Search Results (2)

Nematode-trapping fungi are saprophytic organisms that can transform their mycelium into a parasitic lifestyle, forming traps to capture and feed on nematodes. Although this transition is triggered by environmental conditions, the genetic regulation of this metabolic shift remains unclear. This study assessed the effects of nutritional stress on mycochemical synthesis, trap morphogenesis, and Aomae1 gene expression in Arthrobotrys oligospora and Arthrobotrys musiformis. Fungal biomass was subjected to the following three-stage successive culture model: (i) nutrient-rich (Czapek–Dox broth), (ii) nutritional stress (water), and (iii) media enriched with live prey (Haemonchus contortus Hc-L₃). Samples were taken for molecular analysis, and liquid culture filtrates (LCFs) were recovered for chromatographic identification of mycochemical groups. To assess trap formation (traps/cm²), mycelia from each culture model was transferred to water agar plates and defied with Hc-L₃. Results showed a significant bioenergetic trade-off. Both starvation and larval presence induced a downregulation of mycochemical synthesis, which resulted in the total loss of nematocidal activity in LCfs, while triggering a morphogenetic response. Arthrobotrys musiformis showed the most aggressive phenotype with 3.8-fold increase in trap formation and a massive 429.05-fold overexpression of Aomae1 under predatory challenge. While A. oligospora showed a similar but less pronounced trend (2.4-fold increase in trap formation and 44.48-fold Aomae1 overexpression), our findings suggest that Aomae1 expression plays a critical role in the metabolic switch that regulates and redirects energy resources, prioritizing mechanical trapping mechanisms over secondary metabolism during nutrient scarcity. These findings highlight Aomae1 as a possible key activator for virulence, which offers strategic targets for the optimization of biocontrol agents against gastrointestinal nematodes in livestock. Full article

Malate dehydrogenase (MDH) is a key enzyme in the tricarboxylic acid (TCA) cycle and is essential for energy balance, growth, and tolerance to cold and salt stresses in plants. However, the role of MDH in filamentous fungi is still largely unknown. In this study, we characterized an ortholog of MDH (AoMae1) in a representative nematode-trapping (NT) fungus Arthrobotrys oligospora via gene disruption, phenotypic analysis, and nontargeted metabolomics. We found that the loss of Aomae1 led to a weakening of MDH activity and ATP content, a remarkable decrease in conidia yield, and a considerable increase in the number of traps and mycelial loops. In addition, the absence of Aomae1 also caused an obvious reduction in the number of septa and nuclei. In particular, AoMae1 regulates hyphal fusion under low nutrient conditions but not in nutrient-rich conditions, and the volumes and sizes of the lipid droplets dynamically changed during trap formation and nematode predation. AoMae1 is also involved in the regulation of secondary metabolites such as arthrobotrisins. These results suggest that Aomae1 has an important role in hyphal fusion, sporulation, energy production, trap formation, and pathogenicity in A. oligospora. Our results enhance the understanding of the crucial role that enzymes involved in the TCA cycle play in the growth, development, and pathogenicity of NT fungi. Full article