The aim of our research is to elucidate the molecular mechanisms underlying the regulation of plant morphogenesis via understanding the process of cell shape acquisition and its associated signaling pathways. We are particularly focusing our studies on auxin transport and signaling, endomembrane trafficking and cell wall function in cell shape acquisition. Most of our work is established on the model plant Arabidopsis thaliana but we also work on spruce, poplar and tomato.

Robert Stephanie 1150

Plants have acquired the capacity to grow continuously and adapt their architecture in response to endogenous or external signals, leading to essential morphological adjustments. Morphological changes can be mediated by cell shape acquisition, which is a very complex process in plants due to the presence of a cell wall, located outside the cell’s plasma membrane. The cell wall provides mechanical support and protection to the plant cell and thus needs to be fairly rigid, but also flexible to allow elongation and growth, participating in the determination of plant cell shape and architecture. The phytohormone auxin is an important growth regulator that stimulates cell elongation by inducing wall loosening factors. Importantly, local concentrations of auxin are thought to regulate most aspects of plant development2. The generation of an auxin pattern requires polar auxin transport, which is mediated by the PIN-FORMED (PIN) protein family of auxin efflux facilitators. Auxin action is enhanced by the activity of other classes of growth regulators3, highlighting the importance of small molecules in the control of plant architecture establishment.

Using cell biology, classical genetics and chemical genomics approaches we aim to i) discover new small molecules triggering endomembrane trafficking and signaling events regulating cell expansion, ii) dissect the associated endomembrane trafficking or signaling pathways, iii) understand the link between cell shape determination and cell wall composition.


Figure legend: A) Chemical screening in a 24-well plate. The chemical genomics approach uses small molecules for rapid dissection of biological mechanisms and gene networks in ways not feasible with mutation-based approaches.; B) Confocal microscopy image of Arabidopsis thaliana root- Immunostain labeling of PIN-FORMED 1 (purple) and 2 (blue); C) Confocal microscopy image of Arabidopsis thaliana apical hook - Propidium iodide staining (white) highlights the plasma membrane of epidermal cells; D) Confocal microscopy image of Arabidopsis thaliana leaf pavement cells- The Arabidopsis line imaged expresses an auxin response marker in the nucleus (blue to green/yellow). The plasma membrane is stained with propidium iodide (red).Figure legend: A) Chemical screening in a 24-well plate. The chemical genomics approach uses small molecules for rapid dissection of biological mechanisms and gene networks in ways not feasible with mutation-based approaches (picture: Siamsa Doyle).; B) Confocal microscopy image of Arabidopsis thaliana root- Immunostain labeling of PIN-FORMED 1 (purple) and 2 (blue) (picture: Siamsa Doyle); C) Confocal microscopy image of Arabidopsis thaliana apical hook - Propidium iodide staining (white) highlights the plasma membrane of epidermal cells (picture: Sara Raggi); D) Confocal microscopy image of Arabidopsis thaliana leaf pavement cells - The Arabidopsis line imaged expresses an auxin response marker in the nucleus (blue to green/yellow). The plasma membrane is stained with propidium iodide (red) (picture: Zahra Rahneshan).

