GENETIC-MODIFICATION OF RESPIRATORY CAPACITY IN POTATO

Mitochondrial respiration was altered in transgenic potato (Solanum tu berosum) lines by overexpression of the alternative oxidase Aox1 gene. Overexpressing lines showed higher levels of Aox1 mRNA, increased lev els of alternative oxidase protein(s), and an unusual higher molecular weight polypeptide, which may be a normal processing/modification int ermediate. Evidence suggests that the alternative oxidase protein is f urther processed/modified beyond removal of the transit peptide. Addit ion of pyruvate to mitochondria oxidizing succinate or NADH increased the alternative pathway capacity but did not eliminate the difference in the capacity between these two substrates. Induction of alternative pathway capacity by aging of tubers appeared to be more dependent on increased levels of alternative oxidase protein than changes in its ox idation state. In leaf and tuber mitochondria, overexpressing lines po ssessed higher alternative pathway capacity than the control line, whi ch suggests that changing the alternative oxidase protein level by gen etic engineering can effectively change alternative pathway capacity.