FgLEU1 Is Involved in Leucine Biosynthesis, Sexual Reproduction, and Full Virulence in .

Fusarium head blight (FHB) caused by is a significant disease among cereal crops. In , biosynthesis of leucine, which is a branched chain amino acid, is achieved by converting α-isopropylmalate to β-isopropylmalate catalyzed by isopropylmalate isomerase encoded by . Considering the potential for targeting this pathway by fungicides, we characterized the gene (FGSG-09589) in the genome using bioinformatics methods. For functional characterization, we constructed a deletion mutant of (Δ) through homologous recombination. Compared with the wild-type strain PH-1, Δ showed slower colony growth and fewer aerial mycelia. Leucine addition was needed to ensure proper mutant growth. Further, Δ showed decreased conidial production and germination rates, and could not produce ascospores. Moreover, Δ showed complete loss of pathogenicity and reduced ability to produce deoxynivalenol (DON) and aurofusarin. Upstream and downstream genes of were significantly upregulated in Δ. Contrary to previous reports, the deletion mutant was more resistant to osmotic stress and cell wall-damaging agents than the wild-type. Taken together, FgLEU1 plays a crucial role in leucine synthesis, aerial mycelial growth, sexual and asexual reproduction, pathogenicity, virulence, and pigmentation in , indicating its potential as a target for novel antifungal agents.