油菜重要候选基因BnaA9CHLSYN对籽粒维生素E合成产生关键性作用的分子机制研究

Vitamin E, is an essential active compund for human being and animals, which can't be synthesized by themselves. Among the global demands for fourty thousands tons of vitamin of each year, only 10% of them comes from the natural resouces.Due to their higher activity, the global demands for this limited resource of natural vitamin E,which mainly comes from vegetable-oil industrial production, is increasing by years. Being one of the most important resources for natural vitamin E production in the world, Rapeseed is regarded as the most potential oilcrops which could meet this demands in China. However, the goals targeting for enhancing the tocopherol form of vitamin E, which is widely occurred in nature and most active form readily to be abosorbed by our bodies, is still undergoing.The bottleneck, which limits further enhancing tocopherol content in those green tissues such as rapeseed seeds, is the result of low availability of substrate PDP as revealed in our previous experiment in which most of PDP generated from the chlorophyll breakdown process was recycled by chlorphyll synthase (CHLSYN). To break up this limiting step, a series of natural Rapeseed resouces with significant variations on their tocopherol content, is proposed to be used for identifying putative advantageous alleles, which featured by reduced affinity to substrate PDP without the expense of chlrophyll biosynthetic efficiency. The biochemical basis of tocopherol biosynthesis could be revealed through this project.

油菜是我国最重要的油料作物之一，是天然维生素E（VE）的主要来源。油菜籽VE(生育酚)合成主要通过叶绿素分解途径，但籽粒发育过程中合成毫克级叶绿素而种子成熟后仅生成微克级生育酚，说明发育过程中叶绿素分解产物向生育酚转化效率存在严重障碍。本研究拟以生育酚含量存在明显差异的油菜籽粒为研究对象，在我们前期探明拟南芥叶片内叶绿素合成酶是限制叶绿素分解产物向生育酚高效转化的根本原因，以及关联分析（GWAS）结论认为A9染色体上叶绿素合成酶是控制不同油菜籽粒生育酚含量变异的位点内重要候选基因的基础上，重点进一步研究不同种子在发育过程中叶绿素合成酶关键候选基因BnaA9CHLSYN表达量或所编码酶活性分别对生育酚合成底物PDP竞争能力的差异研究，进而明确该基因在籽粒内限制叶绿素向生育酚高效转化中的作用及其生化与分子机制，为生产高VE含量的油菜分子育种提供理论依据。

油菜种子富含维生素E，在维持人和动物正常生命活动中发挥着至关重要作用。，本项目研究以油菜的近缘种拟南芥为模式植物，对维生素E合成代谢的调控模式进行了研究，，拟南芥籽粒叶绿素合成酶(Chlorophyll synthetase，CHLSYN)可与AtHPT（拟南芥尿黑酸植基转移酶，是控制生育酚合成的限速酶）共同竞争底物PDP，是影响生育酚合成的重要限制性因子，在干扰降低叶绿素合成酶基因表达量的基础上，进一步超量表达提高维生素E合成前体物质尿黑酸的合成，并超量表达维生素E合成的关键酶基因AtHPT，打破了维生素E（生育酚）含量的世界记录，解释了生育酚和生育酚三烯相对含量形成的生化基础。总之，本研究的开展为创建具高含量维生素E的油菜种质提供了重要理论基础。