Metabolite Profiling of Induced Mutants of Rice and Soybean

The low phytic acid (lpa) rice (Os-lpa-XS110-1, Os-lpa-XS110-2) and soybean (Gm-lpa-TW-75-1, Gm-lpa-ZC-2) mutants generated by γ-irradiation were studied, aimed at comparing these mutants to the corresponding wild-types by means of metabolite profiling based on capillary gas chromatography/mass spectrometry. The usefulness of this approach to assist in the elucidation of the types of mutation resulting in reduced contents of phytic acid should be explored. Metabolite profiling aspires to provide a comprehensive picture of the metabolites present in biological systems. It aims at extracting, detecting, identifying, and quantifying a broad spectrum of compounds in a single sample, to provide a deeper insight into complex biological systems. The extraction and fractionation method used allowed a comprehensive coverage of a broad spectrum of low molecular weight metabolites ranging from lipophilic (fatty acids methyl esters, hydrocarbons, free fatty acids, sterols, tocopherols) to hydrophilic (sugars, sugar alcohols, organic acids, amino acids) compounds. For rice, considerable amounts of the peaks detected were statistically significantly different between wild-types and lpa mutants grown in the same field trial. However, only a few of these differences could be consistently observed in all analyzed field trials, indicating a strong influence of the biological variability. Metabolites consistently shown to be significantly different between wild-type and lpa rice mutants, were found to be closely related to the biogenetic pathways leading to phytic acid. This allowed a prediction of the mutation targets for the lpa rice mutants in the biosynthetic pathway of phytic acid. Similar effects, i.e. statistically significantly different levels of metabolites closely related to the biosynthesis of phytic acid, were consistently observed for soybean. (author)