# Glutamine Modulates mVOC Biosynthesis in Streptomyces alboflavus Through a gluR-Dependent Signaling Pathway and Enhances Its Inhibitory Activity Against Aspergillus flavus

## TL;DR

Glutamine boosts the production of antifungal compounds in Streptomyces alboflavus, helping it fight Aspergillus flavus more effectively.

## Contribution

The study reveals a gluR-dependent signaling pathway by which glutamine modulates mVOC biosynthesis in Streptomyces alboflavus.

## Key findings

- 40 mM glutamine increased inhibition of A. flavus conidial germination by 69.0% and mycelial biomass by 64.5%.
- Transcriptome analysis identified 283 differentially expressed genes, including the upregulated two-component system regulator gluR.
- CRISPR/Cas9 disruption of gluR reduced antifungal mVOCs like dimethyl trisulfide and o-anisidine.

## Abstract

Aspergillus flavus and its aflatoxins pose serious threats to human and animal health, negatively affecting agricultural productivity and the global economy. Although chemical preservatives are widely used, their effectiveness remains limited by increased fungal resistance and environmental concerns, highlighting the need for sustainable alternatives. Microbial volatile organic compounds (mVOCs) represent a promising biocontrol strategy. Here, we investigate how glutamine regulates mVOC biosynthesis in Streptomyces alboflavus TD-1 and enhances its antifungal activity against A. flavus. Antifungal assays showed that supplementation with 40 mM glutamine significantly enhanced inhibitory activity, leading to 69.0% inhibition of conidial germination and 64.5% inhibition of mycelial biomass. Transcriptome profiling identified 283 differentially expressed genes, including the two-component system regulator gluR, which was strongly upregulated. CRISPR/Cas9-mediated disruption of gluR confirmed its regulatory role. Specifically, the mutant strain produced reduced levels of antifungal mVOCs, such as dimethyl trisulfide and o-anisidine, and exhibited diminished inhibition of A. flavus. Collectively, these findings demonstrate that exogenous glutamine enhances the mVOC-mediated suppression of A. flavus by S. alboflavus TD-1 through nutrient-sensing and transcriptional regulation of volatile biosynthesis. Although aflatoxin levels were not quantified in this study, the enhanced growth inhibition and the identified mVOC shifts provide a mechanistic basis for future studies that directly quantify aflatoxin production under storage-relevant conditions.