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Guillaume Pilot

Associate Professor
Guillaume Pilot
206 Latham Hall 0390
Blacksburg, VA 24061

Overview

My research aims at understanding the molecular regulation of amino acid transport and translocation in plants, focusing on the study of amino acid transporters. I am also interested in deciphering the mechanisms used by pathogens to extract amino acids from plants, and identifying some of the molecular actors controlling protein accumulation in soybean seeds.

Expertise

  • Plant Molecular Physiology

Education

  • Ph.D. University of Montpellier, Montpellier, France, 1999.
  • M.S. University of Lyon, Lyon, France, 1996.
  • B.S. University of Lyon, Lyon, France, 1995.

Program Focus

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).

Current Projects

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.

  • PPWS / BCHM 5344: Molecular Biology for the Life Sciences
  • PPWS 5534: Advanced Plant Physiology and Metabolism II

Associate Professor | 2016-present
Virginia Polytechnic Institute and State University, Blacksburg, Va.

Assistant Professor | 2009-2016
Virginia Polytechnic Institute and State University, Blacksburg, Va.

Postdoctoral Research Associate | 2007-2009
Carnegie Institution for Science, Stanford, Ca.

Postdoctoral Research Associate | 2005-2006
IZMB, Bonn, Germany.

Postdoctoral Fellow | 2002-2004
ZMBP, Tuebingen, Germany

Research Scientist | 2000-2001
Aventis CropScience, RTP, NC.

Graduate Student | 1996-1999 
INRA Montpellier, Montpellier, France.

  • 2002 European Molecular Biology Organisation (EMBO)
  • Postdoctoral Fellowship (2 years)
  1. Sonawala, U., Dinkeloo K., Danna C.H., McDowell J.M., Pilot G. 2018. Review: Functional linkages between amino acid transporters and plant responses to pathogens. Plant Science. 277: 79-88. http://doi.org/10.1016/j.plantsci.2018.09.009
  2. Besnard J., Zhao C., Avice J.C., Vitha S., Hyodo A., Pilot G., Okumoto S. 2018. Arabidopsis UMAMIT24 and 25 are amino acid exporters involved in seed loading. Journal of Experimental Botany 69: 5221-5232. http://doi.org/10.1093/jxb/ery302
  3. Dinkeloo K., Boyd S., Pilot G. 2018. Update on amino acid transporter functions and on possible amino acid sensing mechanisms in plants. Seminars in Cell & Developmental Biology. 74: 105-113. http://doi.org/10.1016/j.semcdb.2017.07.010
  4. Redekar, N., Pilot G., Raboy V., Li S., Saghai-Maroof M.A. 2017. Inference of transcription regulatory network in low phytic acid soybean seeds. Frontiers in Plant Science. 8: 2029. http://doi.org/10.3389/fpls.2017.02029
  5. Lynch J.H., Orlova I., Zhao C., Guo L., Jaini R., Maeda H., Akhtar T., Cruz-Lebron J., Rhodes D., Morgan J., Pilot G., Pichersky E., Dudareva N. 2017. Multifaceted plant responses to circumvent Phe hyperaccumulation by downregulation of flux through the shikimate pathway and by vacuolar Phe sequestration. The Plant Journal. 92: 939–950. http://doi.org/10.1111/tpj.13730
  6. Murphree C.A., Dums J.T., Jain S.K., Zhao C., Young D.Y., Khoshnoodi N., Tikunov A., Macdonald J., Pilot G., Sederoff H. 2017. Amino acids are an ineffective fertilizer for Dunaliella spp. growth, Frontiers in Plant Science. 8: 847. http://doi.org/10.3389/fpls.2017.00847
  7. Guerra D., Chapiro S.M., Pratelli R., Yu S., Jia W., Leary J., Pilot G., Callis J. 2017. Control of amino acid homeostasis by a ubiquitin ligase-coactivator protein complex. The Journal of Biological Chemistry. 292: 3827-3840. http://doi.org/10.1074/jbc.M116.766469
  8. Besnard J., Pratelli R., Zhao C., Sonawala U., Collakova E., Pilot G., Okumoto S. 2016. UMAMIT14 is an amino acid exporter involved in phloem unloading in Arabidopsis roots. Journal of Experimental Botany. 67: 6385-6397. http://doi.org/10.1093/jxb/erw412
  9. Jones A.M., Xuan Y., Xu M., Wang R.S., Ho C.H., Lalonde S., You C.H., Sardi M.I., Parsa S.A., Smith-Valle E., Su T., Frazer K.A., Pilot G., Pratelli R., Grossmann G., Acharya B.R., Hu H.C., Engineer C., Villiers F., Ju C., Takeda K., Su Z., Dong Q., Assmann S.M., Chen J., Kwak J.M., Schroeder J.I., Albert R., Rhee S.Y., and Frommer W.B. 2014. Border control - a membrane-linked interactome of Arabidopsis. Science, 344:711-716. http://doi.org/10.1126/science.1251358
  10. Pratelli R., Guerra D.D., Yu S., Wogulis M., Kraft E., Frommer W.B., Callis J. and Pilot G. 2012. The ubiquitin E3 ligase LOSS OF GDU2 is required for GLUTAMINE DUMPER1-induced amino acid secretion in Arabidopsis. Plant Physiology. 158: 1628-1642. http://doi.org/10.1104/pp.111.191965
  11. Liu G., Ji .Y, Bhuiyan N.H., Pilot G., Selvaraj G., Zou J. and Wei Y. 2010 Amino Acid Homeostasis Modulates Salicylic Acid-Associated Redox Status and Defense Responses in Arabidopsis. The Plant Cell. 22: 3845-3863. http://doi.org/10.1105/tpc.110.079392
  12. Pratelli R., Voll L., Horst R., Frommer W.-B. and Pilot G. 2010. Stimulation of non-selective amino acid export by Glutamine Dumper proteins. Plant Physiology, 152: 762-773. http://doi.org/10.1104/pp.109.151746
  13. Pilot G., Stransky H., Bushey D.F., Pratelli R., Ludewig U., Wingate V.P., and Frommer W.B. 2004. Overexpression of GLUTAMINE DUMPER1 leads to hypersecretion of glutamine from Hydathodes of Arabidopsis leaves. The Plant Cell, 16:1827-1840. http://doi.org/10.1105/tpc.021642
  14. Mouline K., Véry A.A., Gaymard F., Boucherez J., Pilot G., Devic M., Bouchez D., Thibaud J.B., and Sentenac H. 2002. Pollen tube development and competitive ability are impaired by disruption of a Shaker K+ channel in Arabidopsis. Genes & Development, 16:339-350. http://doi.org/10.1101/gad.213902
  15. Gaymard F.*, Pilot G.*, Lacombe B., Bouchez B., Bruneau D., Boucherez J., Michaux-Ferrière N., Thibaud J.-B., and Sentenac H. 1998. Identification and disruption of a plant Shaker-like outward channel involved in K+ release into the xylem sap. Cell, 94:647-655. http://doi.org/10.1016/S0092-8674(00)81606-2

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