Manganese homeostasis modulates fungal virulence and stress tolerance in Candida albicans
As transition metal availability is very limited inside the human host, fungal pathogens have evolved sophisticated mechanisms to uptake and utilize these micronutrients at the infection interface. While considerable attention was turned into iron, copper and zinc acquisition mechanisms and their importance in fungal fitness, less was done regarding either the role of Mn in infectious processes or the cellular mechanism by which fungal cells achieve their Mn-homeostasis. Here, we undertook a transcriptional profiling of the pathogenic fungus Candida albicans experiencing both Mn starvation and excess to comprehensibly capture biological processes that are modulated by Mn. We uncovered that Mn scarcity influence diverse biological processes associated with fungal fitness including morphogenetic switch, invasion of host cells and antifungal sensitivity. We also uncovered that Mn levels influence the abundance of iron and zinc emphasizing the complex crosstalk between ions metals. Deletion of SMF12, a member of Mn Nramp transporters confirmed its contribution to Mn uptake. In accordance with the RNA-seq data, smf12 was unable to form hyphae and damage host cells, and exhibited sensitivity to azole antifungals. We also found that unfolded protein response (UPR), likely activated by decreased glycosylation under Mn limitation, was essential to promote C. albicans growth. RNA-seq profiling of cells exposed to Mn excess uncovered that the UPR signaling was also essential to bypass Mn toxicity. Collectively, this study underscores the importance of Mn homeostasis in fungal virulence, and comprehensively provides a transcriptional portrait of biological functions that are modulated by Mn in a fungal pathogen. Overall design: In this study, we identified transcripts modulated under manganese (Mn) starvation by comparing the transcriptome of cells growing in Mn-depleted medium to those growing in Mn-replete medium. We also profiled cells growing under manganese excess by comparing the transcriptome of cells treated with 7.5 mM MnCl2 to that of the control condition.