Guillaume Pilot

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 that control 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 their amino acid content, and (3) how are the signals transduced to make 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, enabling the creation 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 and transcriptomics.

Current Projects

1. Much is known about how amino acids are synthesized and degraded, and how metabolic enzymes are regulated by feedback inhibition. Yet, evidence suggest other still undefined mechanisms are controlling their activity, acting at the transcript and protein levels. In particular, we do not know which proteins are sensing amino acid concentrations and transducing the signals. One of the goals of my laboratory is to address this gap in our knowledge by finding and characterizing genes involved in these processes. We are currently working on a membrane protein that appears to have both amino acid transport and sensing function, i.e. a transceptor. We are also trying to understand the relationships between the protein kinase Target of Rapamycin (TOR) and ABA signaling in the regulation of amino acid metabolism. Understanding how amino acids are sensed by the transceptor and TOR, and how this information is used by the plant to promote or restrict growth would help create plants with optimized nitrogen use in field conditions or increase tolerance to stress.
2. Protein hydrolysates have been shown to stimulate growth on crops when sprayed at low concentration. My laboratory is interested in understanding which processes are affected by this class of biostimulants, in order to predict the best application regime and timing. We are also collaborating with various laboratories to test the effect of protein hydrolysate-based biostimulants on crops (e.g. corn, soybean, strawberry, tomato), to help Virginia farmers lower their use of synthetic fertilizers while achieving similar yield.
3. We are studying how plant amino acid transporters are used during infection by pathogens, namely the oomycete Hyaloperonospora arabidopsidis and the bacterium Pseudomonas syringae, in collaboration with Dr. McDowell. In 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 from acquiring nutrient from the plant, thereby suppressing its growth.
4. Protein content in soybean seed is an important trait that determines seed value for animal feed. While studied for decades, the genes and the processes responsible for this trait have not been identified. We are working with Dr. Saghai Maroof to understand the role of amino acid transport in the determination of the amount of protein stored in the seeds of soybean. We use association mapping of a large variety of lines, transgenesis and physiology to identify and characterize the role of candidate genes.

• 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, N.C.

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

• 2002 European Molecular Biology Organisation (EMBO)
• Postdoctoral Fellowship (2 years)

1. Dinkeloo K., Pelly Z., McDowell J.M., Pilot G. 2022. A split green fluorescent protein system to enhance spatial and temporal sensitivity of translating ribosome affinity purification. The Plant Journal. 111: 304-3015. https://doi.org/10.1111/tpj.15779
2. Zhang X., Khadka P., Puchalski P., Leehan J.D., Rossi F.R., Okumoto S., Pilot G., Danna C.H. 2022. MAMP-elicited changes in amino acid transport activity contribute to restricting bacterial growth. Plant Physiology. https://doi.org/10.1093/plphys/kiac217
3. Zhao C., Pratelli R., Yu S., Shelley B., Collakova E., Pilot G. 2021. Detailed characterization of the UMAMITs proteins provides insight into their evolution, amino acid transport properties, and role in the plant. Journal of Experimental Botany. 72: 6400–6417. http://doi.org/10.1093/jxb/erab288
4. Besnard J, Sonawala U, Maharjan B, Collakova E, Finlayson SA, Pilot G, McDowell J, Okumoto S. 2021. Increased expression of UMAMIT amino acid transporters results in activation of salicylic acid dependent stress response. Frontiers in Plant Sciences. 11: 606-386. http://doi.org/10.3389/fpls.2020.606386
5. 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
6. 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
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