Genetic mechanism controlling the transportation and accumulation of glutelin into protein body in rice endosperm

为了阐明水稻种子贮藏蛋白在细胞内运输和积累的机制，共产生了130个57H突变体，其特征是57H蛋白含量增加57kD，并鉴定出4个新的57H性状基因。在对突变体进行遗传学和组织化学分析的基础上，讨论了每个基因的功能：内质网储存蛋白的分选突变，类型1突变。ESP2突变缺失PDI的分析表明，PDI对于内质网储存蛋白前体和醇溶蛋白的分选是必不可少的。GLUP4和GLUP6突变也被归类为1型突变，表明至少有3个基因参与了内质网腔内这两种蛋白的分选。-从内质网运输到蛋白质储存空泡(PSV)的突变，2型突变中的2型突变，Proglelin前体和醇溶蛋白在内质网来源的PB中积累成独立的颗粒。GLUP1、GLUP2、GLUP5、GLUP7、GLUP8突变被归类为2类突变，表明至少有5个基因参与了原谷蛋白从ER腔到PSV的运输。-PSV内蛋白降解突变。类型3突变对Glup3突变的分析表明，VPE对于PSV内蛋白前体的蛋白水解性切割是必不可少的。这些结果表明，谷蛋白在种子中的运输和积累是分步骤进行的，每一步的调控基因是：1)谷蛋白mRNA靶向顺式内质网，2)内质网内谷蛋白前体的分选，ESP2(PDI)，Glup4，Glup6，3)蛋白前体进入PSV，Glup1，Glup2，Glup5，Glup7，Glup8，4)蛋白前体在PSV内的蛋白分解，Glup3(VPE)，

To elucidate the mechanism of intracellular transportation and accumulation of rice seed storage protein, 130 Iines of 57H mutant, which are characterized by the increased amount of proglutelin with 57 kD, were produced and novel 4 genes for 57H trait were identified. Based on genetic and histochemical analyses of the mutants, the function of each gene was discussed.-Mutation for the sorting of storage proteins within endoplasmic reticulum (ER), Type1 mutation The analysis of esp2 mutation deleted PDI demonstrated that PDI was indispensable for the sorting of proglutelin precursor and prolamin within ER Iumen. glup4 and glup6 mutations also were classified into Type1 mutation, showing that at least 3 genes participate in the sorting of both proteins within ER lumen.-Mutation for transportation from ER to protein storage vacuole (PSV), Type2 mutation In Type2 mutation, proglutelin precursor and prolamin were accumulated into separated particles within ER derived PB. Glup1, glup2, Glup5, glup7, Glup8 mutations were classified into Type2 mutation, showing that at least 5 genes participate in the transportation of proglutelin from ER lumen to PSV.-Mutation for proteolysis within PSV. Type3 mutation The analysis of glup3 mutation demonstrated that VPE was indispensable for proteolytical cleavage of proglutelin precursor within PSV. glup3 mutation accumulated the progiutelin and the cleaved form of glutelin in PSV together, showing that at least 2 VPEs participate in proteolysis of proglutelin precursor.These results demonstrated that the pathway of transportation and accumulation of glutelin in seed was divided into steps and that the genes regulating each step were 1) Targeting of glutelin mRNA to cis-ER, 2) Sorting of proglutelin precursor within ER lumen, Esp2 (PDI), Glup4, Glup6, 3) Transportation of proglutelin precursor into PSV, glupl, Glup2, glup5, Glup7, glup8, 4) Proteolysis of proglutelin precursor within PSV, Glup3 (VPE),