Publication list

  1. Cell-surface receptors enable perception of extracellular cytokinins
    Nat Commun 2020, 11(1):4284
  2. Fluctuating Auxin Response Gradients Determine Pavement Cell-Shape Acquisition
    Proc Natl Acad Sci U S A 2020, 117(27):16027-16034
  3. The CEP5 peptide promotes abiotic stress tolerance, as revealed by quantitative proteomics, and attenuates the AUX/IAA equilibrium in Arabidopsis
    Molecular & Cellular Proteomics 2020, 19(8): 1248-1262
  4. Polar expedition: mechanisms for protein polar localization
    Curr Opin Plant Biology 2020, 53:134-140
  5. Chemical screening pipeline for identification of specific plant autophagy modulators
    Plant Physiol. 2019, 181(3):855-866
  6. A role for the auxin precursor anthranilic acid in root gravitropism via regulation of PIN-FORMED protein polarity and relocalisation in Arabidopsis
    NEW PHYTOLOGIST 2019, 223(3):1420-1432
  7. Mechanical Asymmetry of the Cell Wall Predicts Changes in Pavement Cell Geometry
    Developmental Cell 2019, 50 (1), 9-10
  8. FORCE-ing the shape
    Current Opinion in Plant Biology 2019, 52:1–6
  9. A role for the auxin precursor anthranilic acid in root gravitropism via regulation of PIN-FORMED protein polarity and relocalization in Arabidopsis
    New Phytol. 2019 Apr 30 [Epub ahead of print]
  10. Selective auxin agonists induce specific AUX/IAA protein degradation to modulate plant development
    Proc Natl Acad Sci U S A. 2019, 116(13):6463-6472
  11. The Inhibitor Endosidin 4 Targets SEC7 Domain-Type ARF GTPase Exchange Factors and Interferes with Subcellular Trafficking in Eukaryotes
    PLANT CELL 2018, 30(10):2553-2572
  12. New fluorescently labeled auxins exhibit promising anti-auxin activity
    N Biotechnol. 2018, 48:45-52
  13. The Role of Auxin in Cell Wall Expansion
    Int. J. Mol. Sci. 2018, 19(4), 951
  14. Vacuole Integrity Maintained by DUF300 Proteins Is Required for Brassinosteroid Signaling Regulation
    Mol Plant. 2017, 11(4):553-567
  15. Auxin signaling: a big question to be addressed by small molecules
    Journal of Experimental Botany 2018, 69(2):313-328
  16. Mechanochemical Polarization of Contiguous Cell Walls Shapes Plant Pavement Cells
    Developmental Cell 2017, 43(3); 290–304.e4
  17. Regulating plant physiology with organic electronics
    PNAS 
    2017, 114(18):4597-4602
  18. Auxin 2016: a burst of auxin in the warm south of China
    Development 2017 144: 533-540
  19. 2,4-D and IAA Amino Acid Conjugates Show Distinct Metabolism in Arabidopsis
    PLoS One. 2016 Jul 19;11(7):e0159269 eCollection 2016
  20. Mitochondrial uncouplers inhibit clathrin-mediated endocytosis largely through cytoplasmic acidification
    Nature Communications 7, Article number: 11710
  21. Extra- and intracellular distribution of cytokinins in the leaves of monocots and dicots
    N Biotechnol. 2016, 33(5):735-742
  22. Small molecules unravel complex interplay between auxin biology and endomembrane trafficking
    J Exp Bot. 2015, 66(16):4971-4982
  23. Osmotic stress modulates the balance between exocytosis and clathrin-mediated endocytosis in Arabidopsis thaliana
    Mol Plant. 2015 Mar 17. pii: S1674-2052(15)00175-6 [Epub ahead of print]
  24. An early secretory pathway mediated by GNOM-LIKE 1 and GNOM is essential for basal polarity establishment in Arabidopsis thaliana
    Proc Natl Acad Sci U S A. 2015, 112(7):E806-15
  25. Live Cell Imaging of FM4-64, a Tool for Tracing the Endocytic Pathways in Arabidopsis Root Cells
    Methods Mol Biol. 2015;1242:93-103
  26. Unraveling plant hormone signaling through the use of small molecules
    Front. Plant Sci June 2014; 5:373
  27. The cellulase KORRIGAN is part of the Cellulose Synthase Complex
    Plant Physiol. 2014 Jun 19, pp.114.241216
  28. Trafficking modulator TENin1 inhibits endocytosis, causes endomembrane protein accumulation at the pre-vacuolar compartment and impairs gravitropic response in Arabidopsis thaliana.
    Biochem J. 2014; 460:177-185
  29. Using a reverse genetics approach to investigate small-molecule activity
    Methods Mol Biol. 2014;1056:51-62
  30. Auxin biology revealed by small molecules
    Physiol Plant. 2014, 151(1):25-42
  31. The use of chemical biology to study plant cellular processes – subcellular trafficking
    Plant Chemical Biology 22 NOV 2013
  32. ABCG9, ABCG11 and ABCG14 ABC transporters are required for vascular development in Arabidopsis
