Differential subcellular distribution and chemical forms of cadmium and copper in Brassica napus

Theodore M Mwamba; Lan Li; Rafaqat A Gill; Faisal Islam; Amir Nawaz; Basharat Ali; Muhammad A Farooq; Jonas L Lwalaba; Weijun Zhou

doi:10.1016/j.ecoenv.2016.08.021

Differential subcellular distribution and chemical forms of cadmium and copper in Brassica napus

Ecotoxicol Environ Saf. 2016 Dec:134P1:239-249. doi: 10.1016/j.ecoenv.2016.08.021. Epub 2016 Sep 15.

Authors

Theodore M Mwamba¹, Lan Li², Rafaqat A Gill², Faisal Islam², Amir Nawaz³, Basharat Ali⁴, Muhammad A Farooq², Jonas L Lwalaba¹, Weijun Zhou⁵

Affiliations

¹ Institute of Crop Science and Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou 310058, China; Faculty of Agriculture, Department of Crop Science, University of Lubumbashi, Lubumbashi 1825, Democratic Republic of the Congo.
² Institute of Crop Science and Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou 310058, China.
³ Institute of Crop Science and Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou 310058, China; Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60000, Pakistan.
⁴ Institute of Crop Science and Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou 310058, China; Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Bonn 53115, Germany.
⁵ Institute of Crop Science and Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou 310058, China. Electronic address: wjzhou@zju.edu.cn.

PMID: 27639199
DOI: 10.1016/j.ecoenv.2016.08.021

Abstract

Metal subcellular fractions and chemical profile highly reflect their level of toxicity to plants. Cadmium and Cu, two different but potentially toxic metals, were compared in the present study for their subcellular distribution and chemical forms in two Brassica napus cultivars (Zheda 622 and ZS 758). Five-week-old seedlings were hydroponically exposed to metal stress and analyzed after 15 days of treatment. In both cultivars, Cd was less retained at cell wall, thus major part of Cd accumulated in the soluble fraction. By contrast, handsome amount of Cu was sequestrated in both cell wall and vacuole containing fraction. Across sensitive organelles, Cu preferentially accumulated in chloroplasts, while Cd was equally distributed in chloroplasts and mitochondria; the two metals intruded nucleus at lesser degree. Further, Cd and Cu differentially interacted with various cellular ligands, and the extent of interaction was higher in the tolerant cultivar ZS 758. Copper was remarkably sequestrated by phosphates, and secondarily by peptide-ligands; inversely, the role of phosphates was secondary in Cd complexation, which was mainly achieved by peptide-ligands. Additional amount of Cu was aggregated with oxalates, but oxalate-bound Cd was scarcely detected. Current results have demonstrated varied toxicological and detoxification pathways of Cd and Cu in B. napus, suggesting that the efficiency of different alleviation strategies could vary against Cd and Cu toxicity to plants.

Keywords: Brassica napus; Cadmium; Copper; Genotypic variation; Intracellular activity.