Role of Amino Acid Transporters in Seed Development

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Assimilate distribution (partitioning) in plants is hypothesized to be regulated by transport processes located in importing organs (sinks) such as developing seeds. The transport of amino nitrogen, in particular, is a major factor influencing plant productivity, crop yield and reproductive success. However, key nitrogen transport processes remain to be identified and characterized. This project utilizes a multidisciplinary approach to characterize amino acid transport processes in sink tissues and specifically to determine the function of amino acid transporters expressed in reproductive structures. The overall goal is to understand, at a cellular and molecular level, the role of amino acid transporters in controlling nitrogen transport to and within seeds. Using Arabidopsis fruits (siliques) and seeds as a sink model, we intend (1) to identify the cellular and subcellular localization of members of the amino acid transporter family that are expressed during silique/seed development, (2) to understand mechanisms controlling amino acid transport in sinks by characterizing the physiological and molecular regulation of amino acid transporters, and (3) to assess the functional significance of amino acid transporters in controlling import of organic nitrogen into developing seeds using molecular genetic manipulation of transporter expression and activity. The information obtained from the proposed work will form the basis for understanding the function of various amino acid transporters in nitrogen transfer and partitioning to and among seed tissues. In addition, it will provide a platform for more detailed future studies to evaluate transporter contribution to nutrient accumulation by seeds in other plant species. The program will also offer a framework for the development of biotechnological innovations to increase crop yield and for modifying nutritional qualities of seeds with respect to their amino acid complement.