Submitted to: American Society of Plant Biologists
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2005
Publication Date: 3/11/2005
Citation: Chappell, A.S., Bilyeu, K.D. 2005. A high-throughput molecular screen for low phytate soybeans [abstract]. American Society of Plant Biologists Annual Meeting.
Technical Abstract: Phytic acid is a phosphorous storage compound widely utilized in plant seeds, including crop plant seeds such as soybeans. Phytic acid is often found as a mixed salt called phytate that comprises phytic acid bound to positively charged cations such as zinc, iron and magnesium. Phytate accounts for approximately 75% of the total seed phosphorous in soybean and 1% of the total seed dry weight. Monogastric livestock lack sufficient enzyme activity to metabolize the phytate present in soybean feed, leading to inadequate phosphorous uptake. Furthermore, the strong chelating property of phytic acid prevents the absorption of important minerals, leading to their decreased bioavailability. These antinutritional factors of phytic acid can be further extended to human health as phytic acid is considered to be the most important antinutritional factor contributing to the iron deficiency suffered by over 2 billion people worldwide. These antinutritional properties make the development and characterization of low phytate soybean lines a high priority in agricultural research. To this end, we are using a reverse genetics approach to identify mutations in known phytic acid biosynthesis genes. Although the exact biochemical pathway for phytic acid biosynthesis in soybean is not known, several key enzymes have been identified in various plant species. One such enzyme, inositol trisphosphate kinase (Itpk), has been identified in several plants including Arabidopsis and maize. We have identified three soybean ITPK genes based on homology to the Arabidopsis and maize genes. Using quantitative real-time RT-PCR, we found that one of the three ITPK genes (ITPK3) is highly expressed in developing seeds. This gene is now the subject of TILLING (Targeting Induced Local Lesions IN Genomes), a high-throughput molecular assay used to detect mutations in target genes from a large set of mutated individuals.