Poster: Mineral nutrition

Abs # 204: Phytic Acid Utilization by Arabidopsis as a Source of Phosphorus

Presenter:	Ward, James T., wardj@purdue.edu
Authors	Ward, James T. (A)   Karthikeyan, A. S. (A)   Poling, Mike  (A)   Raghothama, Kaschandra G. (A)
Affiliations:	(A): Department of Horticulture and Landscape Architecture Purdue University
Web Site:	http://www.hort.purdue.edu

Phytic acid, one of the major forms of phosphorus in manures and organic soils, is a potentially valuable source of this essential plant nutrient. However, most crop species poorly utilize phytic acid. Further, soils containing large quantities of phytic acid, like those used for manure disposal, contribute to pollution and the eutrophication of aquatic ecosystems. To study the utilization of phytic acid by plants, we evaluated the ability of Arabidopsis to grow on media containing phytic acid as the sole source of phosphorus. Our studies show that Arabidopsis plants grown on phytic acid appear healthy and similar to plants grown with orthophosphate during their first few weeks of growth. However, they do have a pronounced elongated root phenotype and altered phosphatase activity. The expression of a number of genes normally induced under phosphorus starvation, including AtPT2, a high affinity phosphate transporter, and a number of phosphatases, was not up-regulated, confirming that phytic acid was serving as a ready source of phosphate. Similarly, a luciferase reporter gene under the regulation of a phosphorus starvation induced gene promoter was also not up-regulated. Using these results we developed a novel screen of populations of mutagenized Arabidopsis plants that express the reporter gene. Through this screen we have identified a number of putative mutants with altered luciferase gene expression and morphology when they are grown on phytic acid. We are currently characterizing the mutants and cloning the mutated gene(s) responsible for the altered phenotype. Our results suggest that phytic acid can be used as a valuable screening tool for the identification of mutants altered in phosphorus uptake and in the regulation of phosphorus deficiency mediated processes.