BIOCHEMICAL AND GENETIC-CONTROLS EXERTED BY PLANT-MITOCHONDRIA

Higher plant mitochondria contain two terminal oxidases, cytochrome c oxidase and a cyanide-resistant 'alternative' oxidase. Electron flux t hrough these two respiratory pathways is controlled by environmental c onditions, stimuli received by mitochondria. In general, stresses such as cold, wounding, pathogen attack and others favor electron flow thr ough the alternative oxidase. One of the proposed functions of the alt ernative pathway is to relieve the tricarboxylic acid (TCA) cycle of i nhibition from cytochrome pathway products and allow the cycle to furn ish carbon skeletons for anabolic requirements. We are currently inves tigating, with an NADP-linked isocitrate dehydrogenase in plant mitoch ondria, a possible link between respiratory control and carbon flux fr om the TCA cycle. Regulation of the nuclear gene encoding the alternat ive oxidase, Aox1, is also being employed as a model for perception of the many stresses by the mitochondria and transfer of these signals t o the nucleus. Our initial results indicate that hydrogen peroxide is an intermediate in this signalling process. (C) 1998 Elsevier Science B.V.