Journal of Biological Chemistry
Volume 277, Issue 47, 22 November 2002, Pages 45338-45346
Journal home page for Journal of Biological Chemistry

MEMBRANE TRANSPORT STRUCTURE FUNCTION AND BIOGENESIS
High Affinity Amino Acid Transporters Specifically Expressed in Xylem Parenchyma and Developing Seeds of Arabidopsis *

https://doi.org/10.1074/jbc.M207730200Get rights and content
Under a Creative Commons license
open access

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 fromArabidopsis. Histochemical promoter-β-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.

Cited by (0)

*

This work was supported by the DFG Projects Aminosäuretransport and Schwerpunkt Membrantransport SPP1108 (FR989/10–1).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

§

Both authors contributed equally to this work.

Present address: XenoPort, Inc. 2631 Hanover St., Palo Alto, CA 94304.

Supported by National Science Foundation Grant IBN-0135344 and the United States Department of Agriculture Grant NRICGP 2001-35318-10990.