The measurement of exocytosis in plant cells

Abstract

Exocytosis is of vital importance to the growth and development of plant cells. It is a dynamic process in which vesicles bearing polysaccharide precursors and proteins fuse with the plasma membrane and release their contents. Equally important, new plasma membrane is delivered by exocytosis as secretory vesicle membrane becomes incorporated. The requirements for polysaccharides, proteins and plasma membrane are very different in different cell types, so there must be sophisticated mechanisms for ensuring delivery of these materials to the correct cellular locations at the appropriate time and, particularly in the case of membrane, their recovery and recycling. Currently, little is known of these mechanisms in plants, but new methods for measuring exocytosis are under development, and existing techniques have already contributed data of considerable relevance. Here the methods for measuring exocytosis are described and evaluated, with emphasis on the electrophysiological measurement of capacitance as a relatively non-invasive method, and on cell-free assays because of their potential importance in the identification of proteins and other factors that control exocytosis in plant cells.