Objectives The Arabidopsis thaliana ecotype was used to study the adaptive mechanism of root system to cadmium (Cd) stress, providing physiological basis and theoretical guidance for the development of Cd resistance gene and the cultivation of phytoremediation materials.
Methods The Arabidopsis thaliana ecotype Tor-1, with high Cd accumulation and high tolerance to Cd, was used to study the adaptive molecular mechanism of Tor-1 roots to Cd by analyzing the physiological changes, oxidative stress response and antioxidant enzyme activities, combining the transcriptome and alternative splicing analysis.
Results Under Cd treatment, there was no significant difference in the length of main root and number of root tips in Tor-1, while the total root volume and surface area decreased, and the total root length decreased significantly, which all indicated that the roots of Tor-1 were damaged. Compared with the control, the malondialdehyde (MDA) concentration was slightly increased while proline concentration decreased significantly, and superoxide dismutase (SOD) and catalase (CAT) increased significantly under Cd treatment. GO enrichment showed that differential expression genes (DEGs) most significantly enriched in “the metabolic process” and “response to chemical” in the biological process category; in the cell components category, DEGs most significantly enriched in “the extracellular component function”; in the molecular function category, DEGs most significantly enriched in “antioxidant activity” and “heme binding function”. The Kyoto encyclopedia of genes and genomes (KEGG) pathway showed that a high proportion of induced DEGs was enriched in seven KEGG pathways, which were phenylpropanoid biosynthesis (4.49%); biosynthesis of secondary metabolites (14.45%); metabolic pathway (20.57%); glucosinolate biosynthesis (0.89%); glutathione metabolism (2.04%); henylalanine, tyrosine and tryptophan biosynthesis (1.39%); and phenylalanine metabolism (1.14%). Under Cd treatment, the expression of most genes, which were related to phenylpropanoid biosynthesis and metabolism and glutathione (GSH) metabolism, were significantly up-regulated, while the expression of genes related to glucoside (GS) synthesis was inhibited, and alternative splicing was occurred simultaneously in the roots, in which the intron retention events occurred frequently.
Conclusions Although the root morphology of Tor-1 will be damaged under Cd stress, it could still increase antioxidant enzymes (SOD, CAT), and actively reduce the damage of Cd to plants by regulating the biosynthesis and metabolism of phenylpropanoid, glucosinolate biosynthesis and glutathione metabolism, and through alternative splicing to actively adapt to Cd stress.
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