The AoMYB-like–AoAreB–AoAspB module links nitrogen availability to conidiation in Arthrobotrys oligospora

Nitrogen availability is an important environmental cue that influences fungal growth and developmental differentiation, yet the transcriptional mechanisms linking nitrogen status to conidiation remain poorly understood in nematode-trapping fungi. Here, we investigated the molecular mechanism underlying nitrogen-responsive conidiation in the nematode-trapping fungus Arthrobotrys oligospora . Increasing nitrogen availability promoted conidial production and was accompanied by increased expression of AoareB . Deletion of AoareB caused severe defects in hyphal development and conidiation, characterized by increased hyphal septation, reduced nuclear numbers, and decreased conidiophore and conidial production. The Δ AoareB mutant exhibited markedly reduced mycelial growth and conidiation under ammonium sulfate, glutamine, or glutamate supplementation, indicating that AoAreB contributes to nitrogen-dependent developmental responses. Mechanistically, AoAreB directly bound the promoter of the conidiation-related gene AoaspB and activated its transcription. Furtherly, AoMcm1 physically interacts with AoAreB and potentiates AoAreB-mediated transcriptional activation of AoaspB , revealing an additional layer of transcriptional co-regulation. At the upstream regulatory tier, an MYB-like transcription factor activated AoareB expression, establishing an AoMYB-like–AoAreB–AoAspB regulatory module. Functional analyses further demonstrated that AoMYB-like and AoAspB contribute to conidiation under nitrogen-supplemented conditions, particularly in the presence of ammonium sulfate, glutamine, or glutamate. This study identified an AoMYB-like–AoAreB–AoAspB regulatory module that links nitrogen availability to conidiation in A. oligospora and elucidated its molecular role in regulating nitrogen-dependent conidiation. These findings provide new insights into nitrogen-responsive developmental regulation in nematode-trapping fungi and advance the understanding of the molecular mechanisms underlying nitrogen-dependent fungal development.