Research Projects

Alternative oxidase (AOX) is a mitochondrial enzyme that is induced in plants under various abiotic stress conditions. The plant mitochondrial oxidative electron transport bifurcates into the cyanide sensitive cytochrome oxidase (COX) pathway and the cyanide resistant and salicylhydroxamic acid (SHAM) sensitive AOX pathway. The AOX pathway activates upon restriction of the COX pathway, and the total flux of electrons towards the AOX pathway increases under various abiotic stress conditions. Preliminary results with salt stress-sensitive Arabidopsis thaliana and salt stress-tolerant Eutrema salsugineum plants have indicated differential expression of AOX isoforms under salt stress conditions. AOX1a, the most abundant isoform observed in leaves of both species, is induced during salt/drought stress in salt stress-sensitive A. thaliana plants, while constitutive expression is observed in salt stress-tolerant E. salsugineum plants. The functional characterization of the AOX1a protein from salt stress-sensitive A. thaliana and salt stress-tolerant E. salsugineum plants will be performed using a reverse genetics approach. The AOX1a will be heterologously expressed in a simpler eukaryotic model system, Saccharomyces cerevisiae, to understand differences in regulation and their role in oxidative stress alleviation. Protein carbonylation will be used as a marker for studying cellular oxidative stress, and comparative analysis of interacting proteins of wild-type AOX1a and mutants in both salt-sensitive A. thaliana and salt-tolerant E. salsugineum will provide novel insights about the differential regulation of AOX in salt-sensitive and tolerant plants.