Site specific sorting signals for the seed storage protein accumulation

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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.