转录因子BEAR1调控水稻耐盐性的分子基础

水稻耐盐基因的挖掘及调控网络解析是水稻耐盐分子育种的基础。通过大规模筛选盐胁迫响应的转录因子并经人工miRNA干扰材料的田间耐盐性鉴定，我们发现bHLH类转录因子BEAR1参与水稻耐盐性的调控。盐胁迫处理下，BEAR1干扰株系及CRISPR株系均有明显的盐敏感表型，生理生化指标表明BEAR1正向调控水稻耐盐性。我们鉴定了BEAR1的转录激活活性以及活性位点，通过酵母双杂交文库筛选，我们鉴定到了BEAR1的调控蛋白BIP1，BIP1是蛋白泛素降解途径的重要组分。BIP1的CRISPR材料表现出耐盐表型，说明BIP1也参与水稻的盐胁迫反应。本项目拟在以上研究的基础上，分析BEAR1与BIP1相互作用的生化基础，解析BIP1通过泛素降解调控BEAR1的分子途径，构建bear1 bip1双突变体并剖析BEAR1-BIP1模块调控水稻耐盐性的遗传调控网络，为水稻耐盐新材料的创建提供基因资源和基础。

Agriculture is the primary industry and the foundation of the world. Fundamental prerequisite of assurance of food security is the protection of arable land. The salinization of soil is one of the most important environmental factors affecting the yield of crops. Crop salt-tolerance molecular breeding which improves the yield of crops in salinized soil has realistic significance for rural economic development and ecological environment protection. Rice, which is a moderate salt-sensitive crop, can be affected under salt stress at many aspects including germination, seedling growth, leaf photosynthesis, tillering, flowering phase and seed filling. Discovering rice salt-tolerance gene and analysis its genetic regulation network are the main route of rice salt-tolerance molecular breeding..By large-scale screening of salt-response transcription factors and conformation of salt-tolerance phenotypes in the fields by artificial miRNA transgenic plants, we identified that rice transcription factor BEAR1 participates in regulation of salt-tolerance in rice. Under salt stress condition, BEAR1 knock-down transgenic plants showed significant salt sensitive phenotypes. By examining the physiological and biochemical indicators, we confirmed that BEAR1 positively regulates rice salt tolerance. The BEAR1 functions in salt response were confirmed by salt tolerance analysis with BEAR1 CRISPR plants. The expression levels of many salt response genes and pathways are changed in BEAR1 CRISPR transgenic rice. Following the construction of BEAR1 promoter-GUS plasmid and transformed into rice japonica. cv. Nipponbare, BEAR1 temporal and spatial expression patterns were examined. Transcription activator activity of BEAR1 was proved and the activator function domain and sites were mapped. To find interacting proteins with BEAR1, yeast two-hybrid screening was performed and BIP1 (BEAR1 interacting protein 1), which is a critical component of 26S ubiquitin-proteasome proteolytic pathway, was isolated and confirmed. Furthermore, we created BIP1 CRISPR lines and checked the phenotype of salt tolerance under salt treatment, which indicated that BIP1 play roles in rice salt responses..Based on the above study results, this project will analyse the biochemical mechanism of BEAR1-BIP1 interaction, reveal molecular pathway of BIP1 controlling BEAR1 by ubiquitin-proteasome proteolysis, generate bear1 bip1 double mutant and discover the molecular and genetic network of BEAR1-BIP1 module regulating rice salt tolerance, provide gene resources and theory basis for rice salt-tolerance molecular breeding.