Phytochemical and Gene Expression Reveals the Antioxidant Responses to Copper Ions in Brassica rapa

The toxicity of increasing heavy metal ion in soil has been threatening the food security and environments. In this study, we used Brassica rapa variety Qinggen #1, a leafy and oil vegetable, to investigate the effects of coper ion (Cu²⁺) on adaptive defense to understand regulatory molecular mechanisms. The variety exhibited a high tolerance at high Cu²⁺ concentration (200 mg L⁻¹). More increases in superoxide radical, hydrogen peroxide, malondialdehyde, and proline were observed at higher concentration than low concentrations. Enzyme activities of SOD, GR, CAT, and APX were significantly altered earlier than corresponding expression of coding genes was up-regulated, indicating two distinct regulations at enzyme and gene levels. The CAT activity and expression correlated with the reactive oxygen species levels, indicating a more important role than other enzymes. Taken together, the high tolerance to Cu²⁺ in B. rapa is resulting from changes in biochemistry, enzyme, and gene expression.