Cell Res：中国学者利用CRISPR技术解析水稻灌浆

　　

　水稻胚乳是人类最主要的粮食来源之一，其结构包含内侧的淀粉胚乳和外侧的糊粉层。叶片光合作用产生的碳水化合物主要以蔗糖形式从筛管组织运输到籽粒。前人的研究认为蔗糖在到达籽粒之后先分解成果糖和葡萄糖，然后通过单糖转运蛋白运输至淀粉胚乳进而合成淀粉。蔗糖是否直接进入、如何进入淀粉胚乳的机制一直不很清楚。

　　近日，中国科学院植物研究所刘春明研究组利用芯片杂交、荧光定量PCR和原位杂交等实验发现了一个在水稻籽粒背侧糊粉层特异表达的转录因子OsNF-YB1，并通过CRISPR-Cas9和RNAi等技术对该基因进行了敲除和表达干扰，发现OsNF-YB1直接调控水稻的灌浆和淀粉累积，并且OsNF-YB1敲除突变体籽粒中的蔗糖、葡萄糖和果糖含量均大幅度下降。进一步生化分析发现OsNF-YB1通过直接结合于三个蔗糖转运蛋白OsSUT1、OsSUT3和OsSUT4的基因表达调控区来调控蔗糖直接进入胚乳。

　　该研究成果对于理解禾本科作物的灌浆机理具有重要意义，有可能为提高作物产量提供新工具。

　　该成果于9月25日在线发表于Cell Research 期刊上。刘春明研究组博士研究生白爱宁为论文第一作者。研究得到了中国科学院-澳大利亚联邦科学与工业研究组织合作研究计划、国家“863”项目和国家转基因科学和技术项目的资助。

模式图：OsNF-YB1激活蔗糖转运蛋白的基因表达，调控水稻灌浆

原文摘要：

NF-YB1-regulated expression of sucrose transporters in aleurone facilitates sugar loading to rice endosperm

Cereal endosperms, which consist of an outer aleurone layer and an inner starchy endosperm, provide over 70% staple food for human [www.fao.org]. Rice endosperm development occurs in the caryopsis of a grain. During the grain filling stage, sucrose produced in photosynthetic leaves is transported to grains via the phloem1,2. It has been proposed that sucrose, upon arrival in the caryopsis through the phloem located at the dorsal vascular bundle, is partially hydrolyzed by cell wall invertases (CINs) into glucose and fructose3,4. Since endosperm is symplastically isolated from maternal tissues, it is assumed that these sugars are delivered to the endosperm actively through an apoplastic pathway by sugar transporters located in aleurone5,6. However, the exact role of aleurone in regulating sugar transport remains unknown.