Systematic Analysis of the Pleurotus ostreatus Laccase Gene (PoLac) Family and Functional Characterization of PoLac2 Involved in the Degradation of Cotton-Straw Lignin

Abstract

Fungal laccases play important roles in the degradation of lignocellulose. Although some PoLacs have been reported in several studies, still no comprehensive bioinformatics study of the LAC family in Pleurotus ostreatus has been reported. In this study, we identified 12 laccase genes in the whole genome sequence of P. ostreatus and their physical characteristics, gene distribution, phylogenic relationships, gene structure, conserved motifs, and cis-elements were also analyzed. The expression patterns of 12 PoLac genes at different developmental stages and under different culture substrates were also analyzed. The results revealed that PoLac2 and PoLac12 may be involved in the degradation of lignin and the formation of the fruiting body, respectively. Subsequently, we overexpressed PoLac2 in P. ostreatus by the Agrobacterium tumefaciens-mediated transformation (ATMT) method. The transformants’ laccase activity increased in varying degrees, and the gene expression level of PoLac2 in transformants was 2–8 times higher than that of the wild-type strain. Furthermore, the lignin degradation rate by transgenic fungus over 30 days was 2.36–6.3% higher than that of wild-type. Our data show that overexpression of PoLac2 significantly enhanced the lignin degradation of cotton-straw. To our knowledge, this study is the first report to demonstrate the functions of PoLac2 in P. ostreatus.

Genes Identification, Molecular Docking and Dynamics Simulation Analysis of Laccases from Amylostereum areolatum Provides Molecular Basis of Laccase Bound to Lignin

“…We observed that laccase genes in the same group had a similar number of introns. For example, AaLac7 and AaLac8 are more closely related to the PoLac2 gene from P. ostreatus , and these genes all had complex intron-exon structures [ 51 ]. We also found that the structures of AaLac10 and AaLac12 were distinct from other laccase genes of A. areolatum , and exhibited high homology with the CcLac16 and CcLac17 genes from C. cinerea [ 54 ].…”

“…The exon theory suggested that the number and distribution of introns are related to gene evolution [ 55 ]. Thus, the more complex intron-exon structures seen in some of the laccase genes may indicate their later emergence, as over evolutionary time, introns reorder, leading to the fusion of exons to create more complex genes [ 51 , 55 ]. Analysis of the characteristics of the identified A. areolatum laccase proteins showed that, except for AaLac3, all laccases have signal peptides and no transmembrane region.…”

“…Notably, we found that AaLac10 and AaLac12 contained valine residues within the L2 region, where a conserved cysteine was typically present in classical laccases. Interestingly, the ferroxidases Mco1 and Fet3 also lacked the cysteine residue at this site [ 51 , 52 ]. Analysis of the three-dimensional crystalline structures of the laccase proteins also revealed differences in the AaLac10 and AaLac12 proteins; in all other proteins the substrate binding loops I, II, III, and IV were highly conserved and featured a cysteine residue and either an aspartic or glutamic acid in the small β-hairpin loop B4–B5, which interacted with the organic substrates [ 54 ].…”

Fungal Laccase Production from Lignocellulosic Agricultural Wastes by Solid-State Fermentation: A Review

“…The construction of genetically modified strains is an alternative way to improve the laccase yield of SSF. Overexpression of homologous or heterologous genes encoding laccase and related ligninolytic enzymes may increase the utilization rate of lignocellulosic wastes and improve laccase production [108]. In addition, heterologous expression of thermostable laccase in a thermotolerant white rot fungi provides good potential for large-scale production of laccase by SSF.…”

Dioxygen Activation by Laccases: Green Chemistry for Fine Chemical Synthesis

“…In order to meet laccase production levels for industrial applications, laccase overexpression into native hyper-producer strains should be more extensively studied as an alternative to decrease laccase cost production. Pleurotus ostreatus, Polyporus brumalis and Gloeophyllum trabeum fungal strains have been transformed for laccase homologous overexpression by different methods [78][79][80]. The constitutive overexpression of laccase in P. brumalis under the control of the glyceraldehyde-3-phosphate dehydrogenase promoter increased laccase activity 4 times higher than that of the wild-type strain [79].…”