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PMID:12244056

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Citation

Okumoto, S, Schmidt, R, Tegeder, M, Fischer, WN, Rentsch, D, Frommer, WB and Koch, W (2002) High affinity amino acid transporters specifically expressed in xylem parenchyma and developing seeds of Arabidopsis. J. Biol. Chem. 277:45338-46

Abstract

Arabidopsis amino acid transporters (AAPs) show individual temporal and spatial expression patterns. A new amino acid transporter, AAP8 was isolated by reverse transcription-PCR. Growth and transport assays in comparison to AAP1-5 characterize AAP8 and AAP6 as high affinity amino acid transport systems from Arabidopsis. Histochemical promoter-beta-glucuronidase (GUS) studies identified AAP6 expression in xylem parenchyma, cells requiring high affinity transport due to the low amino acid concentration in xylem sap. AAP6 may thus function in uptake of amino acids from xylem. Histochemical analysis of AAP8 revealed stage-dependent expression in siliques and developing seeds. Thus AAP8 is probably responsible for import of organic nitrogen into developing seeds. The only missing transporter of the family AAP7 was nonfunctional in yeast with respect to amino acid transport, and expression was not detectable. Therefore, AAP6 and -8 are the only members of the family able to transport aspartate with physiologically relevant affinity. AAP1, -6 and -8 are the closest AAP paralogs. Although AAP1 and AAP8 originate from a duplicated region on chromosome I, biochemical properties and expression pattern diverged. Overlapping substrate specificities paired with individual properties and expression patterns point to specific functions of each of the AAP genes in nitrogen distribution rather than to mere redundancy.

Links

PubMed Online version:10.1074/jbc.M207730200

Keywords

Amino Acid Transport Systems/classification; Amino Acid Transport Systems/genetics; Amino Acid Transport Systems/metabolism; Arabidopsis/anatomy & histology; Arabidopsis/genetics; Arabidopsis/physiology; Arabidopsis Proteins/classification; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Cloning, Molecular; Exons/genetics; Glucuronidase/genetics; Glucuronidase/metabolism; Introns/genetics; Plant Structures/metabolism; Promoter Regions, Genetic; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Seeds/metabolism; Tobacco/anatomy & histology; Tobacco/genetics; Tobacco/metabolism; Yeasts/genetics; Yeasts/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:AAP8

located_in

GO:0016020: membrane

ECO:0000250: sequence similarity evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:AAP7

located_in

GO:0016020: membrane

ECO:0000250: sequence similarity evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:AAP7

acts_upstream_of_or_within

GO:0006865: amino acid transport

ECO:0000250: sequence similarity evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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