The mitochondrial copper chaperone COX19 influences copper and iron homeostasis in arabidopsis

The mitochondrial metallochaperone COX19 influences iron and copper responses highlighting a role of mitochondria in modulating metal homeostasis in Arabidopsis. The mitochondrial copper chaperone COX19 participates in the biogenesis of cytochrome c oxidase (COX) in yeast and humans. In this work, we studied the function of COX19 in Arabidopsis thaliana, using plants with either decreased or increased COX19 levels. A fusion of COX19 to the red fluorescent protein localized to mitochondria in vivo, suggesting that Arabidopsis COX19 is a mitochondrial protein. Silencing of COX19 using an artificial miRNA did not cause changes in COX activity levels or respiration in plants grown under standard conditions. These amiCOX19 plants, however, showed decreased expression of the low-copper responsive miRNA gene MIR398b and an induction of the miR398 target CSD1 relative to wild-type plants. Plants with increased COX19 levels, instead, showed induction of MIR398b and other low-copper responsive genes. In addition, global transcriptional changes in rosettes of amiCOX19 plants resembled those observed under iron deficiency. Phenotypic analysis indicated that the roots of amiCOX19 plants show altered growth responses to copper excess and iron deficiency. COX activity levels and COX-dependent respiration were lower in amiCOX19 plants than in wild-type plants under iron deficiency conditions, suggesting that COX19 function is particularly important for COX assembly under iron deficiency. The results indicate that the mitochondrial copper chaperone COX19 has a role in regulating copper and iron homeostasis and responses in plants.