title: A member of the mitogen-activated protein 3-kinase family is involved in the regulation of plant vacuolar glucose uptake.
abstract: Vacuolar solute accumulation is an important process during plant development, growth and stress responses. Although several vacuolar carriers have been identified recently, knowledge regarding the regulation of transport is still limited. Solute accumulation may be controlled by various factors, such as alterations in carrier abundance or activity. Phosphorylation via kinases is a well-known principle for activation or deactivation of proteins. Several phosphorylated proteins have been identified in the tonoplast proteome; however, kinases that catalyse the phosphorylation of tonoplast proteins are currently unknown. The tonoplast monosaccaride transporter from Arabidopsis (AtTMT1) and its homologue from barley have multiple phosphorylation sites in their extremely large loops. Here we demonstrate that the loop of AtTMT1 interacts with a mitogen-activated triple kinase-like protein kinase (VIK), that an aspartate-rich loop domain is required for effective interaction, and that the presence of VIK stimulates glucose import into isolated vacuoles. Furthermore, the phenotype of VIK loss-of-function plants strikingly resembles that of plants lacking AtTMT1/2. These data suggest that VIK-mediated phosphorylation of the AtTMT1 loop enhances carrier activity and consequently vacuolar sugar accumulation. As many phosphorylated proteins have been identified in the tonoplast, differential phosphorylation may be a general mechanism regulating vacuolar solute import.
authors.affiliation: Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger Straße, D-67653 Kaiserslautern, Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Wingenter
authors.forename: Oliver
authors.initials: O
authors.lastname: Trentmann
authors.forename: Irina
authors.initials: I
authors.lastname: Winschuh
authors.forename: Imke I
authors.initials: II
authors.lastname: Hörmiller
authors.forename: Arnd G
authors.initials: AG
authors.lastname: Heyer
authors.forename: Jörg
authors.initials: J
authors.lastname: Reinders
authors.forename: Alexander
authors.initials: A
authors.lastname: Schulz
authors.forename: Dietmar
authors.initials: D
authors.lastname: Geiger
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D019069:Cell Respiration; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D058503:Mesophyll Cells / Q000378:metabolism; D008856:Microscopy, Fluorescence / Q000379:methods; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D059828:Plant Cells / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D058849:Protein Refolding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D009004:Monosaccharide Transport Proteins; D011994:Recombinant Proteins; C518496:Tmt1 protein, Arabidopsis; D001224:Aspartic Acid; D020930:MAP Kinase Kinase Kinases; D005947:Glucose