2.1.3. Zinc Tolerance and Resistance

High-zinc environments can be detrimental to fungi; therefore they must possess resistance mechanisms to overcome toxicity. In yeast, resistance relies on the upregulation of Zrc1 and Cot1, which sequester Zn2+ to the vacuole (up to 100 mM) in *S. cerevisiae*, or the endoplasmic reticulum in *C. albicans* (Zrc1) [105–108,169]. Khouja et al. also described a resistance mechanism via OmFET in *S. cerevisiae*, though it is not yet fully understood [170]. They suggest that OmFET plays a role in Zn2+ uptake, and in that role increases tolerance through interactions with Mg, where Mg competes with Zn2+ for uptake, increasing intracellular Mg and restricting Zn [170]. In filamentous fungi, zinc resistance is not only attributed to vacuolar sequestration, but also to storage in the cytoplasm, storage in cell walls of spores and hyphae, and cellular efflux; and in ectomycorrhizal fungi, the presence of metallothionein-like peptides confers Zn2+ resistance [110,171–173]. To further investigate how fungi cope with toxic levels of other micronutrient metals, this review also assessed cellular interactions with copper.
