343회 mRNA Transport on the ER Subdomain in Rice Endosperm Cells

343회

연사 :  최 상 봉, 한국생명공학연구원

제목: mRNA Transport on the ER Subdomain in Rice Endosperm Cells

Abstract

Selective RNA transport facilitates the rapid protein synthesis in the specific intracellular region of the developing embryo and highly polarized cells such as Drosophila egg and dendrocytes. In plant, although cell-to-cell and long distance RNA transport system that are observed in the RNAs of virus and transcription factors have been studied broadly, intracellular RNA transport has not been investigated. In this presentation, the intracellular transport of rice storage protein RNA is demonstrated. Rice synthesizes and accumulates two major classes of storage proteins, prolamines and glutelins, which are stored in different subcellular compartments of the secretory pathway. Prolamines are deposited directly as spherical protein granules within the ER lumen, whereas glutelins are transported from the ER to the Golgi where they are eventually packaged in protein storage vacuoles. It has been reported previously that prolamine and glutelin RNAs assymmetrically distributed within the cell. To identify the cis-acting element required for the prolamine RNA targeting, transgenic rice plants expressing the modified prolamine RNAs were generated and used for in situ RT-PCR. Fluorescently-labeled signals from the transgenic lines were detected and compared with those from wild-type rice seed sections. Results showed that the transport and targeting of prolamine RNAs to the protein body ER requires specific RNA signal determinants although the presence of an initiation codon is essential. RNA fine mapping result demonstrated that prolamine RNA targeting requires at least two different signal determinants for the targeted localization to the protein body ER. One of the signal determinants is located within the 3' untranslated region and a second one resides on the upstream of coding sequences. Further efforts were made to identify the trans-acting factors that bind to prolamine RNA sequence, and to tract the prolamine RNA movement using GFP-RNA fusion constructs.