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Deciphering the Role of PIG1 and DHN-Melanin in Scedosporium apiospermum Conidia
Hélène Guegan1, Wilfried Poirier2, Kevin Ravenel2
1CHU Rennes, INSERM, EHESP, IRSET (Institut de Recherche en Santé Environnement et Travail)-UMR_S 1085, 35000 Rennes, France.
Abstract:
Scedosporium apiospermum is a saprophytic filamentous fungus involved in human infections, of which the virulence factors that contribute to pathogenesis are still poorly characterized. In particular, little is known about the specific role of dihydroxynaphtalene (DHN)-melanin, located on the external layer of the conidia cell wall. We previously identified a transcription factor, PIG1, which may be involved in DHN-melanin biosynthesis. To elucidate the role of PIG1 and DHN-melanin in S. apiospermum, a CRISPR-Cas9-mediated PIG1 deletion was carried out from two parental strains to evaluate its impact on melanin biosynthesis, conidia cell-wall assembly, and resistance to stress, including the ability to survive macrophage engulfment. ΔPIG1 mutants did not produce melanin and showed a disorganized and thinner cell wall, resulting in a lower survival rate when exposed to oxidizing conditions, or high temperature. The absence of melanin increased the exposure of antigenic patterns on the conidia surface. PIG1 regulates the melanization of S. apiospermum conidia, and is involved in the survival to environmental injuries and to the host immune response, that might participate in virulence. Moreover, a transcriptomic analysis was performed to explain the observed aberrant septate conidia morphology and found differentially expressed genes, underlining the pleiotropic function of PIG1.
Insights
The transcription factor PIG1 regulates dihydroxynaphthalene (DHN)-melanin in Scedosporium apiospermum. Deleting PIG1 impacts fungal cell walls, stress resistance, and survival against host immune responses, suggesting a role in virulence.
Area of Science:
- Medical Mycology
- Fungal Pathogenesis
- Molecular Biology
Background:
- Scedosporium apiospermum causes human infections, but its virulence factors are poorly understood.
- The role of dihydroxynaphthalene (DHN)-melanin in the conidia cell wall of S. apiospermum pathogenesis is largely unknown.
- PIG1, a transcription factor, was previously identified as potentially involved in DHN-melanin biosynthesis.
Purpose of the Study:
- To investigate the function of PIG1 in S. apiospermum.
- To determine the impact of DHN-melanin on fungal cell wall integrity and stress resistance.
- To assess the role of PIG1 and DHN-melanin in S. apiospermum's interaction with the host immune system.
Main Methods:
- CRISPR-Cas9 gene editing was used to create PIG1 deletion mutants (ΔPIG1) in S. apiospermum.
- Melanin production, conidia cell wall structure, and resistance to oxidative stress and heat were evaluated.
- Macrophage engulfment assays and transcriptomic analysis were performed.
Main Results:
- ΔPIG1 mutants lacked melanin and exhibited disorganized, thinner cell walls.
- Melanin-deficient mutants showed reduced survival under oxidative and thermal stress.
- Absence of melanin exposed more antigenic patterns, and PIG1 deletion impaired survival against host immune responses.
Conclusions:
- PIG1 is a key regulator of melanization in S. apiospermum conidia.
- DHN-melanin and PIG1 contribute to fungal survival against environmental stresses and host immunity.
- PIG1 has pleiotropic functions, influencing cell wall assembly and virulence of S. apiospermum.
