Proteomic insight into the ectomycorrhizal fungus Laccaria bicolor illuminates the central role of glutathione-mediated resistance to cadmium toxicity.

Ectomycorrhizal (ECM) fungi play a vital role in the bioremediation of heavy metal contaminated soil and protecting the host plants from metal stress. In this study, we employed a comparative proteomic approach to investigate the molecular response of ECM fungus Laccaria bicolor to cadmium (Cd) stress. Out of total 997 proteins identified, 154 proteins with a fold change ≥ 1.5 and p < 0.05 were classified as differentially abundant proteins (DAPs) and selected for analysis. KEGG-based functional annotation revealed that Cd exposure disrupted key metabolic pathways including carbohydrate, nucleotide and energy metabolism, thereby inducing cellular energy stress. Proteins involved in genetic information processing, such as DNA replication, repair, transcription, translation, and protein folding, were significantly downregulated, indicating genomic instability and impaired protein quality control. Furthermore, Cd stress affected cellular homeostasis by altering membrane transport and vesicular trafficking systems. In response, L. bicolor activated multiple defense mechanisms to counteract the Cd toxicity, notably upregulating the proteins involved in oxidative stress mitigation, particularly those associated with glutathione metabolism, as well as MAPK and calcium signaling pathways. The consistent upregulation of glutathione and many other related enzymes highlight their central role in Cd detoxification. Overall, this study provides comprehensive insights into the molecular strategies deployed by L. bicolor for Cd tolerance, identifying potential biomarkers and target genes for future biotechnological applications in phytoremediation and stress resilience. Also, this study highlights the active role of glutathione biosynthesis and metabolism proteins in Cd stress mitigation.