Gluconolactonase SMP30 deletion worsens fungal degeneration through ROS accumulation and mitochondrial dysfunction in...

Gluconolactonase/Senescence marker protein 30 (SMP30) is a multifunctional enzyme involved in L-ascorbic acid biosynthesis, ROS scavenging, and aging in mammals, but its role in fungi remains partially understood.

Here, we demonstrate that an SMP30 (MrSMP30-1) from the entomopathogenic fungus Metarhizium robertsii is essential for ROS elimination and mitochondrial function. Phylogenetic analysis shows that MrSMP30-1 is more closely related to SMP30 proteins from phytopathogenic fungi than to those from other entomopathogens. Recombinant MrSMP30-1 displays maximum lactonase activity at pH 6.5 and 25 °C. Deletion of MrSMP30-1 results in intracellular ROS buildup, a significant decrease in lipid droplets, and collapse of mitochondrial membrane potential, leading to accelerated, spontaneous fungal degeneration. Virulence tests indicate that the loss of MrSMP30-1 reduces pathogenicity. Immunoprecipitation combined with mass spectrometry identified seven proteins, including polyketide synthase 3, that potentially interact physically with MrSMP30-1.

Our results indicate that the gluconolactonase MrSMP30-1 is essential for ROS detoxification and preserving mitochondrial integrity in M. robertsii. This not only enhances our understanding of SMP30's proposed role in fungi but also suggests that it could serve as a biomarker for monitoring fungal culture degeneration. © 2025 Society of Chemical Industry.