Protein Targeting and Vesicular Trafficking
Washida, Haruhiko , Sugino, Aya , Kaneko, Sachiyo , Okita, Thomas W .
Identification of zip codes that target rice glutelin RNA to the cisternal ER.
RNAs for the rice storage proteins, prolamines and glutelins, are segregated to specific ER subdomains. Prolamine mRNAs are localized to the ER membranes (PB-ER) that delimit the prolamine protein bodies (PBs), whereas glutelin RNAs are distributed on the cisternal ER. Ongoing studies have shown that these RNAs are targeted to these ER subdomains by RNA transport pathways requiring specific RNA zip code sequences with the glutelin signals functionally dominant to the prolamine signals. We set out to identify the glutelin zip codes by their capacity to re-direct the localization of a maize 10 kD zein RNA (which contains multiple PB-ER zip codes) to the cisternal ER. Analysis of transgenic rice plants expressing various hybrid zein-glutelin RNAs by in situ RNA localization analysis showed that the glutelin transcript contains at least three cisternal ER targeting zip codes. One zip code is located within exon 1, while two lie within exon 4 which includes the 3'UTR. In addition to RNA localization, we also studied where the zein polypeptides were deposited in these various transgenic plants. Immuno-cytological studies at the light and electron microscopy levels demonstrated that when the zein RNAs were targeted to the PB-ER their proteins were stored within the prolamine PBs. When the zein RNAs were targeted to the cisternal ER, however, the proteins were observed within the protein storage vacuoles (PSVs). Our result indicates a close relationship between RNA and protein localization and provides the underlying basis for the variable use of the ER lumen or PSV as the site of storage protein deposition among flowering plants.
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1 - Washington State University
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM