Main Molecular Pathways Associated with Copper Tolerance Response in Imperata cylindrica by De Novo Transcriptome Assembly

The metallophyte Imperata cylindrica inhabits copper (Cu) polluted soils in large areas from Central Chile. Here, we subjected clonal vegetative plantlets to 300 mg Cu kg−1 of substrate for 21 days to identify the main molecular pathways involved in the response to Cu stress. Transcriptomic analyses were performed for shoots and roots, with and without Cu supply. RNA-Seq and de novo transcriptome assembly were performed to identify the gene response associated with molecular mechanisms of Cu tolerance in I. cylindrica. De novo transcriptome revealed a total of 200,521 transcripts (1777 bp) comprising ~91% complete ultra-conserved genes in the eukaryote and Plantae database. The differentially expressed genes (DEGs) in roots were 7386, with 3558 of them being up-regulated and the other 3828 down-regulated. The transcriptome response in shoots was significantly less, showing only 13 up-regulated and 23 down-regulated genes. Interestingly, DEGs mainly related with actin and cytoskeleton formation, and to a minor degree, some DEGs associated with metal transporters and superoxide dismutase activity in root tissues were found. These transcriptomic results suggest that cytoskeleton could be acting as a mechanism of Cu-binding in the root, resulting in a high Cu tolerance response in this metallophyte, which deserve to be analyzed ultra-structurally. Our study contributes to reinforcing the potential of I. cylindrica as a candidate plant species to be used as a phytoremediation agent in Cu-contaminated environments.