Functional analysis of the mitochondrial gene mitofilin in the filamentous entomopathogenic fungus Beauveria bassiana

Mitofilin acts as an essential organizer that maintains the complex architecture of the mitochondrial inner membrane (IM). In the present study, a yeast ortholog of mitofilin was characterized in the filamentous entomopathogenic fungus Beauveria bassiana; hence, it was named BbMtf. Mitochondrial localization was observed for B. bassiana mitofilin, and loss of this protein altered both the overall morphology and crista junction of the mitochondrial IM. Disruption of BbMtf resulted in reduced ATP synthesis and germination on the oligotrophic surface compared to the control. The ΔBbMtf mutant did not display significant variation in mycelial growth and stress tolerance. However, the BbMtf gene was required for conidiation and blastospore formation, and its absence led to a significant reduction in conidiation (40%) and blastospore yield (70%) in the mutant strain compared to the control. In addition, the development of the ΔBbMtf mutant in the host hemocoel was also significantly impaired, with a reduction of approximately 80% in spore concentration. Finally, disruption of BbMtf significantly attenuated fungal pathogenicity against insect hosts. Mitofilin, therefore, maintains the function of the mitochondrial IM, which contributes to the development and virulence of B. bassiana as a biocontrol fungus.