Model for the role of the Atg9 reservoirs in double-membrane vesicle formation. The Atg9 reservoirs, which often are adjacent to mitochondria, act as a pre-PAS. Association with the prApe1 oligomer in nutrient-rich conditions (Cvt pathway) and probably cellular signals during starvation (autophagy) induces the translocation of one or more Atg9 reservoirs into close proximity with the vacuole. This relocalization event triggers the recruitment of the rest of the Atg proteins to a reservoir, leading to the formation of the PAS. Successive fusion of the tubulovesicular membranes composing the PAS and possibly acquisition of additional membrane from other Atg9 reservoirs and/or other sources creates a double-membrane vesicle.