An amino acid transporter plays a regulatory role in amino acid homeostasis in plants: evidence for a new transceptor?

Dr. Pilot completed his Ph.D. in France, studying the role of potassium channels in Arabidopsis thaliana. His post-doctoral work in Germany and in California led him to characterize novel proteins involved in the regulation of amino acid export from plant cells. Since joining Virginia Tech in 2009, Dr. Pilot’s work has focused on the study of amino acid transporters in plants and their role in controlling amino acid homeostasis. The techniques used in his laboratory are diverse, involving physiology, forward and reverse genetics, imaging, molecular biology and biochemistry. The research subjects in the group span from basic understanding of the function of the many amino acid transporters from Arabidopsis to exploring the role of amino acid transport in the determination of seed protein content in soybean or how it is highjacked by pathogens to extract nitrogen from plant cells. This research shows that membrane transport of amino acids is integral to metabolic pathways as it controls nitrogen exchange and signaling between organelles and between cells in plants.

Amino acid metabolism activity is finely tuned to carbon and nitrogen availability and to the demand of organic nitrogen from the growing organs. Although the activity of amino acid metabolic pathways is regulated at the transcript, translational and post-translational levels, nothing is known about the earlier steps of the regulation cascade, namely amino acid sensing and signaling in plants. In yeast and mammals however, amino acid sensing has been shown to involve several sensors, some of which are also membrane transporters and therefore called transceptors. Our work focuses on Amino Acid Permease1 (AtAAP1) from Arabidopsis, one of the best characterized amino acid transporter in plants. Our recent - physiological characterization of point mutation mutants suggests that AtAAP1 is involved either directly or indirectly in amino acid sensing, and that disruption of AtAAP1 functions affects amino acid homeostasis. At least one of these mutations seems to uncouple sensing from transport, leading to the hypothesis that AtAAP1 is an amino acid transceptor.

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