Hog1B is Required for Spore Germination, Stress Response and Fungal Morphogenesis in Mucor lusitanicus

Mucor lusitanicus is a dimorphic fungus that causes the rare but fatal fungal infection mucormycosis in human with compromised immune systems. Hog1 is a mitogen-activated protein kinase (MAPK) that initiates various responsive changes in transcription and translation, mitosis, and metabolism under stress conditions. In many fungi, the Hog1 protein play a role in response to stress such as osmotic, oxidative, heavy metal stress, as well as morphogenesis and virulence. To investigate the functions of Hog1pB protein in M. lusitanicus, a hog1B-silencing strain corresponding to Hog1pB protein (ID 157309) were generated using RNAi technique. The hog1B-suppressed fungal strain was evaluated in morphological and stress response characteristics. The silencing strain showed a considerably lower spore germination rate and an aberrant mycelia phenotype with unusually short, septate, inflated hyphae and the presence of yeast-like structures. Furthermore, in the presence of H₂O₂ as an oxidant, the hog1B knock-down strain of M. lusitanicus exhibits decreased spore germination and viability. Under osmotic stress conditions, this silencing strain also displayed aberrant mycelia morphology and spore germination rate depletion. However, Hog1pB appears to have no influence on M. lusitanicus spore aerobic germination under thermal stress. The data imply that the Hog1pB protein plays an important role in M. lusitanicus septation, morphology, and pathogenicity. The findings suggested that the Hog1pB protein as a possible target for future mucormycosis treatment.

The online version contains supplementary material available at 10.1007/s12088-024-01426-z.