Amino acids play a central role in plant metabolism: their synthesis is tightly linked to carbohydrates; they are used for synthesis of protein and many secondary metabolites; and they are a major transport form of assimilated nitrogen between the organs of the plant, translocated through the phloem and xylem. Consequently, amino acid metabolism and transport needs to be finely tuned to carbon and nitrogen availability, and to demand from the growing organs. My laboratory studies the molecular mechanisms controlling the activity of amino acid metabolism and transport in plants. We want to understand (1) how amino acids are transported across membranes at the subcellular and plant levels, (2) how cells sense amino acid levels inside the organelles and the apoplasm, and (3) how are the signals transduced to changes in metabolic and transport activity. This knowledge would open ways to engineer nitrogen fluxes in the plant, for example diverting resources to specific organs, which would enable to create crops with higher protein in storage organs like seeds, roots or tubers, or plants with increased nitrogen use efficiency.
We use a large set of techniques, including genetics, biochemistry, molecular biology, metabolomics, confocal microscopy, RNAseq, heterologous expression in yeast and Xenopus oocytes to identify and characterize these processes. We mainly use Arabidopsis as a model plant because of the capability for large scale genetic screening, genetic resources and metabolic analyses. We are also working with soybean, in collaboration with Dr. Saghai Maroof (CSES, Virginia Tech).
About 100 amino acid transporters have been identified in Arabidopsis genome, but the roles of only ~15 of them are known. The identity of the transporters mediating amino acid export from the cells is especially lacking. Through a collaboration with Dr. Okumoto (Texas A&M) we characterized members of the UMAMIT family of amino acid exporters and showed that one of them is involved in exporting amino acids from the phloem sap in the roots. Another project focuses on the characterization of the GDU family of genes from Arabidopsis. The GDU proteins associate with the membrane-bound ubiquitin ligases LOG2 and LULs to control amino acid export activity at the plasma membrane and ABA responses. By analogy to animal models, we think the corresponding GDU-LOG2/LUL complexes are regulators of membrane protein trafficking and/or activity at the level of the endosomes.
A lot is known about how amino acids are synthesized and degraded, and how metabolic enzymes are regulated by feedback inhibition. Comparatively, we know little about the regulatory mechanisms controlling the expression of the corresponding genes. More precisely, we do not know what are the proteins sensing amino acid concentrations and transducing the signals, and the downstream regulators. One of the goals of my laboratory is to address this gap in our knowledge by finding some of the genes involved in these processes using genetics.
We are studying how plant amino acid transporters are used by biotrophic pathogens for their nutrition in collaboration with Dr. McDowell (PPWS, Virginia Tech). For this purpose, we use the Hyaloperonospora arabidopsidis / Arabidopsis pathosystem as a model. Other information on oomycete pathogens is available on Dr. McDowell’s page. We are testing the hypothesis that pathogen effectors are changing the expression (level of expression and subcellular localization) of plant amino acid transporters, to divert the amino acid fluxes towards the pathogen feeding structures. In addition to traditional genetic approaches, we are modifying the Translating Ribosome Affinity Purification method to identify the set of genes expressed in the cells in contact with the pathogen. On the long term, the outcomes of this project will help develop new strategies for creating plants that are more resistant to pathogens, by preventing the pathogen to acquire nutrient from the plant, thereby suppressing its growth.
Ph.D. University of Montpellier, Montpellier, France, 1999.
M.S. University of Lyon, Lyon, France, 1996.
B.S. University of Lyon, Lyon, France, 1995.
- 2016-present: Associate Professor, Virginia Polytechnic Institute and State University, Blacksburg, VA.
- 2009-2016: Assistant Professor, Virginia Polytechnic Institute and State University, Blacksburg, VA.
- 2007-2009: Postdoctoral Research Associate, Carnegie Institution for Science, Stanford, CA.
- 2005-2006: Postdoctoral Research Associate, IZMB, Bonn, Germany.
- 2002-2004: Postdoctoral Fellow, ZMBP, Tuebingen, Germany.
- 2000-2001: Research Scientist, Aventis CropScience, RTP, NC.
- 1996-1999: Graduate Student, INRA Montpellier, Montpellier, France.
Selected Major Awards
- 2002 European Molecular Biology Organisation (EMBO) Postdoctoral Fellowship (2 years)
- PPWS / BCHM 5344 – Molecular Biology for the Life Sciences
The Pilot lab has participated in the Partnership for Research and Education in Plants program since 2010. PREP brings together research groups and high-school students to perform actual experiments on generally poorly characterized Arabidopsis mutants. For example, over the course of the last 6 years the Pilot lab has provided three teachers (about 250 students) with the seeds of the gdu1-1D mutant, which displays alteration in AA export. Seeds of other mutants isolated in the lab are also used. With input from the PI, the students choose with their teacher the growth conditions to compare the wild type and the mutant. The researchers stay in contact with the teacher and the students by email and come in person to meet with the students, talk about the progress of the experiment and the encountered problems, with the goal of teaching the principle of hypothesis-driven methodology of scientific research. At the end of the experiment the students prepare a short presentation of their results and present them to the researchers, the classroom and the teacher.
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