Comparative Transcriptome Analysis of the Molecular Mechanism of the Hairy Roots of Brassica campestris L. in Response to Cadmium Stress

Brassica campestris L., a hyperaccumulator of cadmium (Cd), is considered a candidate plant for efficient phytoremediation. The hairy roots of Brassica campestris L are chosen here as a model plant system to investigate the response mechanism of Brassica campestris L. to Cd stress. High-throughput sequencing technology is used to identify genes related to Cd tolerance. A total of 2394 differentially expressed genes (DEGs) are identified by RNA-Seq analysis, among which 1564 genes are up-regulated, and 830 genes are down-regulated. Data from the gene ontology (GO) analysis indicate that DEGs are mainly involved in metabolic processes. Glutathione metabolism, in which glutathione synthetase and glutathione S-transferase are closely related to Cd stress, is identified in the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. A Western blot shows that glutathione synthetase and glutathione S-transferase are involved in Cd tolerance. These results provide a preliminary understanding of the Cd tolerance mechanism of Brassica campestris L. and are, hence, of particular importance to the future development of an efficient phytoremediation process based on hairy root cultures, genetic modification, and the subsequent regeneration of the whole plant.