1887

Abstract

Melanin is a black pigment widely distributed across the kingdoms, from bacterial to human. The filamentous fungus is a typical ‘black fungus’, which produces melanin in its hyphal and especially its asexual spore cell walls. Its biosynthesis follows the dihydroxynaphthalene (DHN) pathway with 1,8-DHN as an intermediate. Two genes, encoding a polyketide synthase () and a 1,3,8-trihydroxynaphthalene (THN) reductase (), along with a putative transcription factor, CmrA, comprise a small gene cluster. Here we show that CmrA controls the expression of and , but that it also controls the expression of a scytalone dehydratase encoding gene () located elsewhere in the genome. The regulatory function of CmrA was shown in a reporter assay system. CmrA was expressed in the filamentous fungus where it was able to induce the expression of a reporter construct under the control of the putative promoter. This suggests direct binding of CmrA to the promoter of in the heterologous system. Likewise, silencing of in led to white colonies due to the lack of melanin. In addition, hyphal diameter and spore morphology were changed in the mutant and the number of spores reduced. Silencing of and inhibition of melanin biosynthesis by tricyclazole largely phenocopied the effects of silencing, suggesting a novel regulatory function of melanin in morphogenetic pathways.

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2014-09-01
2019-11-21
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