Overexpression of GLUTAMINE DUMPER1 leads to hypersecretion of glutamine from Hydathodes of Arabidopsis leaves.
Secretion is a fundamental process providing plants with the means for disposal of solutes, improvement of nutrient acquisition, and attraction of other organisms. Specific secretory organs, such as nectaries, hydathodes, and trichomes, use a combination of secretory and retrieval mechanisms, which are poorly understood at present. To study the mechanisms involved, an Arabidopsis thaliana activation tagged mutant, glutamine dumper1 (gdu1), was identified that accumulates salt crystals at the hydathodes. Chemical analysis demonstrated that, in contrast with the amino acid mixture normally present in guttation droplets, the crystals mainly contain Gln. GDU1 was cloned and found to encode a novel 17-kD protein containing a single putative transmembrane span. GDU1 is expressed in the vascular tissues and in hydathodes. Gln content is specifically increased in xylem sap and leaf apoplasm, whereas the content of several amino acids is increased in leaves and phloem sap. Selective secretion of Gln by the leaves may be explained by an enhanced release of this amino acid from cells. GDU1 study may help to shed light on the secretory mechanisms for amino acids in plants.
Pilot
Guillaume
G
Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, D-72076 Germany.
Stransky
Harald
H
Bushey
Dean F
DF
Pratelli
Réjane
R
Ludewig
Uwe
U
Wingate
Vincent P M
VP
Frommer
Wolf B
WB
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008565:Membrane Proteins / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism
D000596:Amino Acids; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C492757:GDU1 protein, Arabidopsis; D008565:Membrane Proteins; C036483:T-DNA