Schematic representation of models for peroxisome multiplication in S. cerevisiae. The vesicle fusion model proposes all PMPs traffic via the ER and exit in distinct vesicles containing Pex11 and RING finger proteins (Pex2/10/12; green) or docking complex proteins (Pex13/14/17; red). Heterotypic fusion between these vesicles requires the Pex1/6 complex and results in an intermediate compartment (yellow) in which the importomer is fully functional and matrix protein import commences. Peroxisomes form continuously, regardless of whether peroxisomes are already present. According to the growth and division model, preexisting peroxisomes receive newly synthesized membrane and matrix proteins and multiply by DRP-dependent fission. Pex1 and Pex6 are required for matrix protein import by the recycling of the PTS receptors. Only a subset of membrane proteins traffic via the ER (cyan), the remainder being inserted directly into peroxisomes (black). Peroxisomes form de novo only if no peroxisomes are present (reintroduction of peroxisomes): Pex3 localizes first to ER-associated puncta, which subsequently lose ER association (cyan) and acquire other PMPs (yellow), eventually importing matrix (PTS1 containing) proteins (black). Once a cell has formed peroxisomes de novo, they continue to multiply by growth and division.