Mitochondrial copper chaperones COX17 and COX19: roles beyond COX assembly.

GARCÍA, LUCILA; COLOMBATTI, FRANCISCO; WELCHEN ELINA; GONZALEZ, DANIEL H.

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB).; 2011

Copper is an essential factor for cytochrome c oxidase (COX) activity. Copper is also required for other cellular functions and is highly toxic when present in excess due to its redox properties. In this work, we studied the function of Arabidopsis COX17-1, COX17-2 and COX19, homologues of yeast copper chaperones involved in COX assembly, using artificial miRNAs to silence their expression in plants. COX2 levels and total dark respiration were similar to wild-type in silenced plants, that did not show morphological or developmental alterations when grown under control conditions but were more sensitive to high salt concentrations and high light. Enhanced stress sensitivity was accompanied by accumulation of reactive oxygen species, higher lipid peroxidation, altered expression of stress-responsive genes, including some of the alternative respiratory pathway (AOX1a and NDB2), and lower transcript levels of antioxidant enzymes (CAT, APX, ASO). In addition, copper content was increased in these plants, that also showed repression of the copper-responsive miR398 and induction of Cu/ZnSOD. Thus, diminished levels of COX17-1, COX17-2 and COX19 are associated with altered copper homeostasis and increased oxidative stress without pleiotropic effects on respiration. These results suggest the existence of a link between mitochondrial function and the response to environmental cues in plants.