Copper toxicity affects indolic glucosinolates and gene expression of key enzymes for their biosynthesis in Chinese cabbage

ABSTRACT

Excessive levels of Cu²⁺ are phytotoxic and exposure of Chinese cabbage to elevated Cu²⁺ concentrations led to reduction of the plant biomass. To get more insight into the role of glucosinolates upon copper stress, the impact of elevated Cu²⁺ levels on glucosinolates biosynthesis were studied in Chinese cabbage. The content of total glucosinolates was only elevated in the roots, mostly due to indolic and aromatic glucosinolates. The results showed a higher contribution of indolic glucosinolates, notably glucobrassicin, a 2- and 4-fold increase in Chinese cabbage exposed to 5 and 10 µM Cu²⁺, respectively. Furthermore, the increase in the indolic glucosinolates was accompanied by enhanced transcript levels of CYP79B2 and CYP83B1, two genes involved in biosynthesis of indolic glucosinolates, and that of the MYB51, a transcription factor involved in regulation of indolic glucosinolate biosynthesis pathway, at elevated Cu²⁺ concentrations. In addition, total sulfur and nitrogen remained unaffected in the root, but total glucosinolate was significantly enhanced upon exposure to elevated Cu²⁺. This result may show that relatively more sulfur and nitrogen was channeled into glucosinolates in the root. In conclusion, accumulation of indolic glucosinolates in the root can be considered as a strategy for Chinese cabbage to combat elevated Cu²⁺ concentrations.

KEYWORDS:

• Chinese cabbage
• copper
• gene expression
• indolic glucosinolate
• sulfur metabolism

Acknowledgements

Financial support was provided by the Danish National Research Foundation DNRF grant 99 (MB). The authors wish to thank Dr. Luit De Kok for his supports in the laboratory of plant physiology, University of Groningen.

Disclosure statement

We declare that we have no conflict of interest.

Additional information

Funding

This work was supported by the Danish National Research Foundation DNRF grant [99] 99 (MB).