高粱RAP2基因在细胞壁合成中的功能研究和机制探索

The development of bioethonal from cellulose, which will not threaten food supplies, is significant for bioenergy production. In order to achieve cost-effective conversion, the feedstock quality needs to be genetically improved, particularly reducing lignin concentration and increasing cellulose content. Sorghum (Sorghum bicolor L.), with higher photosynthesis efficiency and biomass yield, abundant germplasms and excellent tolerance to drought and salinity, has been recommended as one of the most competitive bioenergy crops. Moreover, the sorghum genome is smaller and has been sequenced. Brown midrib (bmr) mutant sorghums with reduced lignin content showed a high potential for the improvement of bioethanol conversion efficiency. Suppression subtractive hybridization (SSH) combined with cDNA microarray profiling was performed to identify the differentially expressed genes in sorghum bmr mutants and a total of 153 differentially expressed genes were identified. Among the differentially expressed genes, a transcription factor gene SbRAP might be involved in lignin synthesis regulation. For validating the function of SbRAP in lignin synthesis regulation, we will overexpress and RNAi knock-out SbRAP in Arabidopsis and sorghum respectively, and detect their lignin and cellulose content. The influence of SbRAP to the structure and growth of the transgenic plants will also be observed. The proteins interacted with SbRAP will be screened through yeast-two hybridization and the down stream target genes of SbRAP will also be exploited. This work will provide new resources for genetic improvement of lignocellulosic biomass with improved bioethanol production and technical support for energy sorghum improvement.

发展纤维素乙醇工程，不影响粮油食品安全，对生物能源产业意义重大。低木质素、高纤维素原料可提高纤维素酶的降解效率，降低生产成本，是该技术产业化的基础。高粱光合效率高，耐盐碱，生物量大，基因组较小且测序已经完成，有丰富的资源，是很有潜力的能源作物。黄中脉突变体（brown midrib,bmr）茎叶木质素含量明显降低，是研究细胞壁木质素合成代谢的良好材料。前期通过抑制性差减文库和基因芯片技术试验，发现高粱bmr突变体与对照有153个基因差异表达，从中筛选出与木质素合成调控的相关转录因子SbRAP。本研究拟构建过表达和RNAi载体，转化拟南芥和高粱，检验转化体细胞壁中木质素和纤维素的含量和对其结构及生长发育的影响，验证目标基因的功能；同时通过酵母双杂交等技术识别其相互作用蛋白，研究其控制的下游靶基因及其可能的作用机理，为利用基因工程和分子标记辅助育种方法培育优质高产的能源高粱提供技术支撑。