玉米纹枯病菌的一种45家族内切纤维素酶EG1能够诱导植物细胞过敏性死亡、植物防卫反应基因表达、活性氧产生、培养基碱化、钙离子积累、乙烯合成等植物防卫反应，表现为典型的激发子功能，并且它的激发活性与酶活性没有关系。为了进一步理解真菌纤维素酶EG1与植物互作的分子机制，证明纹枯病菌纤维素酶EG1是一种MAMP分子，需要分离和鉴定它的受体蛋白。本项目以玉米与纹枯病菌为研究体系，利用玉米Mu转座子插入突变和MuTail-PCR技术，分离纹枯病菌纤维素酶EG1的受体蛋白基因；利用酵母双杂交、双分子荧光互补、动物细胞表达与结合、免疫沉淀技术，证明真菌纤维素酶EG1与玉米受体蛋白的互作关系；利用受体蛋白基因沉默、互补和超表达技术，进一步证明受体蛋白的生物学功能；利用受体蛋白在洋葱和烟草细胞的瞬时表达，确定受体蛋白的亚细胞定位。研究为植物与病原真菌纤维素酶互作的新机制提供证据。

Plant pathogenic fungi produce cellulases. However, little information is involved in cellulase as an elicitor in plant-pathogen interaction. An endocellulase (EG1) isolated from Rhizoctonia solani induced cell death in maize, tobacco and Arabidopsis leaves, and transcription of three defense-marker genes in maize and tobacco and 10 genes related to defense responses in maize. Moreover, it also induced accumulation of reactive oxygen species, medium alkalinization, Ca2+ accumulation and ethylene biosynthesis of suspension-cultured tobacco cells. Using analysis of elicitor responses for studying elicitor-plant interaction along with the mutational analysis and the PVX expression system, we demonstrated that the EG1 was an elicitor but its elicitor activity was independent of its enzymatic activity. How plant cells recognize EG1 is not understood. We hypothesize that the elicitor activity of the EG1 may be based on the specific recognition between the EG1 elicitor and a possible potential protein receptor in plants. To further understand molecular mechanism of interaction between EG1 and plant and to demonstrate the EG1 elicitor to be an MAMP (Microbe-Associated Molecular Pattern), a mutant library from maize B73 will be constructed by Mutator (Mu) transposon. From the mutant library, the possible potential protein receptor will be isolated using MuTail-PCR. Using analysis of yeast two-hybrid, bimolecular fluorescence complementation, binding between EG1 and mammalian COS-7 Cells overexpressing receptor and coimmunoprecipitation, we will demonstrate their binding between the EG1 and the possible potential protein receptor. With technology of gene silencing, complementation and overexpression, we will further demonstrate the biological function of the possible potential protein receptor and the interaction between the EG1 and the possible potential protein receptor. To examine cellular distribution of the possible potential protein receptor, we will fuse it with green fluorescent protein and be then transformed into onion and epidermal tobacco cells for its transient expression. This project will provide a new mechanism of interaction between fungal cellulase and plants.