Probing synthesis of L-ascorbic acid in Arabidopsis thaliana genotypes
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L-Ascorbic acid (L-AsA), also known as vitamin C, is a crucial vitamin for both plants and animals due to its antioxidant properties and abilities to scavenge harmful reactive oxygen species (ROS). However, some animals such as humans lost the ability to synthesize their own L-AsA and must therefore fulfill their nutrient requirements via dietary uptake. With increasing global demand for food, studies into methods of increasing L-AsA in crops and determining how environmental stressors can affect the biosynthesis and pool size of L-AsA represent an important and growing field. Herein, quantitative enzymatic UV/Vis measurements and qualitative 13C NMR studies are used with A. thaliana plant tissues to explore biosynthesis of L-AsA. First, studies were done to adapt procedures established within the L-AsA research community for our uses. These experiments resulted in our experimental method of analyzing L-AsA in leaf tissue of leaves 6 -- 13 in 7.5-week-old A. thaliana plants of three genotypes: wt, vtc1-1, and MIOX4. Using this, the L-AsA content of A. thaliana leaves of three genotypes was investigated to provide a baseline for feeding experiments. Then, endogenous L-AsA was measured following individual leaf feeding studies of solutions of L-AsA or its precursors, L-gulono-1,4-lactone (L-GulL) and L-galactono-1,4-lactone (L-GalL), with preliminary tests being done with 13C-labeled L-AsA and L-GulL. Lastly, MIOX4 leaves were discovered to possess elevated L-AsA content beyond a certain developmental stage. This suggests developmental stage as a contributing factor to why certain groups do not see elevated content while others see significant increases.
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Ph. D.