Metabolic response of vetiver grass (Chrysopogon zizanioides) to acid mine drainage

Acid mine drainage (AMD) is a sulfuric discharge containing metals and particulates that can spread to nearby water sources, imposing toxicity and physical stress to living things. We have shown that vetiver grass (Chrysopogon zizanioides) is capable of tolerating and treating AMD-impacted water from the abandoned Tab-Simco mining site from southern Illinois, though little is known about its tolerance mechanisms. We conducted metabolomic analyses of vetiver shoots and roots after relatively short- and long-term periods of exposure to Tab-Simco AMD. The metabolic shift of vetiver shoots was dramatic with longer-term AMD exposure, including upregulation of amino acid and glutathione metabolism, cellular respiration and photosynthesis pathways, with downregulation of phosphorylated metabolites. Meanwhile, the roots demonstrated drastic downregulation of phospholipids and phosphorylated metabolites, cellular respiration, glyoxylate metabolism, and amino acid metabolism. Vetiver accumulated ornithine and oxaloacetate in the shoots, which could function for nitrogen storage and various intracellular functions, respectively. Organic acids and glutathione were secreted from the roots for rhizospheric metal-chelation, whereas phosphorylated metabolites were recycled for phosphorus. These findings reveal AMD-induced metabolic shifts in vetiver grass, which are seemingly unique in comparison to independent abiotic stresses reported previously.