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

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