Transporters for nitrogenous compounds in plants

Frommer, Wolf B.; Kwart, Marion; Hirner, Brigitte; Fischer, W; Hummel, Sabine; Ninnemann, Olaf

doi:10.1007/bf00016495

Cited by 56 publications

(19 citation statements)

References 149 publications

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“…Transport is complex since a mixture of amino acids A B is translocated (1,29,30). Major components of xylem and phloem are acidic amino acids and amides.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Seed and vascular expression of a high-affinity transporter for cationic amino acids in Arabidopsis.

Frommer

Hummel

Unseld

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

101

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“…Transport is complex since a mixture of amino acids A B is translocated (1,29,30). Major components of xylem and phloem are acidic amino acids and amides.…”

Section: Discussionmentioning

confidence: 99%

“…The complexity of plant amino acid translocation in time and space made this assumption questionable. Amino acids are distributed through xylem and phloem to supply importing organs-i.e., seeds (1). Transport measurements in several plant species provided evidence for low-and high-affinity transport systems.…”

mentioning

confidence: 99%

Seed and vascular expression of a high-affinity transporter for cationic amino acids in Arabidopsis.

Frommer

Hummel

Unseld

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

101

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“…2 Throughout the experiment, substrate-induced currents were recorded using Fetchex software (Axon Instruments, Inc., Foster City, CA). Oocytes were clamped at potentials ranging from Ϫ10 to Ϫ90 mV and superfused with transport buffer at a rate of 160 l/min.…”

Section: Methodsmentioning

confidence: 99%

“…[1][2][3][4]. Kinetic analysis of amino acid uptake into plasma membrane vesicles isolated from sugar beet leaves suggests the presence of four H ϩ -coupled amino acid transport systems (5-7), and at least 10 H ϩ /amino acid transporters have been isolated by complementing yeast amino acid transport mutants with plant cDNA libraries (8 -12).…”

mentioning

confidence: 99%

Specificity and Stoichiometry of the ArabidopsisH+/Amino Acid Transporter AAP5

Boorer

Fischer

1997

Journal of Biological Chemistry

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The H؉ -dependent AAP5 amino acid transporter from Arabidopsis thaliana was expressed in Xenopus oocytes, and we used radiotracer flux and electrophysiology methods to investigate its substrate specificity and stoichiometry. Inward currents of up to 9 A were induced by a broad spectrum of amino acids, including anionic, cationic, and neutral amino acids. The apparent affinity of AAP5 for amino acids was influenced by the position of side chain branches, bulky ring structures, and charged groups. The maximal current was dependent on amino acid charge, but was relatively independent of amino acid structure. A detailed kinetic analysis of AAP5 using lysine, alanine, glutamate, and histidine revealed H ؉ -dependent differences in the apparent affinity constants for each substrate. The differences were correlated to the effect of H ؉ concentration on the net charge of each amino acid and suggested that AAP5 transports only the neutral species of histidine and glutamate. Stoichiometry experiments, whereby the uptake of 3 H-labeled amino acid and net inward charge were simultaneously measured in voltage-clamped oocytes, showed that the charge:amino acid stoichiometry was 2:1 for lysine and 1:1 for alanine, glutamate, and histidine. The results confirm that histidine is transported in its neutral form and show that the positive charge on lysine contributes to the magnitude of its inward current. Thus, the transport stoichiometry of AAP5 is 1 H ؉ :1 amino acid irrespective of the net charge on the transported substrate. Structural features of amino acid molecules that are involved in substrate recognition by AAP5 are discussed.Transport of amino acids across the plasma membrane of higher plants is mediated by proton-coupled transport proteins that utilize the electrochemical gradient for H ϩ to drive the uphill transport of amino acids (reviewed in Refs. 1-4). Kinetic analysis of amino acid uptake into plasma membrane vesicles isolated from sugar beet leaves suggests the presence of four H ϩ -coupled amino acid transport systems (5-7), and at least 10 H ϩ /amino acid transporters have been isolated by complementing yeast amino acid transport mutants with plant cDNA libraries (8 -12). These transporters have very broad and overlapping specificities. However, each exhibits a preference for amino acids possessing a particular molecular geometry or charge. Analysis of the substrate specificity of amino acid transporters in yeast cells and plasma membrane vesicles is traditionally accomplished by measuring the inhibition of amino acid transport activity by various substrates. Competition experiments yield information on substrates that interact with amino acid transporters, but do not allow a distinction between substrates that are transported and those that act as inhibitors.We previously analyzed the specificity and kinetic properties of the Arabidopsis AAP1 H ϩ /amino acid transporter by expressing the cloned gene in Xenopus oocytes and measuring substrate-induced currents using electrophysiology methods (13). AAP1 transpo...

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“…Three gene families encoding plant amino acid transporters were identified by complementation of yeast mutants defective in the uptake of proline, citrulline, or histidine (Frommer et al, 1994b). The increasing number of genes encoding plant amino acid permeases indicates that amino acid transport in plants might be as complex as transport in yeast (Grenson, 1992;Nelissen et al, 1995).…”

Section: Identification Of Plant Amino Acid Transporters Independent mentioning

confidence: 99%

Salt stress-induced proline transporters and salt stress-repressed broad specificity amino acid permeases identified by suppression of a yeast amino acid permease-targeting mutant.

et al. 1996

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A yeast mutant lacking SHRS, a protein specifically required for correct targeting of plasma membrane amino acid permeases, was used to study the targeting of plant transportem and as a tool to isolate new SHR3-independent amino acid transportem. For this purpose, an shr3 mutant was transformed with an Arabidopsis cDNA library. Thirty-four clones were capable of growth under selective conditions, but none showed homology with SHR3. However, genes encoding eight different amino acid transportem belonging to three different transporter families were isolated. Five of these are members of the general amino acid permease (AAP) gene family, one is a member of the NTR family, encoding an oligopeptide transporter, and two belong to a new class of transporter genes. A functional analysis of the latter two genes revealed that they encode specific proline transporters (ProT) that are distantly related to the AAP gene family. PfoTT was found to be expressed in all organs, but highest levels were found in roots, stems, and flowers. Expression in flowers was highest in the floral stalk phloem that enters the carpels and was downregulated after fertilization, indicating a specific role in supplying the ovules with proline. ProT2 transcripts were found ubiquitously throughout the plant, but expression was strongly induced under water or salt stress, implying that ProT2 plays an important role in nitrogen distribution during water stress, unlike members of the AAPgene family whose expression was repressed under the same conditions. These results corroborate the general finding that under water stress, amino acid export is impaired whereas proline export is increased.

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Transporters for nitrogenous compounds in plants

Cited by 56 publications

References 149 publications

Seed and vascular expression of a high-affinity transporter for cationic amino acids in Arabidopsis.

Seed and vascular expression of a high-affinity transporter for cationic amino acids in Arabidopsis.

Specificity and Stoichiometry of the ArabidopsisH+/Amino Acid Transporter AAP5

Salt stress-induced proline transporters and salt stress-repressed broad specificity amino acid permeases identified by suppression of a yeast amino acid permease-targeting mutant.

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