    The Plant Journal, 2013; 76(5):811-824
  33. ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation
    Proc Natl Acad Sci U S A. 2013 , 110(40):16259-16264
  34. Defining the selectivity of processes along the auxin response chain: a study using auxin analogues
    New Phytol. 2013, 200(4):1034-1048
  35. ROOT ULTRAVIOLET B-SENSITIVE1/WEAK AUXIN RESPONSE3 Is Essential for Polar Auxin Transport in Arabidopsis
    PLANT PHYSIOLOGY, 2013; 162(2):965-976
  36. The Caspase-Related Protease Separase (EXTRA SPINDLE POLES) Regulates Cell Polarity and Cytokinesis in Arabidopsis
    Plant Cell 2013; 25(6):2171-2186
  37. Cell Polarity and Patterning by PIN Trafficking through Early Endosomal Compartments in Arabidopsis thaliana
    PLOS genetics May 30 2013
  38. Auxin: simply complicated
    Journal of Experimental Botany, Online: May 13, 2013
  39. ROOT UVB SENSITIVE 1/WEAK AUXIN RESPONSE 3 Is Essential for Polar Auxin Transport in Arabidopsis
    Plant Physiology April 2013 Published online before print April 2013
  40. Baster P, Robert S, Kleine-Vehn J, Vanneste S, Kania U, Grunewald W, De Rybel B, Beeckman T, Friml J
    SCF(TIR1/AFB)-auxin signalling regulates PIN vacuolar trafficking and auxin fluxes during root gravitropism
    EMBO J. 2012 Dec 4
  41. Chen X, Naramoto S, Robert S, Tejos R, Löfke C, Lin D, Yang Z, Friml J
    ABP1 and ROP6 GTPase Signaling Regulate Clathrin-Mediated Endocytosis in Arabidopsis Roots
    Curr Biol. 2012, 22(14):1326-32
  42. Recycling, clustering, and endocytosis jointly maintain PIN auxin carrier polarity at the plasma membrane
    Molecular Systems Biology 7:540
  43. Clusters of bioactive compounds target dynamic endomembrane networks in vivo
    PNAS 2011, 108(43):17850-17855
  44. Barberon M, Zelazny E, Robert S, Conéjéro G, Curie C, Friml J, Vert G
    Monoubiquitin-dependent endocytosis of the IRON-REGULATED TRANSPORTER 1 (IRT1) transporter controls iron uptake in plants
    Proceedings of the National Academy of Sciences of the United State of America: 2011 108:E450-E458
  45. Kitakura S. Vanneste S, Robert S, Löfke C, Teichmann T, Tanaka H, Friml J
    Clathrin mediates endocytosis and polar distribution of PIN auxin transporters in Arabidopsis
    The Plant Cell: 2011, 23:1920-1931
  46. Arabidopsis ROOT UVB SENSITIVE2/WEAK AUXIN RESPONSE1 is required for polar auxin transport
    The Plant Cell: 2010 22:1749-1761
  47. ABP1 mediates auxin inhibition of clathrin-dependent endocytosis in Arabidopsis
    Cell: 2010 143:111-121
  48. Robert S, Raikhel NV, Hicks GR
    Powerful partners: Arabidopsisi and chemical genomics
    In: The Arabidopsis Book. Rockville, MD: American Society of Plant Biologists; 2009. p 1-16.
  49. Drakakaki G, Robert S., Raikhel NV, Hicks GR
    Chemical dissection of endosomal pathways
    Plant Signaling and Behavior: 2009 4:1-6
  50. Naramoto S, Kleine-Vehn J, Robert S, Fujimoto M, Dainobu T, Paciorek T, Ueda T, Nakano A, Van Montagu MCE, Fukuda H, Friml J
    ADP-ribosylation factor machinery mediates endocytosis in plant cells
    Proceedings of the National Academy of Sciences of the United States of America: 2010 107:21890-21895
  51. Robert S, Chary N, Drakakaki G, Yang Z, Raikhel N, Hicks G
    Endosidin1 defines a compartment involved in endocytosis of the brassinosteroid receptor BRI1 and the auxin transporters PIN2 and AUX1
    Proceedings of the National Academy of Sciences of the United States of America: 2008 105:8464-8469
  52. Isolation of intact vacuoles from Arabidopsis rosette leaf-derived protoplasts
    Nature Protocols: 2007 2:259-262
  53. Divergent functions of VTI12 and VTI11 in trafficking to storage and lytic vacuoles in Arabidopsis
    Proceedings of the National Academy of Sciences of the United States of America: 2007 104:3645-3650
  54. Drakakaki G, Zabotina O, Delgado I, Robert S, Keegstra K, Raikhel N
    Arabidopsis RGP1 and RGP2 are essential for pollen development
    Plant Physiology: 2006 142:1480-1492
  55. Robert S, Bichet A, Grandjean O, Kierskowski D, Satiat-Jeunmaitre B, Pelletier S, Hauser M-T, Höfte H, Vernhettes S
    An Arabidopsis endo-1,4-β-D-glucanase involved in cellulose synthesis undergoes regulated cellular cycling
    The Plant Cell: 2005 17:3378-3389
  56. Robert S, Mouille G, Höfte H
    The mechanism and regulation of cellulose synthesis in primary wall: lessons from primary cell wall mutants
    Cellulose: 2004 11:351-364