Recipient Organization
UNIVERSITY OF WISCONSIN SYSTEM
800 ALGOMA BLVD
OSHKOSH,WI 54901-8601
Performing Department
(N/A)
Non Technical Summary
Many plant species form calcium oxalate crystals within edible tissues. The functions of these crystals are many-fold, and may include calcium regulation and protection from herbivores. An unfortunate side effect of this widespread biochemical process is the accumulation of oxalic acid, a toxin in both humans and animals, in many important crop and forage plants. Our knowledge of how plants make oxalic acid is limited; therefore, strategies designed to decrease levels of oxalic acid in plants have been hampered. The goal of this project is to examine the biosynthesis of oxalic acid in several common crop plants (consumed by humans), and in addition several forage plants, some grown as feed for farm animals, others that are encountered by farm animals grazing on non-cultivated land. The first step in dissecting the biosynthesis of oxalic acid will be determining what chemical substance is converted into oxalic acid in these plants. Preliminary evidence suggests that this
substance is ascorbic acid (vitamin C). If this is found to be true, the second step will be to find out how ascorbic acid is converted to oxalic acid within the plant. The information gathered from this study will then be used to develop strategies designed to decrease levels of oxalic acid in crop and forage species, and thus decrease the health risks this toxin poses. The ultimate goal is to increase the safety of some foods, and decrease agricultural losses associated with ingestion of high-oxalic acid containing plants by foraging farm animals.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Proposal number 2002-03483 The objectives of this project are to determine if ascorbic acid (AsA) is the primary precursor of oxalic acid (OxA) in selected crop and forage plant species. The second goal, once objective number one is achieved, is to determine how AsA is biochemically converted to OxA in these plants. The information gathered can then be used in developing strategies designed at reducing the amounts of potentially toxic OxA in these agronomically important plants.
Project Methods
Proposal number 2002-03483 Determining if ascorbic acid is the primary precursor of oxalic acid in crop and forage plants will utilize three different approaches. First, leaf material will be fed 1-[14C] Ascorbic acid, embedded in plastic, sectioned, and examined using microautoradiography for incorporation of ascorbic acid into calcium oxalate crystals. Second, soluble and insoluble oxalic acid and ascorbic acids levels will be monitored using HPLC and Liquid Scintillation Counting to follow conversion of ascorbic acid into oxalic acid. Third, key enzyme in the biosynthesis of ascorbic acid in plants, 1,4, galactono-g -lactone, will be localized at the light and electron microscopy levels to gather further evidence for the role of ascorbic acid in oxalic acid synthesis. If it is determined that ascorbic acid is the primary precursor of oxalic acid, tissues of the selected species will be fed non-labeled ascorbic acid analogs in addition to labeled ascorbic acid. Again,
incorporation of label into oxalic acid will be monitored via HPLC, Liquid Scintillation Counting, and microautoradiography. In addition to ascorbic acid, levels of dehydroascorbic acid, peroxydehydroascorbic acid, and glutathione will be examined to gather evidence for a possible conversion pathway.