信号感应传递在微生物应对环境营养物变化过程中发挥着重要作用。丝状真菌瑞氏木霉具有在纤维素条件下快速大量合成纤维素酶的重要生物学特性，但其精确的诱导物感应与传导机制并不清楚。细胞膜蛋白受体是起始信号感应传递的重要组分，深入阐释膜蛋白受体在纤维素酶诱导合成中的作用机理有助于全面深化对瑞氏木霉纤维素酶调控体系的认识。本项申请拟围绕前期鉴定的瑞氏木霉纤维素酶基因诱导表达必需的类转运蛋白受体Crt1，系统研究其信号感应与传递机制。利用酵母膜蛋白杂交体系筛选鉴定与Crt1相互作用的下游效应因子；解析二者相互作用的结构基础；结合Crt1与诱导物配体识别的结构特征探究，系统分析下游效应因子及其与Crt1相互作用的变化对纤维素酶靶基因转录表达的影响及影响机制，明晰Crt1信号传递的相关途径机理。研究结果将不仅拓展真核生物类转运蛋白受体的结构功能研究，还将为构建高产纤维素酶菌株或提高酶生产效率提供理论依据。

Signal sensing and transduction play a key role in microbes coping with the extreme changes in the availability of nutrients including carbon sources in their living environment. Filamentous fungi Trichoderma reesei is characterized by its outstanding ability to rapidly initiate the launching of cellulase biosynthesis in the presence of cellulose substrates which otherwise are kept silent. This important biological characteristic is also of industrial relevance as T. reesei has been developed into one of the workinghorses for protein production. Unfortunately, the precise mechanism underlying the inducer recognition and the ensuing signal transduction is not clear yet. Receptors on the plasma membrane are usually the first choice to initiate the signal sensing and transducing. Understanding the detailed mechanisms by which membrane receptors are involved in regulating the induced synthesis of cellulases in T. reesei will provide deeper insights into the regualtion system for T. reesei cellulases . The present application aims to focus on our recently identified sugar transceptor Crt1, which is essential for the induced cellulase gene expression. Systematic studies will be carried out to elucidate how it recognizes the inducer and transduces the activating signal. Attempts will first be made to screen for and verify downstream effectors interacting with Crt1 using yeast screening system for membrane proteins. In combination with structural bioinformatics, interactions between Crt1 and the inducer ligand as well as the effectors would be thoroughly dissected to provide structural information for inducer recognition and pathways for signal transduction. The effects of change in Crt1-inducer interaction on the Crt1-effector interaction and on the final induced expression of cellulase genes will be analyzed systematically. The results are anticipated not only to extend the structural and functional understanding on eukaryotic transceptors, but also to help design highly efficient inducing strategy, or to genetically engineer T. reesei strains to improve their productivity of cellulases/hemicellulases, thus lowering the cost of biomass conversion.