UREIDE ACCUMULATION DURING ABIOTIC STRESS IN LEGUMES

Abstract

Allantoin and allantoate, ureides formed during the catabolism of purines, accumulate in plant tissue in response to drought and other abiotic stresses. Allantoin, allantoate, and a precursor molecule, uric acid, have been hypothesized to be scavengers of the reactive oxygen species (ROS) formed during abiotic stress. This research investigated whether a direct link exists between these ureides and the ROS produced during water limitation, sub-zero temperature stress, and induced oxidative stress. Allantoin and allantoate accumulated in both nitrogen-fixing and nitrogen-fertilized soybean leaves during water limitation. The accumulation of ureides in the leaves could also be generated by treatment with methyl viologen (MV) which induces superoxide production. Isolated leaf disk experiments demonstrated that allantoin did not directly scavenge ROS, but stimulated a response in the plant that indirectly decreased ROS. In contrast, uric acid had a direct chemical interaction with hydrogen peroxide (H2O2). Both allantoin and uric acid decreased cell death in leaf tissue after treatment with H2O2 and allantoin decreased cell death after treatment with MV. In addition, I examined whether the accumulation of ureides could be used to predict abiotic stress tolerance of different genotypes in a population of common bean, tepary bean and interspecific introgression lines of common bean and tepary bean. Sub-zero temperature stress and water limitation stress tolerance were correlated with ureide content in a population of common bean, tepary bean and interspecific introgression lines of common bean and tepary bean, however these correlations were too weak for implementation of ureide accumulation quantification as a plant breeding tool. Results of this thesis will aid in understanding ureide accumulation during abiotic stress, will assist in determining the function of ureide accumulation during abiotic stress, and will serve as the starting point to bridge the gap between the mechanistic knowledge of ureide accumulation during abiotic stress and applying it in larger scale agricultural scenarios.