A fast brassinolide-regulated response pathway in the plasma membrane of Arabidopsis thaliana.
To understand molecular processes in living plant cells, quantitative spectro-microscopic technologies are required. By combining fluorescence lifetime spectroscopy with confocal microscopy, we studied the subcellular properties and function of a GFP-tagged variant of the plasma membrane-bound brassinosteroid receptor BRI1 (BRI1-GFP) in living cells of Arabidopsis seedlings. Shortly after adding brassinolide, we observed BRI1-dependent cell-wall expansion, preceding cell elongation. In parallel, the fluorescence lifetime of BRI1-GFP decreased, indicating an alteration in the receptor's physico-chemical environment. The parameter modulating the fluorescence lifetime of BRI1-GFP was found to be BL-induced hyperpolarization of the plasma membrane. Furthermore, for induction of hyperpolarization and cell-wall expansion, activation of the plasma membrane P-ATPase was necessary. This activation required BRI1 kinase activity, and was mediated by BL-modulated interaction of BRI1 with the P-ATPase. Our results were used to develop a model suggesting that there is a fast BL-regulated signal response pathway within the plasma membrane that links BRI1 with P-ATPase for the regulation of cell-wall expansion.
Center for Plant Molecular Biology, Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany.
Katharina
K
Caesar
Kirstin
K
Elgass
Zhonghua
Z
Chen
Peter
P
Huppenberger
Janika
J
Witthöft
Frank
F
Schleifenbaum
Michael R
MR
Blatt
Claudia
C
Oecking
Klaus
K
Harter
D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D000251:Adenosine Triphosphatases; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D060406:Brassinosteroids; D002462:Cell Membrane / Q000201:enzymology / Q000502:physiology*; D002473:Cell Wall / Q000187:drug effects / Q000502:physiology*; D002777:Cholestanols / Q000494:pharmacology*; D004594:Electrophysiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008564:Membrane Potentials; D010766:Phosphorylation; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D019346:Sodium Acetate / Q000494:pharmacology; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000502:physiology
D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D002777:Cholestanols; D011993:Recombinant Fusion Proteins; D013260:Steroids, Heterocyclic; D049452:Green Fluorescent Proteins; D015084:2,4-Dichlorophenoxyacetic Acid; D019346:Sodium Acetate; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis; D000251:Adenosine Triphosphatases; C023623:brassinolide