Comparative Metabolomic Profiling Of Vetiver (Chrysopogon zizanioides) and Maize (Zea mays) Under Lead Stress.

Lead is ranked as the second most toxic heavy metal, which was widely used in paint, gasoline, pipes, solders, ceramics, batteries etc. The most common source of lead exposure in the U.S. currently is lead paint contaminated older homes, where yard soil and house dust is contaminated with lead. Phytoremediation is an effective and eco-friendly technology to combat high blood lead levels through ingestion and inhalation, especially in children. Our group has demonstrated the lead hyperaccumulation capability of Chrysopogon zizanioides, a high biomass, semi-tropical grass. Plant adaptations to the immediate surroundings, e.g. metal stress, are reflected on various metabolic pathways.  Metabolomic and proteomic tools can provide insights into some of biochemical and physiological adaptations in plants under lead stress. Deciphering these adaptations can lead to a better understanding of the process of metal accumulation and tolerance in accumulator plants. Our objective was to study the metabolic changes in the accumulator plant, vetiver grass in comparison to a closely related grass, maize, grown hydroponically in various lead concentrations; i.e., 0, 400, 800 and 1200 mg/L in a hydroponic set up for different time periods. Quantitative metabolomic profiling was performed using 5500 QTRAP (LC/MS/MS) hybrid triple quadrupole mass spectrometer. The mass spectrometer was run using MRM mode with positive/negative polarity switching. Approximately 300 metabolites were targeted. Metabolites with significant changes were identified and metabolomic pathway analysis was performed. The major up-regulated pathways were tRNA biosynthesis in root and shoot, amino acid metabolism including glycine, serine, threonine, valine, leucine, isoleucine, arginine and proline in root. Significant differences in metabolic changes between the two species will be presented.