Abstract
Melanins are the common fungal pigment, which contribute to stress resistance and pathogenesis. However, few studies have explored the regulation mechanism of its synthesis in filamentous fungi. In this study, we identified two transcription factors, Pmr1 and Pmr2, in the filamentous fungus Pestalotiopsis microspora. Computational and phylogenetic analyses revealed that Pmr1 and Pmr2 were located in the gene cluster for melanin biosynthesis. The targeted deletion mutant strain Δpmr1 displayed defects in biosynthesis of conidia pigment and morphological integrity. The deletion of pmr2 resulted in reduced conidia pigment, but the mycelial morphology had little change. Moreover, Δpmr2 produced decreased conidia. RT-qPCR data revealed that expression levels of genes in the melanin biosynthesis gene cluster were downregulated from the loss of Pmr1 and Pmr2. Interestingly, the yield of secondary metabolites in the mutant strains Δpmr1 and Δpmr2 increased, comparing with the wild type, and additionally, Pmr1 played a larger regulatory role in secondary metabolism. Taken together, our results revealed the crucial roles of the transcription factors Pmr1 and Pmr2 in melanin synthesis, asexual development and secondary metabolism in the filamentous fungus P. microspora.
Highlights
The production of pigments can be consistently observed during the growth and development of filamentous fungi, among which the most common forms are melanins
Our results revealed the crucial roles of the transcription factors Pmr1 and Pmr2 in melanin synthesis, asexual development and secondary metabolism in the filamentous fungus P. microspora
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Summary
The production of pigments can be consistently observed during the growth and development of filamentous fungi, among which the most common forms are melanins. Previous studies have shown that melanins contribute to high-radiation protection, microbe survival and fungal virulence [2,3]. A large population of melanotic fungal species were isolated from the contaminated soil of Chernobyl [4], demonstrating the crucial roles of melanin in protecting against radiation exposure. Melanins are critical for the virulence of pathogenic fungi and promote fungal invasion and colonization in humans, animals, and plants. In Penicillium marneffei, melanins block host defense mechanisms to increase fungal virulence [5]. Recent observations suggest that the production of melanin is related to the integrity of fungal cell wall [6,7]
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