Chelator profiling in Deschampsia cespitosa (L.) Beauv. Reveals a Ni reaction, which is distinct from the ABA and cytokinin associated response to Cd.

Plant hormones, including abscisic acid (ABA) and cytokinins (CKs), fluctuate as a result of excess metal exposure. Changes in hormonal concentration regulate plant growth and may also signal activation of metal chelators. The grass Deschampsia cespitosa was dosed with either Ni or Cd or pulsed with exogenous ABA. The roots were analyzed for ABA and CKs and for multiple potential metal chelators including: amino acids, nicotianamine (NA), and phytochelatins (PCs). They were quantified after 3 h and after 7 days, using LC-ESI MS/MS. The Ni treatment caused no measurable change in ABA or CK concentration; however, an increase in NA was documented. The Cd treatment resulted in a short-term ABA increase followed by a reduction in CKs and an increase in PC concentration. An exogenous ABA pulse in non-metal challenged plants induced changes in CKs and PCs that followed those of Cd treatment. Ni and Cd stress resulted in distinctly different detoxification responses. Since the reaction of CKs and putative metal chelators to Cd stress can be mimicked by an exogenous ABA pulse, it is suggested that ABA acts as a stress signal, resulting in reduced growth by way of decreased CK concentration and reduced metal toxicity through increased PC production.

Identification and quantification of glutathione and phytochelatins from Chlorella vulgaris by RP-HPLC ESI-MS/MS and oxygen-free extraction.

Phytochelatins are short, cysteine-containing, detoxification peptides produced by plants, algae, and fungi in response to heavy metal exposure. These peptides auto-oxidize easily. Current extraction protocols do not adequately address losses of phytochelatins because of their oxidation and the use of indirect methods for quantification. Method enhancements include the use of an argon environment during extraction to reduce auto-oxidation, the use of glycine-(13)C2-labeled glutathione as an internal standard, and an electrospray ionization source with a triple quadrupole mass spectrometer as a detector. The method-detection limits were 0.081 microM for glutathione, 0.440 microM for phytochelatin 2, and 0.120 microM for phytochelatin 3. These detection limits were comparable to similar studies and were not compromised incorporating these adjustments. The use of a labeled internal standard and an inert gaseous environment during sample preparation greatly improved calibration linearity and sensitivity. Furthermore, phytochelatin degradation was significantly reduced and more accurately tracked. Previous studies involving phytochelatin analyses have likely been subject to higher variability caused by this propensity for phytochelatins to degrade rapidly in air. The method adjustments were simple and cost-effective and allowed phytochelatin analyses to be performed for hours at a time with minimal auto-oxidation.