Orchestration of the expression of the laccase multigene family in white-rot basidiomycete Trametes hirsuta 072: Evidences of transcription level subfunctionalization

Laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) is an enzyme that has been studied for over 100 y and is present in virtually all fungi. As increasing numbers of fungal genomes have been sequenced, it has become apparent that the laccase genes in white-rot fungi commonly form multigene families consisting of many nonallelic genes. Although a number of reports focussing on laccase gene expression in different fungal species were published over the decades, the fundamental questions of why fungi need such a redundant array of genes and how they manage this array to perform biological function(s) remain far from answered. In this article, we present a comprehensive study of the transcription of the whole Trametes hirsuta laccase multigene family under different conditions, including exposure to different nutritional factors such as nitrogen sources (organic and inorganic) and concentrations of nitrogen and carbon in the culture medium; in different growth phases (lag phase and stationary phase); and in the presence of different inducer agents (water-soluble lignin, bromocresol green dye, p-coumaric acid, ferulic acid, guaiacol, vanillin, veratryl alcohol, vanillic acid and syringic acid). Our findings are discussed in the context of the evolution of the laccase multigene family, and the presence of transcription-level sub-functionalization is highlighted. (C) 2018 British Mycological Society. Published by Elsevier Ltd. All rights reserved.