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A Non-canonical Melanin Biosynthesis Pathway Protects Aspergillus terreus Conidia from Environmental Stress

Elena Geib1, Markus Gressler2, Iuliia Viediernikova3

  • 1Microbial Biochemistry and Physiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Beutenbergstr. 11a, 07745 Jena, Germany; Fungal Genetics and Biology Group, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.

Cell Chemical Biology
|May 3, 2016
PubMed

Insights

Aspergillus terreus produces a novel pigment, Asp-melanin, using unique enzymes. This Asp-melanin protects fungal spores from UV light and amoeba, aiding survival in acidic conditions.

Area of Science:

  • Mycology
  • Biochemistry
  • Fungal Pathogenesis

Background:

  • Melanins are widespread pigments offering environmental protection.
  • Pathogenic fungi like Aspergillus fumigatus use dihydroxynaphthalene (DHN)-melanin in spores for virulence.
  • The melanin biosynthesis in Aspergillus terreus was previously unknown.

Purpose of the Study:

  • To elucidate the biosynthetic pathway and function of melanin in Aspergillus terreus.
  • To identify the genes and enzymes responsible for melanin production in A. terreus.

Main Methods:

  • Gene identification and characterization (NRPS-like enzyme MelA, tyrosinase TyrP).
  • Enzymatic assays to determine pigment production and activation.
  • Functional studies on Asp-melanin's protective properties (UV resistance, phagocytosis, pH stability).

Main Results:

  • Identified genes for MelA and TyrP in A. terreus, expressed during conidiation.
  • Demonstrated MelA produces aspulvinone E, polymerized by TyrP into Asp-melanin.
  • Asp-melanin provides UV resistance and hinders phagocytosis by soil amoeba.
  • Asp-melanin does not inhibit phagolysosome acidification, unlike DHN-melanin.

Conclusions:

  • A. terreus synthesizes a novel melanin (Asp-melanin) via a unique pathway.
  • Asp-melanin contributes to fungal survival in acidic environments and resistance to environmental stressors.
  • This finding expands our understanding of melanin diversity and fungal adaptation.

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