Nematode-trapping fungi (NTF) are a group of specialized microbial predators that consume nematodes when food sources are limited. Predation is initiated when conserved nematode ascaroside pheromones are sensed, followed by the development of complex trapping devices. To gain insights into the coevolution of this interkingdom predator–prey relationship, we investigated natural populations of nematodes and NTF that we found to be ubiquitous in soils.Arthrobotrysspecies were sympatric with various nematode species and behaved as generalist predators. The ability to sense prey among wild isolates ofArthrobotrys oligosporavaried greatly, as determined by the number of traps after exposure toCaenorhabditis elegans. While some strains were highly sensitive toC. elegansand the nematode pheromone ascarosides, others responded only weakly. Furthermore, strains that were highly sensitive to the nematode prey also developed traps faster. The polymorphic nature of trap formation correlated with competency in prey killing, as well as with the phylogeny ofA. oligosporanatural strains, calculated after assembly and annotation of the genomes of 20 isolates. A chromosome-level genome assembly and annotation were established for one of the most sensitive wild isolates, and deletion of the only G-protein β-subunit–encoding gene ofA. oligosporanearly abolished trap formation. In summary, our study establishes a highly responsiveA. oligosporawild isolate as a model strain for the study of fungus–nematode interactions and demonstrates that trap formation is a fitness character in generalist predators of the nematode-trapping fungus family.

Hog1, a mitogen-activated protein kinase (MAPK), has been identified in diverse fungal species, and it regulates various cellular processes, such as osmoadaptation, nutrient-sensing, and pathogenesis. However, the roles that Hog1 plays in nematode-trapping fungi were previously unclear. Here, we characterized orthologs of Saccharomyces cerevisiae Hog1 and membrane mucin Msb2 in the nematode-trapping fungus Arthrobotrys oligospora. We generated gene deletion mutants of HOG1 and MSB2 in A. oligospora, and characterized their roles in osmosensing, growth, and trap morphogenesis. We found that both hog1 and msb2 mutants were highly sensitive to high osmolarity. Predation analyses further revealed that hog1 and msb2 deletion caused a reduction in trap formation and predation efficiency. Furthermore, HOG1 is required for conidiation in A. oligospora, demonstrating its critical role in this developmental pathway. In summary, this study demonstrated that the conserved Hog1 and Msb2 govern physiology, growth and development in the nematode-trapping fungus A. oligospora.

Detection of surrounding organisms in the environment plays a major role in the evolution of interspecies interactions, such as predator–prey relationships. Nematode-trapping fungi (NTF) are predators that develop specialized trap structures to capture, kill, and consume nematodes when food sources are limited. Despite the identification of various factors that induce trap morphogenesis, the mechanisms underlying the differentiation process have remained largely unclear. Here, we demonstrate that the highly conserved pheromone-response MAPK pathway is essential for sensing ascarosides, a conserved molecular signature of nemaotdes, and is required for the predatory lifestyle switch in the NTF Arthrobotrys oligospora. Gene deletion of STE7 (MAPKK) and FUS3 (MAPK) abolished nematode-induced trap morphogenesis and conidiation and impaired the growth of hyphae. The conserved transcription factor Ste12 acting downstream of the pheromone-response pathway also plays a vital role in the predation of A. oligospora. Transcriptional profiling of a ste12 mutant identified a small subset of genes with diverse functions that are Ste12 dependent and could trigger trap differentiation. Our work has revealed that A. oligospora perceives and interprets the ascarosides produced by nematodes via the conserved pheromone signaling pathway in fungi, providing molecular insights into the mechanisms of communication between a fungal predator and its nematode prey.

These findings show for the first time that in the Chinese Han population, HLA-B*13:01 is associated with SASP-induced DRESS. HLA-B*13:01 might serve as a potential genetic marker for reducing the prevalence of SASP-induced DRESS.