Molecular insights into lignin biosynthesis on cadmium tolerance: Morphology, transcriptome and proteome profiling in Salix matsudana

Soil pollution caused by cadmium (Cd) is a serious concern. Phytoremediation is a popular technology in the remediation of Cd-contaminated soil. Salix matsudana var. matsudana f. umbraculifera Rehd. has been charac-terized as a high Cd-accumulating and tolerant willow (HCW). Here, transcriptome and proteome profiling, along with morphology analyses were performed to explore molecular cross-talk involved in Cd tolerance. Our results showed that 73%-83% of the Cd in roots accumulated in the cell walls and root xylem cell walls were significantly thickened. From transcriptome and proteome analysis, a total of 153 up-regulated differentially -expressed genes and 655 up-regulated differentially-expressed proteins were found in common between two comparison groups (1 d and 4 d vs. respective control). Furthermore, phenylpropanoid biosynthesis was iden-tified as a key pathway in response to Cd stress. In this pathway, lignin biosynthesis genes or proteins were significantly up-regulated, and lignin content increased significantly in roots under Cd stress. Two Cd-induced genes cinnamoyl-CoA reductase 1 (SmCCR1) and cinnamyl alcohol dehydrogenase 7 (SmCAD7) from HCW increased the lignin content and enhanced Cd tolerance in transgenic poplar calli. These results lay the foun-dation for further clarifying the molecular mechanisms of Cd tolerance in woody plants.

Automated summary

This study investigated the molecular response of a high cadmium-accumulating and tolerant willow to cadmium stress. Transcriptome and proteome analysis revealed the involvement of the phenylpropanoid biosynthesis pathway and increased lignin content in the roots under cadmium stress. Two cadmium-induced genes from the Willow enhanced cadmium tolerance in transgenic poplar calli.