Characterization of the putative amino acid transporter genes AtCAT2, 3 &4: the tonoplast localized AtCAT2 regulates soluble leaf amino acids.
The plant vacuole constitutes a large transient storage compartment for nutrients, proteins and metabolites, and is a major cellular sink for toxic waste compounds. Amino acids can cross the vacuolar membrane via specific transport proteins, which are molecularly not well characterized. Two members of a small subfamily of the cationic amino acid transporters, AtCAT2 and AtCAT4, were primarily localized at the tonoplast when tagged with GFP. The closely related AtCAT3, by contrast, was detected in the endoplasmic reticulum membrane. The exchange of a di-acidic motif at the carboxy-tail affected their sub-cellular localization, with larger effects visible in transiently transformed protoplasts compared to stably expressing plant lines. The genes have broad, partially overlapping tissue expression, with CAT2 dominating in most tissues. Loss-of-function mutants of individual CATs showed no visible phenotype under various conditions, but the overall tissue concentration of amino acids was increased in soil-grown cat2 mutants. The data suggest that CAT2 is a critical target of leaf amino acid concentrations and manipulation of this tonoplast transporter can significantly alter total tissue amino acid concentrations.
Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593 Stuttgart, Germany; Center for Molecular Biology of Plants (ZMBP), Microscopy Unit, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany.
Huaiyu
H
Yang
Center for Molecular Biology of Plants (ZMBP), Microscopy Unit, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany.
Melanie
M
Krebs
Center for Molecular Biology of Plants (ZMBP), Microscopy Unit, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany.
York-Dieter
YD
Stierhof
Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593 Stuttgart, Germany; Center for Molecular Biology of Plants (ZMBP), Microscopy Unit, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany. Electronic address: u.ludewig@uni-hohenheim.de.
Uwe
U
Ludewig
D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism; D026923:Amino Acid Transport Systems, Basic / Q000235:genetics* / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D049408:Luminescent Agents / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
D026905:Amino Acid Transport Systems; D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D029681:Arabidopsis Proteins; D049408:Luminescent Agents; C000593856:cationic amino acid transporter 2, Arabidopsis; C000593857:cationic amino acid transporter 3, Arabidopsis; C000593858:cationic amino acid transporter 4, Arabidopsis; D049452:Green Fluorescent Proteins
Arabidopsis; Cationic amino acid transporter; Nitrogen; Tonoplast; Vacuole