THE PLANT GOLGI-APPARATUS

The plant Golgi apparatus has an important role in protein glycosylati on and sorting, but is also a major biosynthetic organelle that synthe sises large quantities of cell wall polysaccharides. This is reflected in the organisation of the Golgi apparatus as numerous individual sta cks of cisternae that are dispersed through the cell. Each stack is po larised: the shape of the cisternae and the staining of the membranes change in a cis to trans direction, and the cisternae on the trans sid e contain more polysaccharides. Numerous glycosyltransferases are requ ired for the synthesis of the complex cell wall polysaccharides. Micro scopy and biochemical fractionation studies suggest that these enzymes are compartmentalised within the stack. Although there is no obvious cir Golgi network, the trans-most cisterna or trans Golgi network ofte n buds clathrin-coated and sometimes smooth dense vesicles as well. He re, vacuolar proteins are sorted from the secreted proteins and polysa ccharides. This review highlights unique aspects of the organisation a nd function of the plant Golgi apparatus. Fundamentally similar proces ses probably underlie Golgi organisation in all organisms, and conside ration of the plant Golgi specialisations can therefore be generally i nformative, as well as being of central importance to plant cell biolo gy. (C) 1998 Elsevier Science B.V. All rights reserved.