Bioinformatic search of oxidoreductases involved in melanin synthesis in lichens

Abstract

Lichens are symbiotic photosynthesizing organisms whose thalli are formed by fungi and algae/cyanobacteria. Among the factors that contribute to the ability of a lichen to tolerate harsh environmental conditions is the presence of unique secondary metabolites, such as lichen acids (e.g., usnic and gyrophoric acids), catechins, polysaccharides (including lichenin), and the dark pigment melanin. Melanin is a highly polymeric pigment containing phenolic and indole groups. Information about genes encoding enzymes responsible for melanin synthesis in lichens is very limited. The main aim of the present research was to characterize genes of oxidoreductases involved in melanin synthesis in lichens. It was found that synthesis of eu- and allomelanins in lichens is supported by the activity of genes homologous to those in Ascomycota. Corresponding proteins can be oligomeric or form multidomain structures, and the interplay of these enzymes is a prerequisite for the complex process of melanin synthesis in lichens.