Site specific sorting signals for the seed storage protein accumulation

我们以水稻胚乳细胞发育过程中贮藏蛋白的积累过程为模型系统，研究了植物贮藏蛋白基因表达、生物合成和运输的一般机制。本研究的主要目的是：1)阐明胚乳细胞的分化机制，2)确定贮藏蛋白在内质网膜上的靶向位置，3)鉴定蛋白体II型和糊粉颗粒的膜。结果1)我们克隆了一个在发育非常早期(开花后第3天，淀粉胚乳细胞和糊粉粒细胞尚未分化)特异表达的Rcdl基因。2)在生长蛋白体膜(PB-I)膜和PB膜相邻区域观察到醇溶蛋白的合成。3)液泡膜固有蛋白(TIP)异构体在蛋白体II和糊粉颗粒膜上的分布表明两种细胞器都来自液泡。两种颗粒上尖端异构体的不同组合表明，这些细胞器存在着不同的发育过程。

We studied the accumulation processes of storage proteins in the developing rice endosperm cells as a model system to understand the general mechanisms for the gene expression, the biosynthesis, and transport of plant storage proteins. The major objectives of this study are, 1) To clarify the differential mechanism of the endosperm cell, 2) To specify the targeting site of storage proteins on the ER membrane, and 3) To characterize the membranes of protein body type II and aleurone particle.As the result of 1), we isolated an Rcdl cDNA that is expressed specifically at the very early developing stage ( at the third day after flowering, starchy endosperm cell and aleurone cell are not yet differentiated).2) Prolamin synthesis was observed on the growing protein body I (PB-I) membrane and the adjacent area to the PB membrane. A Myc antibody was used in this investigation.3) The distribution of the tonoplast intrinsic protein ( TIP ) isoforms on the membrane of protein body II and aleurone particle indicated both organelles derived from vacuoles. The different combinations of the TIP isoforms on both particles indicated the different developmental processes are existing to from these organelles.