Ureide metabolism in response to abiotic stresses in Arabidopsis
Irani, Solmaz 1982-
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Ureides are nitrogenous compounds derived from purine catabolism that contribute to nitrogen recycling in plants. Accumulation of some ureide compounds has been reported in a number of plants under stress conditions, suggesting their involvement in a plant response to stress. Therefore, a biochemical and molecular approach was applied to address the ureide accumulation under drought and increased light intensity stress conditions as well as NaCl and mannitol treatments in Arabidopsis thaliana. Ureide concentration and changes in expression of ureide metabolic genes were examined in response to these stress conditions. Additionally, an Arabidopsis allantoinase (aln) mutant with elevated accumulation of the ureide compound, allantoin, was used to investigate the impact of high levels of this compound on stress response. In the leaf tissue of adult plants allantoin accumulated in response to drought and increased light intensity. Simultaneously, transcription of urate oxidase (UO), involved in allantoin production, was highly up-regulated under stress. Ureides, allantoin and allantoate, also accumulated in seedlings following treatment with NaCl or mannitol. Allantoinase-negative mutants with increased levels of allantoin exhibited higher tolerance to drought and NaCl stresses and growth under high light. Lower level of reactive oxygen species (ROS) accumulated in the allantoinase negative mutant leaves in response to drought compared to the wild-type. Higher concentrations of allantoin in the mutant elevates abiotic stress tolerance, possibly by reducing oxidative damage. These results suggest that ureide metabolism and accumulation contributes to the abiotic stress response which is regulated, at least in part, at the transcript level.
DegreeDoctor of Philosophy (Ph.D.)
CommitteeWei, Yangdou; Bonham-Smith, Peta; Carvolha, Carlos; Gray, Gordon
Copyright DateSeptember 2016
Abiotic stress, Allantoin, Allantoinase, Drought, High light, Salt stress, Ureide