| Mitochondrial gamma-aminobutyrate transaminase (GABA-T) and cytosolic glyoxylate reductase1 (GLYR1) are enzymes associated with stress-activated pathways known as the GABA shunt and photorespiration. This thesis selected and identified one GABA-T overexpressor (OE) and two GLYR1 OE lines of Arabidopsis thaliana, based on both elevated expression of the genes and activity of the resultant enzymes. Metabolic analysis revealed that: (1) the GABA-T OE accumulated less GABA than the wildtype control after exposure to cold stress (4°C) and, (2) the GLYR1 OE modulated the increase in NADPH:NADP+ ratio that characteristically occurred after exposure to atmospheres containing 3% O2 (i.e., hypoxia) or 100 mumol CO2 mol-1 (i.e., enhanced photorespiration). These preliminary findings suggest that overexpression of enzymes for GABA catabolism is a promising strategy for improving flux through the GABA shunt and stress tolerance via maintenance of redox balance. |
