Living on the edge: the role of Atgolgin-84A at the plant ER–Golgi interface

The plant Golgi apparatus is responsible for the processing of proteins received from the endoplasmic reticulum (ER) and their distribution to multiple destinations within the cell. Golgi matrix components, such as golgins, have been identified and suggested to function as putative tethering factors to mediate the physical connections between Golgi bodies and the ER network. Golgins are proteins anchored to the Golgi membrane by the C‐terminus either through transmembrane domains or interaction with small regulatory GTPases. The golgin N‐terminus contains long coiled‐coil domains, which consist of a number of α‐helices wrapped around each other to form a structure similar to a rope being made from several strands, reaching into the cytoplasm. In animal cells, golgins are also implicated in specific recognition of cargo at the Golgi.Here, we investigate the plant golgin Atgolgin‐84A for its subcellular localization and potential role as a tethering factor at the ER–Golgi interface. For this, fluorescent fusions of Atgolgin‐84A and an Atgolgin‐84A truncation lacking the coiled‐coil domains (Atgolgin‐84AΔ1‐557) were transiently expressed in tobacco leaf epidermal cells and imaged using high‐resolution confocal microscopy. We show that Atgolgin‐84A localizes to a pre‐cis‐Golgi compartment that is also labelled by one of the COPII proteins as well as by the tether protein AtCASP. Upon overexpression of Atgolgin‐84A or its deletion mutant, transport between the ER and Golgi bodies is impaired and cargo proteins are redirected to the vacuole.