Search

Sar1 is a small GTPase of the ARF family. Upon exchange of GDP for GTP, Sar1 associates with the endoplasmic reticulum (ER) membrane and recruits COPII components, orchestrating cargo concentration and membrane deformation. Many aspects of the role of Sar1 and regulation of its GTP cycle remain unclear, especially as complexity increases in higher organisms that secrete a wider range of cargoes. This review focusses on the regulation of GTP hydrolysis and its role in coat assembly, as well as the mechanism of Sar1-induced membrane deformation and scission. Finally, we highlight the additional specialisation in higher eukaryotes and the outstanding questions on how Sar1 functions are orchestrated., (© 2023 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Cuticular waxes synthesised in the endoplasmic reticulum of epidermal cells must be exported to the outer surface of the epidermis to fulfil their barrier function. Beyond transmembrane trafficking mediated by ABC transporters, little is known about the movement of wax molecules. In this study, we characterise a mutant named sugar-associated vitrified 1 (sav1), which exhibits a vitrified phenotype and displays a reduced root length when cultivated on sugar-free medium. The mutation in SAV1, which encodes the protein Sec. 24C, leads to ultrastructural alterations in cuticle membranes, decreased deposition of epicuticular wax crystals, and modifications in the chemical composition of very-long-chain fatty acids in cuticular waxes. SAV1 is a membrane protein and expressed during the early stages of seedling development. The defective phenotype of sav1-1 in sugar-free medium resembles that of abcg5, which encodes an ATP-BINDING CASSETTE TRANSPORTER subfamily G 5 (ABCG5) protein involved in cuticle layer formation. Further investigations reveal that SAV1 interacts with ABCG5, influencing the membrane localisation of ABCG5. Collectively, our results suggest that SAV1 plays a critical role in wax transport by altering the subcellular localisation of ABCG5., (© 2024 John Wiley & Sons Ltd.)

In eukaryotes, the endomembrane system allows for spatiotemporal compartmentation of complicated cellular processes. The plant endomembrane system consists of the endoplasmic reticulum, the Golgi apparatus, the trans-Golgi network, the multivesicular body and the vacuole. Anterograde traffic from the endoplasmic reticulum to the Golgi apparatus is mediated by coat protein complex II (COPII) vesicles. Autophagy, an evolutionarily conserved catabolic process that turns over cellular materials upon nutrient deprivation or in adverse environments, exploits double-membrane autophagosomes to recycle unwanted constituents in the lysosome/vacuole. Accumulating evidence reveals novel functions of plant COPII vesicles in autophagy and their regulation by abiotic stresses. Here, we summarize current knowledge about plant COPII vesicles in endomembrane trafficking and then highlight recent findings showing their distinct roles in modulating the autophagic flux and stress responses., (© 2022 Federation of European Biochemical Societies.)