In vivo phytochelatins and Hg-phytochelatin complexes in Hg-stressed Brassica chinensis L.

In vivo phytochelatins (PCs) and their corresponding Hg-PC complexes were characterized using RPLC-ESI-MS/MS in the roots of Brassica chinensis L. under the stress of a mercury cysteine complex (HgCys(2)) and/or a mercury humic acid complex (Hg-HA). Results indicated that the presence of Cys and/or HA decreased the Hg uptake in both the roots and shoots of B. chinensis but increased the generation of PCs in the roots compared with those where only HgCl2 was in the culture solutions. A series of Hg-PC complexes were synthesized in vitro for predicting the possible Hg-PC formed in vivo in the HgCys(2) and/or Hg-HA stressed roots of B. chinensis. The discovery of in vivo oxidized PC2, PC3 and PC4 and their corresponding HgPC2, HgPC3, HgPC4 and Hg2PC4, which were confirmed by their specific isotope distribution, provided definite evidence for understanding the defense and accumulation mechanism of B. chinensis to Hg, in which the induced PCs play an important role not only in Hg detoxification through forming Hg-PC complexes but also for reducing the oxidative stress induced by Hg2+.