The retargeting of proteins to the peroxisome during evolution. The dashed lines indicate the ancestral cellular location of a peroxisomal protein, the continuous line their current (peroxisomal) location. Some proteins are derived from the alpha-proteobacterial ancestor of the mitochondria, their proteins have been retargeted to the peroxisome concomitant with the transfer of their genes to the nucleus (red, scenario I). Also proteins without a (detectable) alpha-proteobacterial ancestry have been retargeted from the mitochondria (blue, scenario II). Finally, a class of proteins have been retargeted from other compartments of the cell like the Endoplasmic Reticulum (cyan, scenario III).