Abstract
The endoplasmic reticulum (ER) is a membrane-bounded organelle whose membrane comprises a network of tubules and sheets. The formation of these characteristic shapes and maintenance of their continuity through homotypic membrane fusion appears to be critical for the proper functioning of the ER. The atlastins (ATLs), a family of ER-localized dynamin-like GTPases, have been identified as fusogens of the ER membranes in metazoans. Mutations of the ATL proteins in mammalian cells cause morphological defects in the ER, and purified Drosophila ATL mediates membrane fusion in vitro. Plant cells do not possess ATL, but a family of similar GTPases, named root hair defective 3 (RHD3), are likely the functional orthologs of ATLs. In this review, we summarize recent advances in our understanding of how RHD3 proteins play a role in homotypic ER fusion. We also discuss the possible physiological significance of forming a tubular ER network in plant cells.
Highlights
Homotypic fusion of endoplasmic reticulum membranes in plant cellsReviewed by: Lorenzo Frigerio, University of Warwick, UK Etsuo Yokota, University of Hyogo, Japan
The endoplasmic reticulum (ER) is the origin of the endomembrane system in eukaryotic cells
Though the sheets may be stacked by helicoidal membrane motifs (Terasaki et al, 2013), tubules often extend from sheets and are connected via three-way junctions into a reticular network (Lee and Chen, 1988; Hu et al, 2008)
Summary
Reviewed by: Lorenzo Frigerio, University of Warwick, UK Etsuo Yokota, University of Hyogo, Japan. The endoplasmic reticulum (ER) is a membrane-bounded organelle whose membrane comprises a network of tubules and sheets. The formation of these characteristic shapes and maintenance of their continuity through homotypic membrane fusion appears to be critical for the proper functioning of the ER. Mutations of the ATL proteins in mammalian cells cause morphological defects in the ER, and purified Drosophila ATL mediates membrane fusion in vitro. Plant cells do not possess ATL, but a family of similar GTPases, named root hair defective 3 (RHD3), are likely the functional orthologs of ATLs. In this review, we summarize recent advances in our understanding of how RHD3 proteins play a role in homotypic ER fusion.
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