Ureide metabolism in response to abiotic stresses in Arabidopsis
Date
2016-09-22
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-1560-4857
Type
Thesis
Degree Level
Doctoral
Abstract
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.
Description
Keywords
Abiotic stress, Allantoin, Allantoinase, Drought, High light, Salt stress, Ureide
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Biology
Program
Biology