Subcellular mRNA localization and translational control in plant cells

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The subcellular localization of mRNAs is an important post-transcriptional regulator of gene expression that has critical roles in cellular function and in development. mRNA localization is essential in establishing spatial patterning during development, facilitating targeting of proteins to organelles, and generating cellular polarity. Although mRNA localization is well studied in animal and fungal cells, very little is known about the process in plant cells. My research program is aimed at providing a deeper understanding of mRNA localization and its associated translational control in plant cells. Three research objectives related to mRNA localization and translational control are described in this proposal. The first objective describes experiments that are aimed at determining the role of AtPum6, an Arabidopsis Puf RNA-binding protein, in mRNA localization to the endoplasmic reticulum (ER). The goals are to confirm the localization of AtPum6 to the ER, identify the mRNAs that bind to AtPum6, and study the subcellular localization and transport of these mRNAs. The second objective is aimed at elucidating the role of the microtubule and RNA binding activities of peroxisomal matrix proteins. We hypothesize that these cytosolic activities are important in the autoregulated translation and import of these proteins in association with the cytoskeleton. To test this hypothesis we will determine the effect of cytoskeleton disruption on the synthesis and import of peroxisomal matrix proteins, and we will identify mRNAs that bind to these proteins in vivo. In the third objective, we will determine the role of an exon-junction complex (EJC) associated protein called PYM (Partner of Y14 and Mago) on translation initiation in plant cells. PYM interacts with the EJC in mammalian cells to recruit the small ribosomal subunit and facilitate the initiation of translation. A translation initiation role for PYM in plant cells may serve to de-repress translation of localized mRNAs at their final destination in the cell. Overall, these experiments will provide important insight into the process of mRNA localization and translational control in plant cells.