ARS | Publication request: A HIGH-THROUGHPUT GENETIC SCREEN FOR LOW PHYTATE SOYBEANS

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 27, 2004
Publication Date: January 15, 2005
Citation: Chappell, A.S., Bilyeu, K.D. 2005. A high-throughput genetic screen for low phytate soybeans [abstract]. XIII Plant and Animal Genome Conference.

Technical Abstract: Phytate is a phosphorous storage compound widely utilized in plant seeds. Although phytate is a valuable storage compound for plants, the phytate present in crop plants, such as soybeans, poses several health and agricultural problems. Monogastric livestock lack sufficient phytase activity to metabolize the phytate present in soybean feed, leading to inadequate phosphorous uptake. In addition, phytate strongly binds essential minerals such as zinc, calcium and iron, resulting in decreased bioavailability of several additional minerals. These antinutritional factors can be further extended to human health as phytate is considered to be the most important antinutritional factor contributing to the iron deficiency suffered by over 2 billion people worldwide. Thus, the development and characterization of low phytate soybean lines is a high priority in agricultural research. To this end, we are using a reverse genetics approach to identify mutations in phytate biosynthesis genes. Although the exact biochemical pathway for phytate 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 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.