Identification and Characterization of an Antifungal Gene Mt1 from Bacillus subtilis by Affecting Amino Acid Metabolism in Fusarium graminearum

Fusarium head blight is a devastating disease that causes significant economic losses worldwide. Fusarium graminearum is a crucial pathogen that requires close attention when controlling wheat diseases. Here, we aimed to identify genes and proteins that could confer resistance to F. graminearum. By extensively screening recombinants, we identified an antifungal gene, Mt1 (240 bp), from Bacillus subtilis 330-2. We recombinantly expressed Mt1 in F. graminearum and observed a substantial reduction in the production of aerial mycelium, mycelial growth rate, biomass, and pathogenicity. However, recombinant mycelium and spore morphology remained unchanged. Transcriptome analysis of the recombinants revealed significant down-regulation of genes related to amino acid metabolism and degradation pathways. This finding indicated that Mt1 inhibited amino acid metabolism, leading to limited mycelial growth and, thus, reduced pathogenicity. Based on the results of recombinant phenotypes and transcriptome analysis, we hypothesize that the effect of Mt1 on F. graminearum could be related to the metabolism of branched-chain amino acids (BCAAs), the most affected metabolic pathway with significant down-regulation of several genes. Our findings provide new insights into antifungal gene research and offer promising targets for developing novel strategies to control Fusarium head blight in wheat.