Poster: Membrane Transport
Abs #
1241: Metabolite Regulation of Amino Acid Transporter AtAAP1
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Presenter: |
Guo, Mengjuan , mguo@uiuc.edu |
Authors | Guo, Mengjuan (A) (B) Bush, Daniel (A) (C) | | Affiliations: |
(A): University of Illinois
(B): Program in Physiological and Molecular Plant Biology
(C): Photosynthesis Research, USDA-ARS
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In higher plants, amino acids are the currency of nitrogen exchange between the sites of primary assimilation and the import-dependent tissues. The partitioning of amino acids in this resource allocation process requires the activity of several classes of amino acid transporters in the plasma membrane (BBA - Biomembranes 1465:275). The transcript of AAP1, a proton-amino acid symporter, in mature leaf tissue is regulated by nutrient status and environmental cues. After 7 days nitrogen starvation, AAP1 message is highly induced after feeding 30 min in 25 mM NO3- or 10 mM NH4+ or 5 mM amino acids such as glutamine, glutamate and asparagine. Nitrogen mediated AAP1 message changes may be due to multiple signals. Inhibitors of nitrate reductase, glutamine synthetase, and aminotransferases do not block induction by NO3-, NH4+ and asparagine, respectively, while glutamate synthase inhibitors decrease the induction from glutamine, suggesting the importance of glutamine-glutamate cycle in nitrogen signaling. AAP1 is also induced in dark-adapted plants after 3 hours of illumination. Light dependent changes in expression may be mediated by a specific photoreceptor or by photosynthesis-dependent increases in leaf sugar content. Both 1% sucrose or glucose feeding induces AAP1 message in dark- adapted plants, suggesting light induction might be an indirect effect of sugar-signaling. However, we can not rule out a role for a photoreceptor in regulation of AAP1 message, because far red light illumination decreases the sucrose-dependent induction. Current efforts in the lab include parallel experiments using expression profiling to identify transcription factors associated with changes in AAP1 expression, and developing genetic tools for dissecting this response pathway.
