Microtubular and Cytoskeletal Mutants

Abstract

Microtubules are biochemically one of the simplest, yet functionally most important, cellular organelles in the plant and animal kingdoms. They are integral components of a dynamic, three-dimensional framework referred to as the cytoskeleton. In addition to a fundamental role in intracellular movement, the microtubule, microfilament and intermediate filament arrays of the cytoskeleton are networks upon which asymmetric distribution of subcellular constituents is established and from which these polarized regulatory molecules mediate morphogenesis. The functions of microtubules reflect this common theme of distribution and movement. In plants, four principal microtubular functions are recognized: determination of the division plane; translocation of chromosomes; cell plate/phragmoplast formation; and control of cell morphology. Obviously, from a biotechnological point of view, the ability to control and regulate these processes via modifications of the component parts will have a profound effect on plant growth and development. Microtubules are composed primarily of a single, repeating macromolecular unit — tubulin. Tubulin itself is a heterodimeric protein, composed of two similar subunits: alpha-(α) and beta-(β)tubulin. The α- and β-tubulins are typically encoded by gene families, and these give rise to various tubulin isotypes that are differentially expressed and modified during growth and development. In addition, a ubiquitous and diverse class of proteins that bind to microtubules, known as microtubule associated proteins (MAPs), are believed to be important in nucleation, stabilization and bundling of microtubules.