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 <i>PoLac</i>s have been reported in several studies, still no comprehensive bioinformatics study of the <i>LAC</i> family in <i>Pleurotus ostreatus</i> has been reported. In this study, we identified 12 laccase genes in the whole genome sequence of <i>P. ostreatus</i> and their physical characteristics, gene distribution, phylogenic relationships, gene structure, conserved motifs, and cis-elements were also analyzed. The expression patterns of 12 <i>PoLac</i> genes at different developmental stages and under different culture substrates were also analyzed. The results revealed that <i>PoLac2</i> and <i>PoLac12</i> may be involved in the degradation of lignin and the formation of the fruiting body, respectively. Subsequently, we overexpressed <i>PoLac2</i> in <i>P. ostreatus</i> by the <i>Agrobacterium tumefaciens</i>-mediated transformation (ATMT) method. The transformants' laccase activity increased in varying degrees, and the gene expression level of <i>PoLac2</i> 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 <i>PoLac2</i> significantly enhanced the lignin degradation of cotton-straw. To our knowledge, this study is the first report to demonstrate the functions of <i>PoLac2</i> in <i>P. ostreatus</i>.