Building a functional endoplasmic reticulum for proper cell growth and stress responses: a plant perspective

The endoplasmic reticulum (ER) is an interconnected network of membrane-bound tubules and sheets stretching throughout the cytoplasm of all eukaryotic cells including plant cells. The ER is highly dynamic and undergoes constant remodelling. A properly formed ER is essential for cell growth, development and cellular responses to stresses. It is known that the dynamics of the cytoskeleton is linked to the formation and/or remodelling of a functional ER. Over the past 20 years, research has revealed that a set of ER localized ER-shaping proteins play crucial roles in building a functional ER. Recent research also indicates that maintaining a functional ER, in particular under stressful conditions, requires a proper turnover of the ER mediated by selective autophagy of the ER. In this review, we discuss the current understanding of functions of reticulons and atlastins, two classes of ER-shaping proteins in the formation of the ER in both animal and plant cells, with an emphasis on the plant system. We also discuss how the two classes of proteins may interplay to maintain a proper ER and how their actions may be regulated. Finally, we briefly mention how autophagy of the ER may be regulated during cell development and stress responses.