Title: Phytic Acid Metabolism in Plants

Speaker: Dr. Sang-Ic Kim

USDA-ARS, Crops Pathology/Genetics Research Unit University of California, Davis

Phytic acid is the primary storage form of phosphorus (P) in seeds where it is found in the form of a mixed salt (phytate) and accounts for 65-80% of the total seed P. During germination, seed phytases break down phytate into its constituents (myo-inositol, inorganic P, and mineral cations) which are mobilized to support seedling growth and development. Phytic acid cannot be digested by non-ruminant livestock or human beings who are thus unable to utilize the majority of the P in seeds. At physiological pH, the negatively charged phosphate groups of phytic acid strongly chelate mineral cations thereby reducing the bioavailability of these important micronutrients. Given these attributes, seed phytic acid is considered an anti-nutrient and lowering phytate is one important strategy for increasing the nutritional and economic value of seed crops. To understand the biosynthesis and accumulation of phytic acid in seeds,

our lab has employed both forward and reverse genetics. The main focus of my research has been the isolation of the rice low phytic acid (lpa) gene, which was identified by forward genetics. Rice lpa1 mutants exhibit a 45-50% reduction in phytic acid with a corresponding

increase in inorganic P which maintains the overall seed P content. Using a map-base cloning approach, we cloned the rice lpa1 gene which encodes a novel protein. The functional characterization of this gene will be discussed. In addition to rice lpa1, I have also pursued the identification of other genes involved in phytic acid metabolism which has resulted in the

cloning of the rice myo-inositol kinase gene using a forward genetics strategy and am also exploiting the reverse genetics method TILLING in rice to examine other genes potentially involved seed phytic acid biosynthesis. Identifying and characterizing lpa mutant genes provides a foundation for elucidating the contributions of different biosynthetic pathways and for

developing strategies to engineer seed crops with increased nutritional value.  

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Title: Genetic mechanism of hybrid incompatibility

Speaker: Dr. Eunyoung Chae

Department of Molecular Biology

Max Planck Institute for Developmental Biology Germany

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Title: Differential plastic responses or local adaptations Insights from natural phenotyping

Speaker: Dr. Sang-Tae Kim

Department of Molecular Biology

Max Planck Institute for Developmental Biology Germany