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.
Hernández-Vega et al. (Tue,) studied this question.