Metabolomics analysis reveals different mechanisms of cadmium response and functions of reduced glutathione in cadmium detoxification in the Chinese cabbage

Chinese cabbage (Brassica rapa) is one of the vegetable crops with the largest acreage and yield in East Asia. With the aggravation of heavy metal pollution in soil, the excessive accumulation of heavy metal has become increasingly severe in Chinese cabbage, among which, cadmium is one of the most representative elements. It is critical to understand the regulatory mechanism of Cadmium (Cd) response and tolerance in Chinese cabbage at the metabolism level. Comparative of functional metabolomics and transcript analyses were conducted in Chinese cabbage grown on half-strength MS solid medium with different Cd concentrations (5, 25, 100 µM Cd). The results revealed that the transcript responses were not consistent with the metabolic responses, and Cd treatment at different concentrations could induce more specific differentially expressed metabolites. Moreover, the reduced glutathione (GSH) metabolism pathway was induced under the higher Cd stresses (25, 100 µM Cd). The following result indicated that the GSH played a role in the reduction of Cd accumulation in Chinese cabbage under the higher Cd stresses but led to Cd accumulation under the low Cd stress. This study offers critical information on handling Cd contamination in Chinese cabbages at the different Cd contamination conditions. Different concentration of Cd stresses resulted different responses in Chinese cabbage, and GSH accumulate Cd in the low Cd stress, and exclude Cd in the higher Cd stresses in Chinese cabbage.