# AoMbp1 Governs Conidiation and Trap Morphogenesis in Arthrobotrys oligospora Via Direct Transcriptional Activation of the MAPK Sensor AoSho1

## TL;DR

This study identifies AoMbp1 as a key regulator in a fungus that traps nematodes, controlling its growth, stress tolerance, and trap formation.

## Contribution

The discovery of AoMbp1's direct activation of AoSho1 establishes a new regulatory mechanism in nematode-trapping fungi.

## Key findings

- AoMbp1 deletion impairs growth, conidiation, trap formation, and stress tolerance in A. oligospora.
- AoMbp1 directly activates AoSho1, a key MAPK sensor, linking transcriptional regulation to trap morphogenesis.
- Transcriptome analysis shows widespread gene downregulation in the MAPK pathway upon AoMbp1 deletion.

## Abstract

The nematode-trapping fungus (NTF) Arthrobotrys oligospora (A. oligospora) is a promising biocontrol agent, but the transcriptional regulators governing its predation remain poorly understood. Here, we demonstrated that the APSES transcription factor AoMbp1 is a master regulator of its development and stress adaptation. Deletion of AoMbp1 severely impaired mycelial growth, conidiation, trap formation, and tolerance to oxidative and osmotic stresses. Transcriptome analysis revealed that these defects were associated with the widespread downregulation of genes, including those within the MAPK signaling pathway. Crucially, we showed that AoMbp1 directly binds to the promoter of AoSho1, a key upstream sensor of the MAPK cascade, and activates its expression. This finding establishes a direct AoMbp1-AoSho1 regulatory axis controlling trap morphogenesis and environmental adaptation. Our study provides novel mechanistic insights into the regulation of nematode trapping and identifies a potential target for enhancing the efficacy of A. oligospora as a biocontrol agent.