Zinc and/or cadmium accumulation in Gynura pseudochina (L.) DC. studied in vitro and the effect on crude protein

Gynura pseudochina (L.) DC. is a zinc (Zn)/cadmium (Cd) hyperaccumulative plant. The aim of this study was to examine the tolerance of G. pseudochina (L.) DC. for Zn and/or Cd accumulation and protein expression. An in vitro tissue culture system was used to control the environment and effects of the microorganisms. Treatments with higher Zn and Cd concentrations increased chlorosis and the accumulation of metals in the root and shoot. Cd treatment at low levels induced the growth of the plant, and the translocation factor was high. A dual treatment with Cd and Zn decreased the metals’ toxicity and demonstrated the plant’s proclivity to accumulate Cd. The SDS–PAGE and FT-IR analyses showed the effect of the metals’ toxicity on protein expression and secondary structure. Moreover, using XAFS techniques, it was demonstrated that treatment with a high Zn concentration (100 mg l−1) resulted in tetrahedral coordination with mixed S/O ligation in the protein extract as compared with ZnO coordination in the protein extract from the control plant cultured in the presence of trace levels of Zn (0.04 mg l−1). This research suggested that G. pseudochina (L.) DC. had properties to tolerate a high Zn and Cd concentration, related to the sulphur proteins.

► Cd/Zn treatment showed competition between Cd and Zn and accumulation of Cd over Zn.
► Cd and/or Zn treatments affected to protein expression and protein structure.
► A high Zn concentration promoted ZnS coordination of cysteine.