Humicolopsis cephalosporioides synthesizes DHN-melanin in its chlamydospores

Abstract

Humicolopsis cephalosporioides is a soil fungus that is associated with Nothofagus forests in South America. The aim of this study was to analyze the effect of environmental factors such as temperature, light, and nutrition on chlamydospore differentiation as well as pigment biosynthesis. Temperature did not affect chlamydospore production; it rather altered pigmentation development that also was affected by light. The composition of culture media as well as light modulated chlamydospore differentiation. Microscope observations, spectroscopic analysis as well as culture assays, using melanin inhibitors, suggest that the main pigment of chlamydospores of H. cephalosporioides is 1,8 dihydroxynaphthalene (DHN)-melanin–type compound. Furthermore, we found that the genome of H. cephalosporioides contains a sequence highly homologous to the pks sequences of other fungi that have been associated with the biosynthesis of 1,8 DHN-melanin. All this together suggests that melanization is among the most important features linked to survival of this fungus in the soils of Nothofagus forests in sub-Antarctica region and that the ITS, 18S, and 28S rDNA sequences did not provide enough information to delineate the phylogenetic relationships of the fungus within the class Leotiomycetes.