Evolution of the endoplasmic reticulum and the Golgi complex.

By analyzing the morpho-physiological features of the Golgi complex, its relationship with the endoplasmic reticulum in different species, and the molecular machineries involved in intracellular transport, we conclude that; (1) all eukaryotic cells have either Golgi complexes or remnants thereof; (2) all eukaryotic cells have a large minimal set of proteins that are involved in intracellular transport; and (3) several indispensable molecular machines are always present in secreting eukaryotic cells. Using this information, our data about mechanisms of intra-Golgi transport and phylogenetic analysis of several molecular machines, we propose a model for the evolution of the Golgi complex and the endoplasmic reticulum.