Poster: Late and Moved Abstracts

Abs # 990: Examining the cross resistance of pig mutants to amino acids

Presenter:	Allaire, Erin E, cypripedium@ameritech.net
Authors	Allaire, Erin E (A)   Voll, Lars  (A)   weber, Andreas  (A)
Affiliations:	(A): Michigan State University

The biosynthesis of aromatic, glutamate- and aspartate-derived amino acids are examples of branched pathways. Most of the branching points in these pathways are feedback controlled by the end products. External supply of certain free amino acids leads to feedback inhibition of their respective biosynthetic pathways, and thus has a toxic effect on Arabidopsis thaliana seedlings. We utilized this mechanism to screen for phenylalanine-insensitive (pig) mutants of Arabidopsis. The pig- mutants were isolated from an EMS mutagenized population and are insensitive to at least 10mM Phe, whereas 6 mM Phe is completely toxic to the wild type. Surveying the amino acid contents of pig mutants fed with phenylalanine indicated a cross-resistant effect. Pig mutants were grown on each of the minor amino acids at varying concentrations, and a cross-resistance was evident for some of the amino acids tested, such as most aspartate-derived amino acids, and cysteine. Supplying major amino acids was found to enhance seedling growth for both mutant and wild-type. In addition, toxic effects from minor amino acids could be reverted by adding particular related major amino acids. Our data implies the presence of a ‘general control’ in Arabidopsis. The existence of a ‘general control’ of amino acid metabolism in yeast is well documented. In response to a shortage in one particular amino acid, the ‘general control’ up regulates the biosynthesis of all amino acids. Identification of the PIG gene is currently in progress.