PROTEOMIC ANALYSIS OF LEAD STRESS-INDUCED CHANGES IN HYDROPONICALLY GROWN VETIVER GRASS (CHRYSOPOGON ZIZANIOIDES L.)

Plants respond to biotic and abiotic stresses through complex biochemical processes. Among abiotic stresses, heavy metal stress is a result of either natural causes or human activities. Lead contamination around residential areas, which resulted from deteriorating lead-based paint used before 1978, is a serious health concern due to the toxic effects of lead on human body, especially in children. Among various remediation methods, phytoremediation is comparatively economical and effective option. Vetiver (Chrysopogon zizanioides), a tropical grass with high biomass, can tolerate and accumulate large quantities of lead in their root and shoot tissues. However, the biochemical mechanisms involved in hyperaccumulation in vetiver are not known. Proteomic changes under lead stress in vetiver can provide a snapshot of biochemical processes involved in metal tolerance and accumulation. In our study, hydroponically-grown vetiver was treated with different concentrations of lead (0, 400, 800, 1200 mg/L). Total protein from shoot and root tissues was extracted separately and analyzed using 2-dimensional gel electrophoresis. Protein spot intensity was measured with ImageMaster 2D platinum (GE healthcare); spots with at least two-fold difference were selected and digested with trypsin. Peptide mass fingerprinting was done using MALDI- TOF/MS (Bruker) and proteins were identified using Mascot database search. Treatments showed differential expression of proteins compared to control plants. Proteins related to photosynthesis, amino acid metabolism and protein phosphatases decreased in treatments. Proteins related to metal transportation, membrane proteins, antioxidative pathway related proteins, sugar transportation and sugar metabolism showed increased expression in treatments. Protein pathways indicating possible mechanisms of metal tolerance and hyperaccumulation will be discussed.