A Stress Hub in Scedosporium apiospermum: The High Osmolarity Glycerol (HOG) Pathway

Scedosporium species are opportunistic filamentous fungi found in human-impacted areas. Clinically relevant species, such as S. apiospermum, rank as the second most frequent colonizers of the airways of patients with cystic fibrosis (CF), which are characterized by persistent oxidative stress. This raises the question of how Scedosporium species abate conditions imposed in hostile environments. Since the High Osmolarity Glycerol (HOG) pathway plays a central role in fungal adaptation to stress, we aimed to pheno-profile the involvement of the pathway in response to stress in S. apiospermum using Western blot. We show for the first time that a wide range of stress distinctively activates the HOG pathway in S. apiospermum, including oxidants (H2O2, menadione, cumene hydroperoxide, diamide, paraquat, and honokiol), osmotic agents (sorbitol and KCl), cell-wall stress agents (caffeine, calcofluor white, and Congo Red), heavy metals (cadmium and arsenite), fungicides (fludioxonil and iprodione), antifungals (voriconazole and amphotericin B), and acid stress (pH 4). We suggest that the function of the HOG pathway as a general stress regulator is also conserved in S. apiospermum.