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

Xiaoyu Jiao,Guoqing Li,Yi Lin,Fan Nie,Muhammad Abdullah,Yongping Cai,Xi Cheng,Yan Wang

doi:10.3390/molecules23040880

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.

Highlights

Laccase is a kind of multi-copper polyphenol oxidase which belongs to the group of copper blue oxidase protein family (MCOs) and can catalyze the oxidation of various phenolic and non-phenolic compounds [1]
The results of this study provide a new insight into how white-rot basidiomycetes accomplish lignin degradation and provides useful guidance for extending the application of P. ostreatus laccase
12 members of the laccase multigene family were identified in the whole genome of P. ostreatus (Table 1), which is same as the gene sequence that was previously annotated as laccase in the P. ostreatus genome [14]

Summary

Introduction

Laccase is a kind of multi-copper polyphenol oxidase which belongs to the group of copper blue oxidase protein family (MCOs) and can catalyze the oxidation of various phenolic and non-phenolic compounds [1]. Other members of this family include ascorbate oxidases (EC 1.10.3.3), ceruloplasmin (EC 1.16.3.1), and ferroxidases [2]. Fungal laccase plays an important role in the biological process of fruiting body development, pigment formation, and stress resistance. Laccase, as an enzyme of broad substrate specificity in the lignin-degrading enzymes, plays an important role in the decolorization of textile dyes [5], pulp bleaching [6], and lignin degradation [7]. Fungal laccase generally contains four copper molecules, the mononuclear center

Methods

Results

Conclusion