Transcriptome analysis reveals the mechanism of tolerance to copper toxicity in the white rot fungus Trametes hirsuta AH28-2

Heavy metals, such as copper (Cu), are prevalent in the environment and pose a substantial threat to human health. White rot fungi, especially Trametes spp., display prominent Cu tolerance and removal capacity. However, how Trametes responds to environmental Cu stress remains poorly understood. Here, we found that Trametes hirsuta AH28-2 exhibits Cu removal efficiencies varying from 80.8 % at 1.25 mg/L to 57.6 % at 37 mg/L. Comparative transcriptome analysis identified 812, 1898, and 2110 differentially expressed genes (DEGs) at the Cu concentrations of 1.25, 12.5, and 25 mg/L, respectively. Some DEGs were associated with antioxidant defense systems, secondary metabolite biosynthesis (terpenoids and polyketides), transmembrane transport, and glutathione metabolism, potentially enhancing Cu tolerance. The activities of antioxidant enzymes such as superoxide dismutase, catalase, and laccase were increased under Cu stress. qRT-PCR confirmed the alterations in gene expression and demonstrated that glutathione S-transferases, catalases, cytochrome P450s, and laccases were involved in counteracting Cu-induced stress. Gene silencing experiments further confirmed the crucial roles of laccases in this process. Many transcription factors were enriched under Cu stress, including the Zn2Cys6 family transcription factor GME8421_g (TH8421), which was significantly upregulated at the Cu concentration of 12.5 mg/L. ChIP-seq identified five antioxidant enzyme-encoding genes as direct targets of TH8421, forming a regulatory network that protects against Cu stress. These findings offer insights into the molecular mechanisms driving Cu toxicity tolerance in Trametes fungi.