Journal Article

Visualization of BRI1 and SERK3/BAK1 Nanoclusters in Arabidopsis Roots

van Esse, Wilma, Hamers, Danny S., Hohlbein, Johannes, Nolles, Antsje, Aan den Toorn, Marije, Bücherl, Christoph A., de Vries, Sacco C., Borst, Jan Willem, Hutten, Stefan J.

2017

Overview

Brassinosteroids (BRs) are plant hormones that are perceived at the plasma membrane (PM) by the ligand binding receptor BRASSINOSTEROID-INSENSITIVE1 (BRI1) and the co-receptor SOMATIC EMBRYOGENESIS RECEPTOR LIKE KINASE 3/BRI1 ASSOCIATED KINASE 1 (SERK3/BAK1). To visualize BRI1-GFP and SERK3/BAK1-mCherry in the plane of the PM, variable-angle epifluorescence microscopy (VAEM) was employed, which allows selective illumination of a thin surface layer. VAEM revealed an inhomogeneous distribution of BRI1-GFP and SERK3/BAK1-mCherry at the PM, which we attribute to the presence of distinct nanoclusters. Neither the BRI1 nor the SERK3/BAK1 nanocluster density is affected by depletion of endogenous ligands or application of exogenous ligands. To reveal interacting populations of receptor complexes, we utilized selective-surface observation-fluorescence lifetime imaging microscopy (SSO-FLIM) for the detection of Förster resonance energy transfer (FRET). Using this approach, we observed hetero-oligomerisation of BRI1 and SERK3 in the nanoclusters, which did not change upon depletion of endogenous ligand or signal activation. Upon ligand application, however, the number of BRI1-SERK3 /BAK1 hetero-oligomers was reduced, possibly due to endocytosis of active signalling units of BRI1-SERK3/BAK1 residing in the PM. We propose that formation of nanoclusters in the plant PM is subjected to biophysical restraints, while the stoichiometry of receptors inside these nanoclusters is variable and important for signal transduction.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Arabidopsis / Arabidopsis - metabolism / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Biochemie / Biochemistry / Biofysica / Biology and Life Sciences / Biophysics / BIOS Plant Development Systems / Brassinosteroids / Cell cycle / Cell division / Cellular signal transduction / Depletion / Embryogenesis / Embryonic growth stage / Endocytosis / Energy consumption / Energy transfer / Engineering and Technology / EPS / Fluorescence / Fluorescence Resonance Energy Transfer / Hormones / Kinases / Laboratories / Laboratorium voor Biofysica / Laboratorium voor Moleculaire biologie / Laboratory of Molecular Biology / Ligands / Lipids / Luminance distribution / Microscopy / Nanoclusters / Nanostructures / Oligomers / Phosphorylation / Physical Chemistry and Soft Matter / Physical Sciences / Physiological aspects / Plant hormones / Plant Roots - metabolism / PRI BIOS Plant Development Systems / Protein Kinases - metabolism / Protein-Serine-Threonine Kinases - metabolism / Proteins / Receptors / Recovery (Medical) / Research and Analysis Methods / Research parks / Signal transduction / Signaling / Somatic embryogenesis / Stoichiometry / Surface boundary layer / Transduction / VLAG