K404 Acetylation of Glutamate Dehydrogenase CrGdh2 Is Necessary for Mycoparasitism of Clonostachys chloroleuca against Sclerotinia sclerotiorum

Clonostachys chloroleuca is a potential biocontrol fungus capable of parasitizing various plant fungal pathogens. In the highly efficient strain 67-1, we identified a glutamate dehydrogenase gene, CrGdh2, during mycoparasitization of Sclerotinia sclerotiorum. CrGdh2 is essential for the biocontrol activity of C. chloroleuca, as its deletion compromised control efficacy against Sclerotinia rot and tomato root rot by 27.9% and 39.8%, respectively, compared to the wild-type strain. Acetylated CrGdh2 was investigated using acetylation and deacetylation mimetic mutants. The results showed that when strains were inoculated on S. sclerotiorum sclerotia, no obvious infection structures were detected in ΔCrGdh2 and ΔCrGdh2-C^K404R. In pot experiments, both mutants also showed over 30% reduction in biocontrol efficacy, in contrast to the wild-type and ΔCrGdh2-C^K404Q strains, indicating the essential role of K404 acetylation. The findings reveal the roles of glutamate dehydrogenase and its acetylation in mycoparasitism, providing novel insight into the biocontrol mechanisms of C. chloroleuca.