Expression Profiling of the Arabidopsis UCP Gene Family Under Abiotic and Biotic Stress

Mitochondrial uncoupling proteins (UCP) dissipate the proton electrochemical gradient established by the respiratory chain, thus affecting the yield of ATP synthesis. These proteins play a role in maintaining mitochondrial function and are reported to modulate mitochondria-generated reactive oxygen species. In Arabidopsis thaliana, the UCP gene family is composed of three members called AtUCP1-3. In this study, the distinctive expression patterns of these AtUCP genes in response to abiotic and biotic stimuli were investigated using wild-type and Arabidopsis atcup1-3 insertion mutants. The primary purpose was to investigate the existence of functional redundancy between the target genes. According to the results obtained, under normal physiological conditions, a compensatory expression was only observed in the atucp3 mutant, in which the AtUCP1 and AtUCP2 genes were significantly up-regulated. Under salt and osmotic stresses, an early and highly induced expression of AtUCP1 and AtUCP3 was observed in the atucp2 mutant. On the other hand, expression of the target genes did not change significantly in response to biotic stress.  These results suggest that AtUCP3 may serve more general metabolic functions in mitochondria, while AtUCP2 seems to play a role in mitochondrial adaptation to abiotic stress.