Electronic Thesis and Dissertation Repository


Master of Science




Dr. Sheila M. Macfie


Phosphoenolpyruvate carboxylase (PEPC) and PEPC kinase (PPCK) catalyze a reaction feeding into the tricarboxylic acid (TCA) cycle, increasing the production of metal-chelating organic acids. Little research has been conducted on PEPC isoenzymes in Cd-stressed plants. Arabidopsis (Arabidopsis thaliana) wild-type and AtPPC1 – AtPPC3 mutants, each lacking one of three PEPC isoenzymes, grown in 0, 1, or 5 µM CdCl2 were smaller and had increased AtPPC1 – AtPPC3 and AtPPCK1 – AtPPCK2 transcript abundance, relative phosphorylation, and PEPC activity, more so in roots than shoots. Concentrations of oxaloacetate, citrate and total organic acids increased with greater CdCl2 concentrations. The absence of AtPPC3, and to a lesser extent AtPPC2, resulted in greater oxaloacetate concentrations and smaller plants in comparison with wild-type. My results indicate that AtPPC3 plays an integral role in Arabidopsis’ ability to cope with Cd. This information can be used to better understand Cd tolerance and stress in other plants, including crops.