Comparative Transcriptomics Reveals the Molecular Mechanism Underlying Heavy Metal Detoxification in Aspergillus Niger

<i>Aspergillus niger</i> shows resistance to Zn and Cu; however, limited studies have evaluated the genetic mechanisms underlying metal tolerance in the species. In this study, comparative transcriptome analyses of <i>A. niger</i> F2 under Zn (4000 mg/L) and Cu (3000 mg/L) stress for 15 days were performed to identify genes involved in the response to heavy metal stress. There were more upregulated than downregulated genes under both Cu and Zn stress; however, more genes were differentially expre ssed under Cu than under Zn stress. Downregulated genes under Zn stress were enriched mainly in the membrane part of the cellular component category and for catalytic activity of ribonucleases in the molecular function category. Downregulated genes under Cu stress were enriched for import of Cu ions in the biological process category, intrinsic membrane in the cellula r component category, and reductase and oxidoreductase activity in the molecular function category. Differentially express ed genes under Zn and Cu stress were enriched for different functional domains based on Gene Ontology and Kyoto Ency clopedia of Genes and Genomes analyses. These findings indicated that under heavy metal stress, downregulated genes are mainly involved in ion transport and cell membrane-related functions. Furthermore, energy consumption was higher under Cu stress than under Zn stress, contributing to differences in tolerance levels for A. <i>niger</i>. These findings provide a b asis for genetic engineering for efficient bioremediation.