Involvement of Phytochelatins in Lead Accumulation and Tolerance in Vetiver Grass.
Syam S. Andra, Rupali Datta, Dibyendu Sarkar, and Devanand Pachanoor. Univ of Texas, San Antonio, TX 78249
In this study, we investigated whether Vetiver grass (Vetiveria zizanioides L.) can be defined as a "hyperaccumulator” and “non-shoot lead (Pb) excluder" in a hydroponic setting. Furthermore, we simulated the effect of phosphorous (P) phytoavailability of Pb by culturing Vetiver grass in P-and P-free nutrient media. Lead was added to the two nutrient media at concentrations ranging from 400 to 1200 mg/L. After 7 days, we evaluated the Pb uptake, accumulation and root to shoot translocation efficiency in Vetiver- grass. Result indicate that Vetiver grass can tolerate high concentrations of Pb with no toxic physiological effects. Heavy metal tolerance in plants is conferred by Phytochelatins (PCs), a class of post-translational synthetic peptides; which chelate, detoxify, and reduce cellular free metal ion concentrations by forming PC-metal complexes. We studied possible qualitative- and quantitative-differences in PCs between roots and leaves, and between plants grown in P-and P-free nutrient media. Unambiguous characterization of PCs and related forms present in the plant samples was obtained by on-line high pressure liquid chromatography-electrospary ionization mass spectrometry (HPLC-ESI-MS). The collision-induced dissociation (CID) of the selected ions followed by mass spectrometry (MS-MS mode) allowed the determination of the amino acid sequence of each of the PCs, and the detection of the number of Pb ions complexed with the PCs. This study provides evidence of the role of phytochelatins in the tolerance of Pb by Vetiver grass.