Transcriptional profiles of laccase genes in the brown rot fungus Postia placenta MAD-R-698

Abstract

One of the laccase isoforms in the brown rot fungus Postia placenta is thought to contribute to the production of hydroxyl radicals, which play an important role in lignocellulose degradation. However, the presence of at least two laccase isoforms in this fungus makes it difficult to understand the details of this mechanism. In this study, we systematically investigated the transcriptional patterns of two laccase genes, Pplcc1 and Pplcc2, by quantitative PCR (qPCR) to better understand the mechanism. The qPCR results showed that neither of the two genes was expressed constitutively throughout growth in liquid culture or during the degradation of a woody substrate. Transcription of Pplcc1 was upregulated under nitrogen depletion and in response to a high concentration of copper in liquid culture, and during the initial colonization of intact aspen wafer. However, it was subject to catabolite repression by a high concentration of glucose. Transcription of Pplcc2 was upregulated by stresses caused by ferulic acid, 2, 6-dimethylbenzoic acid, and ethanol, and under osmotic stress in liquid culture. However, the transcription of Pplcc2 was downregulated upon contact with the woody substrate in solid culture. These results indicate that Pplcc1 and Pplcc2 are differentially regulated in liquid and solid cultures. Pplcc1 seems to play the major role in producing hydroxyl radicals and Pplcc2 in the stress response during the degradation of a woody substrate.

Transcriptome Sequencing and Comparative Analysis of Piptoporus betulinus in Response to Birch Sawdust Induction

“…However, in the past published papers, P. betulinus was thought to modify the structure of lignin instead of degrading lignin, which involve complex phenolic polymers composed of cinnamyl alcohol subunits, phenylpropanol and its derivatives [33]. Therefore, our paper speculated that those metabolic pathways in P. betulinus transcriptome were likely to participate in lignin modification.…”

Laccases in the Context of Potentially Cooperating Enzymes

“…The latter are reduced back to hydroquinones by CAZy AA3 or AA6 oxidoreductases. The figure was compiled based on information from the following references: An et al (2015), Aranda et al (2010), Gomez-Toribio et al (2009a, b), Guillen et al (1997Guillen et al ( , 2000, Krueger et al (2016Krueger et al ( , 2015, Marco-Urrea et al…”

“…A few reports describe the expression of laccase and the occurrence of corresponding genes in certain brown rot fungi (An et al 2015;Bissaro et al 2018;Wei et al 2009). Laccases may alternatively oxidize diphenols under conditions where abiotic oxidation of the latter is impeded by high concentrations of the strong Fe 3+ chelator oxalate, which is produced by many brown rot basidiomycetes and secreted concomitantly with fungal diphenols (An et al 2015;Wei et al 2010). Laccases rapidly oxidize diphenols/hydroquinones to the corresponding semiquinones and thus can replace or boost abiotic diphenol oxidation, hereby becoming a part of the quinone redox cycling machinery described before.…”

Expression Profile of Laccase Gene Family in White-Rot Basidiomycete Lentinula edodes under Different Environmental Stresses

“…In plants, laccases participate in the radical-based mechanisms of lignin polymer formation [14,15], while in fungi, laccases are thought to play a variety of physiological roles, including stress defense, melanin synthesis [10], fruiting-body formation, and lignin degradation [7]. The transcription of laccase genes in various organisms (mostly fungi) is affected by many factors, such as the type and nature of nutrients, temperature, pH, and chemical inducers, and also varies with the phases of fruiting-body development [9,11,12,16]. In recent years, a number of reports were published regarding the genetic functional analysis of laccases in mushrooms, such as Pleurotus ostreatus, Hypsizygus marmoreus, and Lentinula edodes [17][18][19][20].…”