Rapid effect of cadmium on lignin biosynthesis in soybean roots

Abstract The significant root inhibition growth in Cd-treated soybean ( Glycine max ) seedlings correlated with the increase of H 2 O 2 levels, peroxidases and laccases activity. The increased peroxidase activity might remove excess H 2 O 2 as the incubation was prolonged during Cd treatment, thus playing a detoxifying role. The increase of the activities of peroxidase (p I 8.8, p I 7.7, p I 5.2, p I 4.5, p I 4.4, and p I 3.7) and laccase (p I 9.2, p I 8.9, p I 8.3, p I 5.4, p I 4.2, and p I 3.7) were accompanied by the rise of lignin contents in Cd-treated tissues. In Cd-treated root tips, transcript levels of POXs (p I 7.7, p I 5.2, p I 4.5, p I 4.4, and p I 3.7 POXs) increased significantly compared with the controls after 48 h of treatment. Our results suggest that laccases are responsible for lignin biosynthesis during the early stage of Cd treatment. Laccases and peroxidases worked cooperatively in lignin synthesis when the treatment was prolonged.