Functional studies of COX17, an Arabidopsis copper chaperone involved in COX biogenesis and stress responses.

GARCIA L., COLOMBATTI F., WELCHEN E, GONZALEZ D.

Rosario

Congreso; ICPMB IV; 2013

COX17 is protein involved in Cytochrome c oxidase (COX) biogenesis providing copper ions for incorporation into COX2 subunit in yeast. We studied the function of COX17-1 (At3g15352) and COX17-2 (At1g66590), two Arabidopsis homologues of yeast copper chaperones using artificial microRNAs to silencing their expression in plants. Copper content is increased in these plants that also show repression of the copper-responsive miR398. We demonstrated that their role in copper metabolism is mediated by SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7). COX17 silenced plants show increased salt stress sensitivity, as evidenced by ROS accumulation, higher lipid peroxidation, altered expression of stress-responsive genes involved in alternative respiratory pathway (AOX1a and NDB2) and lower transcript levels of antioxidant enzymes (CAT, APX, ASO). Because the similar expression pattern of COX17 and AOX1a during different stress condition that we observed, we hypothesize if the role of COX17 under stress could be also mediated by the transcription factor ABSCISIC ACID INSENSITIVE4 (ABI4). Interestingly, COX17 mRNA expression is slightly increased in abi4-1 mutant and is not induced after abscisic acid treatment as wild-type plants. Moreover, Arabidopsis plants over expressing COX17 show increased levels of AOX1a under control condition. Our findings suggest the existence of a link between the role of COX17 during mitochondrial biogenesis and the response to environmental cues in plants.