ABSTRACT
Intracellular m RNA localization is an important regulatory aspect o f eukaryotic gene expression. Targeted, active transport requires RNA cis-localization elements, trans-acting RN A binding proteins (RBPs) that recognize these sequences and an intact cytoskeleton. Although highly prevalent and well-studied in metazoans and yeast, relatively few reports o f RNA localization exist for plants. The asymmetric sorting o f storage protein mRNAs in developing rice endosperm, however, has proven to be an excellent model for study. Proper storage protein synthesis and deposition into separate subcellular compartments requires direct targeting o f the corresponding mRNA to distinct subdomains o f the cortical endoplasmic reticulum (ER). Although evidence supports the existence o f two regulated RN A localization pathways to the ER that are dependent upon RN A cis-localization sequences and cytoskeleton, litde is known about the trans-acting factors required for transport. Much remains to be discovered about plant RBPs in general and the identification and subsequent characterization o f cytoskeleton-associated RBPs and accessory proteins involved in seed storage protein RNA localization will further our knowledge o f cytoplasmic gene expression events.
