Mitochondrial mediation of environmental osmolytes discrimination during osmoadaptation in the extremely halotolerant black yeast Hortaea werneckii

We have investigated the mitochondrial responses to hyperosmotic environments of ionic (4.5 M NaCl) and non-ionic (3.0 M sorbitol) osmolytes in the most halo/osmo-tolerant black yeast, Hortaea werneckii. Adaptation to both types of osmolytes resulted in differential expression of mitochondria-related genes. Live-cell imaging has revealed a condensation of mitochondria in hyperosmotic media that depends on osmolyte type. In the hypersaline medium, this was accompanied by increased ATP synthesis and oxidative damage protection, whereas adaptation to the non-ionic osmolyte resulted in a decrease in ATP synthesis and lipid peroxidation level in mitochondria. A proteomic study of the mitochondria revealed preferential accumulation of energy metabolism enzymes in the hypersaline medium, and accumulation of protein chaperones in the non-ionic osmolyte. The HwBmh1/14-3-3 protein, localized to mitochondria in hypersaline conditions, and not at optimal salinity, suggesting its role in differential perception of ionic and non-ionic osmolytes in H. werneckii.