Microtubules, cell wall deposition and the determination of plant cell shape

Abstract

THE shape of Plant cells depends largely on the orientation of cellulose microfibrils in their cell walls1. In almost all cells where the microfibrils are regularly arranged, cortical microtubules lie parallel to the wall microfibrils. Experimental evidence indicates that these microtubules influence the arrangement of the deposition of wall microfibrils2. How microtubules determine the orientation of microfibrillar deposition is not yet known3,4, but it has been speculated that they may influence the alignment of cellulose synthetase enzymes on the Plasma membrane5. Microtubules act as a cytoskeleton in the formation and maintenance of cell shape in many types of cells6 including Plant cells which lack a cell wall7, or before a wall is deposited8, and it may be that microtubules, in those Plant cells where they are arranged congruently with recently deposited wall microfibrils, directly determine cell shape. However, using coumarin to inhibit cell wall regeneration by protoplasts of Mougeotia I demonstrate here the inability of microtubules to directly determine cell shape.