Comparative transcriptomics provides insight into molecular mechanisms of zinc tolerance in the ectomycorrhizal fungus Suillus luteus

Zinc is a major soil contaminant and high zinc levels can disrupt growth, survival, and reproduction of fungi. Some fungal species have evolved zinc tolerance through cell processes mitigating zinc toxicity, though the genes and detailed mechanisms underlying fungal zinc tolerance remain unexplored. To fill this gap in knowledge, we investigated the gene expression of zinc tolerance in the mycorrhizal fungus Suillus luteus. We found that zinc tolerance in this species is both a constitutive and environmentally dependent trait. Highly differentially expressed genes were predicted to be involved in transmembrane transport, metal chelation, oxidoreductase activity, and signal transduction. Some of these genes were previously reported as candidates for S. luteus zinc tolerance, while others are reported here for the first time. Overall, we found S. luteus zinc tolerance is associated with differences in expression of genes involved in metal exclusion and immobilization, as well as recognition and mitigation of metal-induced oxidative stress. Our results contribute to understanding the mechanisms of fungal metal tolerance and pave the way for further research on the role of metal tolerance in mycorrhizal associations.