Vol. 10, Issue 8 (2021)

Author(s):
Avinash Pilla, K Venkata Ramesh, SA Salam and Ch. S Kishore Kumar

Abstract:
Pigments are produced by most living organisms and give our world a variety of colours through the absorption and reflection of specific wavelengths of light. All pigments contain conjugated moieties (i.e. aromatics rings) that allow electronic resonances and mediate energy transfer reactions in cells. Among the biological pigments, melanins represent a unique class. Melanins are ancient biological pigments found in all kingdoms of life. In fungi, their role in microbial pathogenesis is well established. Melanin helps to tolerate extreme environments, ionizing radiation, pathogenesis, cell development etc. Melanisation is observed across all fungal Phyla, some fungal species are constitutively melanised while others melanise only under specific developmental phases (i.e. conidia, yeast filamentous growth), in response to environmental queues, and/or in the presence of phenolic melanin precursors. Melanins can be classified into eumelanins, pheomelanins, neuromelanin and allomellalins on the basis of color and constituents. A remarkable property of melanin is the capacity to interact with a wide range of electromagnetic radiation frequencies and function as a protecting and energy harvesting pigment. Melanins are products of the polymerization of phenolic compounds. Fungal melanin has been reported to promote the development of aerial hyphae and conidia that can disperse to more favourable environments. Melanin production enhances the pathogenicity of fungal infections in plants, such as Magnaporthe grisea and Colletotrichum lagenarium. Fungal melanins act as universal protectors from numerous antimicrobial factors, but the harm resulting from melanized pathogens is not controlled universally by inhibitors of melanin biosynthesis.