title: Insights into the localization and function of the membrane trafficking regulator GNOM ARF-GEF at the Golgi apparatus in Arabidopsis.
abstract: GNOM is one of the most characterized membrane trafficking regulators in plants, with crucial roles in development. GNOM encodes an ARF-guanine nucleotide exchange factor (ARF-GEF) that activates small GTPases of the ARF (ADP ribosylation factor) class to mediate vesicle budding at endomembranes. The crucial role of GNOM in recycling of PIN auxin transporters and other proteins to the plasma membrane was identified in studies using the ARF-GEF inhibitor brefeldin A (BFA). GNOM, the most prominent regulator of recycling in plants, has been proposed to act and localize at so far elusive recycling endosomes. Here, we report the GNOM localization in context of its cellular function in Arabidopsis thaliana. State-of-the-art imaging, pharmacological interference, and ultrastructure analysis show that GNOM predominantly localizes to Golgi apparatus. Super-resolution confocal live imaging microscopy identified GNOM and its closest homolog GNOM-like 1 at distinct subdomains on Golgi cisternae. Short-term BFA treatment stabilizes GNOM at the Golgi apparatus, whereas prolonged exposures results in GNOM translocation to trans-Golgi network (TGN)/early endosomes (EEs). Malformed TGN/EE in gnom mutants suggests a role for GNOM in maintaining TGN/EE function. Our results redefine the subcellular action of GNOM and reevaluate the identity and function of recycling endosomes in plants.
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Molecular Membrane Biology laboratory, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan Department of Life Science, International Christian University, Mitaka-shi, Tokyo 181-8585, Japan naramoto@bs.s.u-tokyo.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Naramoto
authors.affiliation: Department of Botany and Genetics, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: Marisa S
authors.initials: MS
authors.lastname: Otegui
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Natsumaro
authors.initials: N
authors.lastname: Kutsuna
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Riet
authors.initials: R
authors.lastname: de Rycke
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Dainobu
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Michael
authors.initials: M
authors.lastname: Karampelias
authors.affiliation: Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Fujimoto
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Elena
authors.initials: E
authors.lastname: Feraru
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Miki
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Fukuda
authors.affiliation: Molecular Membrane Biology laboratory, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan Live Cell Molecular Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria.
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D017930:Genes, Reporter; D006056:Golgi Apparatus / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C088087:GNOM protein, Arabidopsis; D020662:Guanine Nucleotide Exchange Factors; D011993:Recombinant Fusion Proteins; D020126:Brefeldin A; D020727:ADP-Ribosylation Factors