Sorting of storage protein mRNAs on distinct endoplasmic reticulum membranes in developing rice endosperms
1996
Muench, D.G. | Zhang, Y. | Wu, Y. | Okita, T.W.
Electron microscopic studies reveal that rice endosperm cells contain two types of endosplasmic reticulum (ER), the cisternal ER (C-ER) and protein body ER (PB-ER). As demonstrated by biochemical techniques and in vitro and in situ hybridization, mRNAs that code for the prolamine storage proteins are enriched up to 10-fold over the mRNAs that code for the glutelin storage proteins on the PB-ER, whereas glutelin mRNAs are about 2-fold more abundant than prolamine mRNAs on the C-ER membranes. Therefore, the initial targeting of glutelins and prolamines into separate protein bodies is facilitated by the segregation of their transcripts on the two distinct ER types. We have obtained evidence suggesting that at least one process that is responsible for targeting of the prolamine mRNA to the PB-ER is the interaction of the prolamine transcript with a receptor on the PB surface. In addition to these studies, we discuss our current efforts to obtain more direct evidence for the mechanism of sorting by generating transgenic plants containing hybrid gene constructs
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