Do dimers of ATP synthase form the PTP in pea stem mitochondria?

In animal cells Ca2+ and ROS induce a sudden change in the inner mitochondrial membrane permeability, which has been named Permeability Transition (PT). Recently, it has been proposed that dimers of F-ATP synthase form the Permeability Transition Pore (PTP), the megachannel involved in this phenomenon [1]. This feature has not yet been characterized in plants, even if their mitochondria possess the candidate components for PTP formation. Therefore, wecharacterized the functional properties of PTP in plant mitochondria and verified if F-ATP synthase possesses channel function in electrophysiology experiments. Mitochondria isolated from pea stem underwent PT when Ca2+ was added in the presence of the ionophore ETH129. The membrane electrical potential was then collapsed and the phenomenon matched by Ca2+ release but not by mitochondrial swelling. As is observed with the PT of animal mitochondria, Cyclosporin A (CsA) significantly delayed occurrence of PT, which was inhibited by Mg2+-nucleotides and favored by benzodiazepine Bz-423 and oxidants, such as phenylarsine oxide and diamide. In electrophysiology experiments, F-ATP synthase dimers inserted into an artificial bilayer showed channel activity characterized by a rather small conductance, which could explain the inability of plant PTP to mediate mitochondrial swelling. These data suggest that F-ATP synthase is involved in PTP formation also in plant mitochondria.