Plant mitochondria: Source and target for nitric oxide

• Plant mitochondria generate nitric oxide (NO) under hypoxia and anoxia
• Mitochondrial NO plays a role in plant defence
• Cytochrome c oxidase is a source and target of NO
• NO inhibits aconitase

Plant mitochondria generate nitric oxide (NO) under anoxia through the action of cytochrome c oxidase and other electron transport chain components on nitrite. This reductive mechanism operates under aerobic conditions at high electron transport rates. Indirect evidence also indicates that the oxidative pathway of NO production may be associated with mitochondria. We review the consequences of mitochondrial NO production, including the inhibition of oxygen uptake by cytochrome c oxidase, the inhibition of aconitase and succinate dehydrogenase, the induction of alternative oxidase, and the nitrosylation of several proteins, including glycine decarboxylase. The importance of these events in adaptation to abiotic and biotic stresses is discussed.