Lignin Biosynthesis Plays an Important Role on Cadmium Tolerance in Salix Matsudana VAR. Matsudana F. Umbraculifera Rehd

Recently, the soil pollution caused by Cd is becoming a serious concern . Phytoremediation is the popular technology in the remediation of Cd contaminated soil. Salix matsudana var. matsudana f. umbraculifera Rehd. has been characterized as a high cadmium-accumulating and tolerant willow, but molecular and physiological mechanisms underlying tolerance are poorly comprehended. Here, our results showed that Cd was mainly accumulated in the cell walls, and chemical components of cell wall were involved in Cd complexation by FTIR analysis . Data from transmission electron micrographs exhibited a significant thickening in root xylem cell walls. A total of 153 common up-regulated different expression genes and 655 common up-regulated different expression proteins were identified from RNA-seq and TMT (Tandem Mass Tag) sequencing, and GO terms were found to be related to transporter activity, ion binding, as well as cinnamyl-alcohol dehydrogenase activity. Furthermore, phenylpropanoid biosynthesis was identified as a key pathway by integrated transcriptomic and proteomic analysis. Lignin biosynthesis genes or proteins were significantly up-regulated, and lignin content increased significantly in roots under Cd stress. These results will lay the foundation for further clarifying the molecular mechanisms of Cd tolerance in woody plants and provide valuable ways on phytoremediation of Cd pollution