DOPA-melanin, component and tolerance factor to heat and UV-B radiation in the conidia of two species of Cordyceps

Abstract

ABSTRACT Melanins are heterogeneous pigments present in all biological kingdoms with many biological roles, mainly related to coping with environmental stress. In some species of fungi, melanin is involved in higher virulence against plants and animals; however, little is known about the presence and type of melanin found in entomopathogenic fungi (EF), used for biological pest control. In this work, we explore the presence of melanin in conidia from Cordyceps fumosorosea CHE-CNRCB 303 and Cordyceps javanica ARSEF 3302. Melanin from both species was purified and characterised by UV, Fourier transformed infrared resonance (FT-IR) and electron paramagnetic resonance (EPR). The DOPA-melanin pathway was established as the route used by the Cordyceps genus to synthesise the pigment, which presented the ability to reduce 2,2-diphenyl-1-picrylhydrazyl (DPPH), confirming its antioxidant capacity; furthermore, the melanised conidia of both Cordyceps species were more thermotolerant and resistant to UV-B radiation than non-melanised conidia. This is the first time that melanin has been characterised and its influence on conidia quality has been verified in two Cordyceps species, which are used extensively for pest control. This knowledge could improve both the persistence of conidia in the field and the effectivity in biological control.