The ascomycete Trichoderma reesei is a highly prolific cellulase producer. While XYR1 (Xylanase regulator 1) has been firmly established to be the master activator of cellulase gene expression in T. reesei, its precise transcriptional activation mechanism remains poorly understood. In the present study, TrGAL11, a component of the Mediator tail module, was identified as a putative interacting partner of XYR1. Deletion of Trgal11 markedly impaired the induced expression of most (hemi)cellulase genes, but not that of the major β-glucosidase encoding genes. This differential involvement of TrGAL11 in the full induction of cellulase genes was reflected by the RNA polymerase II (Pol II) recruitment on their core promoters, indicating that TrGAL11 was required for the efficient transcriptional initiation of the majority of cellulase genes. In addition, we found that TrGAL11 recruitment to cellulase gene promoters largely occurred in an XYR1-dependent manner. Although xyr1 expression was significantly tuned down without TrGAL11, the binding of XYR1 to cellulase gene promoters did not entail TrGAL11. These results indicate that TrGAL11 represents a direct in vivo target of XYR1 and may play a critical role in contributing to Mediator and the following RNA Pol II recruitment to ensure the induced cellulase gene expression.

子囊里氏木霉是一种高产的纤维素酶生产商。虽然XYR1（木聚糖酶调节剂1）已被牢固地确定为T中纤维素酶基因表达的主要激活因子。里氏，其精确的转录激活机制仍知之甚少。在本研究中，TrGAL11是介体尾巴模块的一个组件，被确定为XYR1的假定相互作用伙伴。删除Trgal11显着削弱了大多数（半）纤维素酶基因的诱导表达，但没有削弱主要的β-葡萄糖苷酶编码基因的诱导表达。在其核心启动子上募集的RNA聚合酶II（Pol II）可反映TrGAL11在纤维素酶基因完全诱导中的差异参与，表明TrGAL11是大多数纤维素酶基因有效转录起始所必需的。此外，我们发现TrGAL11募集到纤维素酶基因启动子的过程很大程度上以XYR1依赖性方式发生。尽管在没有TrGAL11的情况下xyr1的表达明显降低，但是XYR1与纤维素酶基因启动子的结合并不需要TrGAL11。这些结果表明TrGAL11代表直接体内 可能是XYR1的靶标，并且可能在介导介体和随后的RNA Pol II募集中起关键作用，以确保诱导的纤维素酶基因表达。