Intracellular localization of VDAC proteins in plants.

Voltage-dependent anion channels (VDACs) are porin-type beta-barrel diffusion pores. They are prominent in the outer membrane of mitochondria and facilitate metabolite exchange between the organelle and the cytosol. Here we studied the subcellular distribution of a plant VDAC-like protein between plastids and mitochondria in green and non-green tissue. Using in vitro studies of dual-import into mitochondria and chloroplasts as well as transient expression of fluorescence-labeled polypeptides, it could be clearly demonstrated that this VDAC isoform targets exclusively to mitochondria and not to plastids. Our results support the idea that plastids evolved a concept of solute exchange with the cytosol different from that of mitochondria.