Metabolite Profiling of Vetiver Grass (Chrysopogon zizanioides) Under Lead Stress.

Lead (Pb) contamination in residential soils and public places due to its prior use in paints and various other household materials is a serious concern in the United States. Children are more prone to Pb toxicity due to ingestion and inhalation. Lead affects nervous and renal systems and also causes behavioral and developmental problems. Phytoremediation is an effective, economically feasible green technology for Pb remediation.  Vetiver (Chrysopogon Zizanioides) is a hyperaccumulator of Pb. Characteristics such as high biomass, an extensive root system and non-invasive nature make vetiver a suitable choice for Pb remediation. Metal stress induces various physiological and biochemical changes in the plant systems. Metabolomic tools can provide an insight into some of these changes, which would lead to a better understanding of the process of metal tolerance and accumulation by hyperaccumulators. Our goal was to identify the global metabolomic changes in the vetiver plants under lead stress.  Plants were subjected to various concentrations (0, 400, 800, 1200 mg/L) of lead for different time periods (0, 10 and 20 days) in a hydroponic set up. Root and shoot samples from all the treatments were analyzed for metabolite changes using GC-MS. Metabolites were extracted in methanol: chloroform: water, then polar and non polar components were separated and derivatized. Raw GC-MS data was deconvulted by Automated Mass Spectral Deconvolution and Identification System (AMDIS) and metabolites were identified using NIST/EPA/NIH Mass Spectral Library - NIST98. Metabolites with significant changes were identified and metabolomic pathway analysis was performed. Salient features of the data obtained show that the major upregulated pathways were tRNA biosynthesis in both root and shoot, amino acid metabolism including glycine, serine, threonine, valine, leucine, isoleucine, arginine and proline in root. The significance of the metabolomic changes in vetiver plant from lead stress will be discussed