title: Analysis of phytochelatin complexes in the lead tolerant vetiver grass [Vetiveria zizanioides (L.)] using liquid chromatography and mass spectrometry.
abstract: Ethylenediamene tetraacetic acid (EDTA) has been used to mobilize soil lead (Pb) and enhance plant uptake for phytoremediation. Chelant bound Pb is considered less toxic compared to free Pb ions and hence might induce less stress on plants. Characterization of possible Pb complexes with phytochelatins (PCn, metal-binding peptides) and EDTA in plant tissues will enhance our understanding of Pb tolerance mechanisms. In a previous study, we showed that vetiver grass (Vetiveria zizanioides L.) can accumulate up to 19,800 and 3350 mg Pb kg(-1) dry weight in root and shoot tissues, respectively; in a hydroponics set-up. Following the basic incubation study, a greenhouse experiment was conducted to elucidate the efficiency of vetiver grass (with or without EDTA) in remediating Pb-contaminated soils from actual residential sites where Pb-based paints were used. The levels of total thiols, PCn, and catalase (an antioxidant enzyme) were measured in vetiver root and shoot following chelant-assisted phytostabilization. In the presence of 15 mM kg (-1) EDTA, vetiver accumulated 4460 and 480 mg Pb kg(-1) dry root and shoot tissue, respectively; that are 15- and 24-fold higher compared to those in untreated controls. Despite higher Pb concentrations in the plant tissues, the amount of total thiols and catalase activity in EDTA treated vetiver tissues was comparable to chelant unamended controls, indicating lowered Pb toxicity by chelation with EDTA. The identification of glutathione (referred as PC1) (m/z 308.2), along with chelated complexes like Pb-EDTA (m/z 498.8) and PC(1)-Pb-EDTA (m/z 805.3) in vetiver root tissue using electrospray tandem mass spectrometry (ES-MS) highlights the possible role of such species towards Pb tolerance in vetiver grass.
authors.affiliation: Environmental Geochemistry Laboratory, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, USA. syam.andra@gmail.com
authors.forename: Syam S
authors.initials: SS
authors.lastname: Andra
authors.forename: Rupali
authors.initials: R
authors.lastname: Datta
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Sarkar
authors.forename: Sumathi K M
authors.initials: SK
authors.lastname: Saminathan
authors.forename: Conor P
authors.initials: CP
authors.lastname: Mullens
authors.forename: Stephan B H
authors.initials: SB
authors.lastname: Bach
mesh_terms: D015142:Baltimore; D001673:Biodegradation, Environmental; D002374:Catalase / Q000032:analysis; D002614:Chelating Agents / Q000494:pharmacology; D002853:Chromatography, Liquid; D049930:Chrysopogon / Q000737:chemistry* / Q000378:metabolism; D002947:Cities; D004492:Edetic Acid / Q000494:pharmacology; D018527:Hydroponics; D007220:Industrial Waste / Q000032:analysis; D007854:Lead / Q000032:analysis; D054811:Phytochelatins / Q000302:isolation & purification*; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism; D018520:Plant Shoots / Q000737:chemistry / Q000378:metabolism; D012989:Soil Pollutants / Q000032:analysis; D013438:Sulfhydryl Compounds / Q000032:analysis; D053719:Tandem Mass Spectrometry / Q000379:methods; D013781:Texas
chemical_list: D002614:Chelating Agents; D007220:Industrial Waste; D012989:Soil Pollutants; D013438:Sulfhydryl Compounds; D007854:Lead; D054811:Phytochelatins; D004492:Edetic Acid; D002374:Catalase