The Morphology and Dynamics of the ER

Abstract

The endoplasmic reticulum (ER) is a non-uniform compartment in plants as re- gards its morphology and function. It extends as a highly anastomosing membranous network throughout the cytoplasm, is the major compartment of membrane biogenesis, and has been verified to function as the starting site for the secretory pathway. Early elec- tron microscopy studies revealed three morphological ER sub-domains: the smooth ER, the rough ER, and the nuclear envelope. In the last two decades vital staining proced- ures, immunological methods, and green fluorescent protein technology in connection with confocal laser scanning microscopy have extended and augmented our knowledge regarding the morphology of the different ER domains, especially the three-dimensional transition between the cortical tubular network, long tubular strands, and lamellar sheets during interphase and mitosis. The cytoskeleton in connection with the respective motor proteins and cations like Ca2+ and H+ play a critical role in the regulation of ER organi- zation in dividing, differentiating, and stressed cells. Although our understanding of ER morphology in plants has improved notably, our view still remains founded on a rather limited number of model cells.