cell Morphogenesis

A complex network of filamentous proteins "the cytoskeleton" is intimately involved in cell division, cell growth and differentiation and sub-cellular, organelle motility. In plants two major cytoskeletal elements are recognized; actin microfilaments and microtubules. The fusion of nucleotide sequences encoding actin-binding or microtubule binding proteins to fluorescent proteins like the Green Fluorescent Protein (GFP) has made it possible to visualize the cytoskeleton, its functioning and regulation in live plant cells.

	Changes in cell shape in response to cytoskeleton perturbation; green-normal, orange-microtubule defective, white-actin defective.

This section provides a brief glimpse into the pivotal role played by the cytoskeleton in cell shape development in higher plants.

A massive body of literature has accumulated on cytoskeletal involvement in plant cell morphogenses and has been reviewed recently.

General observations from a variety of cytoskeletal-drug treatments and mutant cell studies in different model cell types such as trichomes, root-hairs, hypocotyl-cells are summarized in the interactive figure and suggest the following:

Aberrant microtubule cytoskeleton activity results in a loss of growth directionality. Affected cells tend to grow isotropically and present a generally rounded and swollen appearance.

Aberrant actin cytoskeleton activity results in less cellular expansion producing short cells. Alternatively, cells may have abnormal regional expansion defects leading to odd shapes.

Recent publications have identified some of the regulatory molecules that affect the actin and microtubule cytoskeleton. A general model has been proposed. Some interesting parallels suggesting high functional similarity between animal cell forward movement and plant cell extention growth have emerged from our cytoskeletal work. Amongst the different actin cytoskeleton regulators that our lab is currently investigating is the putative ARP2/3 complex and its upstream regulators, as well as the actin bundling protein fimbrin.

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References
Mathur. Cell shape development in plants. TRENDS IN PLANT SCIENCE. 9 (12): 583-590. December, 2004.
Mathur. The ARP2/3 complex: giving plant cells a leading edge. BIOESSAYS. 27(4). 377-387. April 2005.