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Updated: May 14, 2026

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An ancient gene duplication is implicated in virulence in the human pathogen, Histoplasma

Victoria E Sepúlveda, Jingbaoyi Li, David A Turissini

    Biorxiv : the Preprint Server for Biology
    |May 13, 2026
    PubMed

    Insights

    Researchers discovered new alpha-amylase genes (AMY2 and AMY3) in Histoplasma, a fungus causing infections. These genes play varied roles in alpha-glucan production and virulence, with AMY2 being partially involved and AMY3 dispensable.

    Area of Science:

    • Mycology
    • Fungal Pathogenesis
    • Molecular Biology

    Background:

    • Histoplasma spp. is a dimorphic fungal pathogen causing worldwide infections, particularly in immunocompromised individuals.
    • The alpha-amylase Amy1p, encoded by the AMY1 gene, is crucial for alpha-glucan production and virulence in Histoplasma capsulatum.
    • Understanding the roles of other alpha-amylase genes in Histoplasma is essential for elucidating its pathogenesis.

    Purpose of the Study:

    • To identify and characterize novel alpha-amylase genes (AMY2 and AMY3) in the Histoplasma genome.
    • To investigate the involvement of these new genes in alpha-glucan biosynthesis and fungal virulence.
    • To explore the evolutionary history and distribution of AMY genes across different fungal species.

    Main Methods:

    • Identification of AMY2 and AMY3 genes in the Histoplasma genome.
    • Construction of gene knockout mutants using CRISPR/Cas9 technology.
    • Phylogenetic analysis and comparative genomics of AMY genes across 19 fungal species.
    • Assessment of alpha-glucan production and virulence in generated mutants.

    Main Results:

    • Two new putative alpha-amylase genes, AMY2 and AMY3, were identified in Histoplasma.
    • AMY2 is partially involved in alpha-glucan biosynthesis and virulence, and is an ortholog of Aspergillus niger AgtA and Aspergillus nidulans AmyD.
    • AMY3 is dispensable for alpha-glucan biosynthesis and virulence, and is an ortholog of Aspergillus flavus Amy1.
    • Phylogenetic analyses revealed ancient duplications of AMY genes in Histoplasma, with varying numbers and types of alpha-amylases across fungal species.

    Conclusions:

    • The Histoplasma genome contains multiple ancient alpha-amylase genes with distinct roles in virulence and alpha-glucan production.
    • AMY2 contributes partially to Histoplasma pathogenesis, while AMY3 is not essential.
    • Comparative genomic and phylogenetic analyses provide insights into the evolution of alpha-amylase genes in fungi.

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