Presence of the ER-Golgi intermediate compartment that matures into the Golgi in yeast

Cargo traffic through the Golgi apparatus is mediated by cisternal maturation, but it remains largely unclear how the cis -cisternae, the earliest Golgi sub-compartment, is generated. Here, we use high-speed, high-resolution confocal microscopy to analyze the spatiotemporal dynamics of a diverse set of proteins that reside in and around the Golgi in budding yeast. We find many mobile punctate structures that harbor yeast counterparts of mammalian endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC) proteins, which we term “yeast ERGIC”. It occasionally attaches onto the ER exit sites and gradually matures into the cis -Golgi. Upon treatment with the Golgi-disrupting agent brefeldin A, the ERGIC proteins form larger aggregates corresponding to the Golgi entry core compartment in plants, while cis - and medial-Golgi proteins are absorbed into the ER. We further analyze the dynamics of several late Golgi proteins. Together with our previous studies, we demonstrate a detailed spatiotemporal profile of the cisternal maturation process from ERGIC to Golgi and further to the trans -Golgi network.