Pleurotus ostreatus is frequently used in molecular genetics and genomic studies on white-rot fungi because various molecular genetic tools and relatively well-annotated genome databases are available. To explore the molecular mechanisms underlying wood lignin degradation by P. ostreatus, we performed mutational analysis of a newly isolated mutant UVRM28 that exhibits decreased lignin-degrading ability on the beech wood sawdust medium. We identified that a mutation in the hir1 gene encoding a putative histone chaperone, which probably plays an important role in DNA replication-independent nucleosome assembly, is responsible for the mutant phenotype. The expression pattern of ligninolytic genes was altered in hir1 disruptants. The most highly expressed gene vp2 was significantly inactivated, whereas the expression of vp1 was remarkably upregulated (300–400 fold) at the transcription level. Conversely, many cellulolytic and xylanolytic genes were upregulated in hir1 disruptants. Chromatin immunoprecipitation analysis suggested that the histone modification status was altered in the 5ʹ-upstream regions of some of the up- and down-regulated lignocellulolytic genes in hir1 disruptants compared with that in the 20b strain. Hence, our data provide new insights into the regulatory mechanisms of lignocellulolytic genes in P. ostreatus.

Pleurotus ostreatus经常用于白腐真菌的分子遗传学和基因组研究，因为可以使用各种分子遗传工具和相对完善的基因组数据库。为了探索P. ostreatus降解木材木质素的分子机制，我们对新分离的突变体 UVRM28 进行了突变分析，该突变体在山毛榉木锯末培养基上表现出降低的木质素降解能力。我们发现编码假定的组蛋白伴侣的hir1基因中的突变可能在不依赖 DNA 复制的核小体组装中起重要作用，是导致突变表型的原因。木质素分解基因的表达模式在改变hir1破坏者。最高表达的基因vp2显着失活，而vp1 的表达在转录水平上显着上调（300-400 倍）。相反，许多纤维素分解和木聚糖分解基因在hir1破坏株中上调。染色质免疫沉淀分析表明，与 20b 菌株相比，hir1破坏株中一些上调和下调的木质纤维素分解基因的 5ʹ-上游区域的组蛋白修饰状态发生了改变。因此，我们的数据为P. ostreatus中木质纤维素分解基因的调控机制提供了新的见解。