Many plant seeds are used as food and, with the increase in population, can be expected to assume a greater importance as a source of protein. Although considerable effort has been directed at understanding how the major seed protein genes are regulated in the nucleus, very little is known about the cellular events that control the expression of their RNAs in the cytoplasm. Previous efforts from this laboratory have demonstrated that storage protein RNAs (and many other RNAs) are not immediately translated into protein when they exit the nucleus. Instead, they form large particles which are transported along different pathways to the cortical region, a site conducive for protein synthesis and located underneath the plasma membrane. In this project, an integrated molecular, genetic and cell imaging approach will be employed (1) to define the zip code RNA sequences that confer RNA transport and targeting to the cortical region, (2) to isolate the protein factors that recognize these zip codes and confer transport specificity, (3) to determine the protein and RNA composition of these RNA transport particles, and (4) to identify the genes in several rice mutants defective in RNA transport. This study will provide new insights into how RNAs and, in turn, proteins are localized and accumulated in plant cells. Moreover, it may lead to new insights into the mechanisms that control the utilization of carbon and nitrogen and their conversion into storage reserves and, thereby, aid in efforts to increase seed quality and crop productivity. The project will serve to train young scientists at the postdoctoral, graduate and undergraduate levels and will provide these younger scientists the opportunity for international research. The project will also aid in further developing a lecture course on protein targeting in eukaryotic cells taught by the P.I., and will strengthen an ongoing international collaborative study on the genetic, biochemical and cellular aspects of seed quality and yields.
