Amino Acid Transport into Cultured Tobacco Cells

Harrington, Helen; Henke, Randolph R.

doi:10.1104/pp.67.2.373

Cited by 34 publications

(20 citation statements)

References 13 publications

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“…In a few cases, there is evidence for two carriers with an apparently broad specificity, one having a high affinity but a relatively low capacity, the other having a low affinity but a high capacity (4,10). In addition to unspecific amino acid carriers, many plant tissues seem to have an apparently specific carrier for basic amino acids (1,5,9,12,14). However, the number ofamino acid carriers cannot be taken as established in any higher plant tissue.…”

Section: Discussionmentioning

confidence: 99%

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Uptake of Glutamine by the Scutellum of Germinating Barley Grain

Väisänen¹,

Sopanen²

1985

Plant Physiol.

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Scutella separated from germinating grains of barley (Hordeum vulgare L. cv Himalaya) took up '4Cqglutamine at an initial rate of about 10 micromoles-gram-'.hour-' in the standard assay conditions (pH 5, 30°C, 1 millimolar glutamine). Inhibition by unlabeled glutamine and by dinitrophenol indicated that about 95% of the uptake was due to carriermediated active transport. The pH optimum of the uptake was 5, and after correction for a nonmediated component the uptake appeared to conform to Michaelis-Menten kinetics with an apparent K. of about 2 millimolar and a V.. of about 25 micromoles -gram-'. hour-'.The uptake of glutamine was inhibited by all of the 18 amino acids tested; the mode of inhibition was studied only with proline and was competitive. Eight of the ten amino acids tested at high concentrations appeared to be able to inhibit the mediated uptake of glutamine virtually completely. However, when the inhibitory effect of asparagine was extrapolated to an infinitely high concentration of asparagine, about 24% of the mediated uptake of glutamine remained uninhibited. These results suggest that glutamine is taken up by two (or more) rather unspecific amino acid uptake systems, the minor one having no affinity for asparagine.Glutamine and alanine could completely inhibit the mediated uptake of I millimolar leucine, but about 12% of the mediated uptake appeared to be uninhibitable by asparagine. Furthermore, the ratio of the mediated uptake of glutamine to that of leucine changed from 0.9 to 1.7 between days I and 3 of germination. These results give further support for the presence of two unspecific amino acid uptake systems in barley scutella.During germination of a barley grain the reserve proteins in the starchy endosperm are hydrolyzed into a mixture of short oligopeptides and free amino acids (16,17). These are taken up into the scutellum, most probably into the epithelial cells (11,26, and references cited therein), from where the amino acids taken up or liberated from the peptides are transferred to the growing seedling.Previously, some properties of the uptake of amino acids into the scutellum were studied using leucine as substrate (18,26). The uptake of leucine is separate from the uptake of peptides and is due to active transport. The pH optimum is near 5, the pH ofthe starchy endosperm. The rate ofuptake increases rapidly in the beginning of germination and attains a high level in comparison to the rates of uptake in other parts of the seedling. Glutamine has earlier been shown to be rapidly taken up into slices of corn scutella, the uptake being carrier-mediated active transport (28). Here, we report some general properties of the uptake of glutamine into whole barley scutella. Using kinetic analysis of the inhibitory effects of other amino acids, we have also attempted to find out whether glutamine is taken up by one or more uptake systems.Some preliminary results have already been reported (23, 27 Uptake Assay. The standard procedure was modified from the leucine uptake assay used earl...

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Section: Discussionmentioning

confidence: 99%

“…2, 3,6,7,9,10,13,20). In a few cases, there is evidence for two carriers with an apparently broad specificity, one having a high affinity but a relatively low capacity, the other having a low affinity but a high capacity (4,10).…”

Section: Discussionmentioning

confidence: 99%

Uptake of Glutamine by the Scutellum of Germinating Barley Grain

Väisänen¹,

Sopanen²

1985

Plant Physiol.

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“…Despite their importance-e.g., for the nutritional quality of seeds-synthesis and accumulation of lysine in seeds and import are poorly understood. Biochemical and genetic studies have provided evidence for carrier proteins mediating basic amino acid transport (32)(33)(34)(35)(36)(37). Complementation of a histidine uptake deficiency of yeast enabled the isolation and characterization of AAT1 that is homologous to amino acid transporters from bacterial, fungal, and mammalian but not plant origin.…”

Section: Discussionmentioning

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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“…Half of the protoplasts from a given isolation were preincubated in PIM and the other half in PIM pli4s 10 Am CCCP for 20 min in the dark. Suspensions were then centrifuged at lOOg for 7 min and resuspended in PIM and PIM plus 10 /LM CCCP, respectively.…”

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confidence: 99%

Transport of the Herbicide 3-Amino-1,2,4-Triazole by Cultured Tobacco Cells and Leaf Protoplasts

Singer

McDaniel²

1982

Plant Physiol.

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Transport of the herbicide amitrole (3-amiao-1,2,4-triazole) by suspension cultured cells and leaf protoplasts of Nicotiana tahacum cv. Wisconsin 38 has been investigated. Cells were batch-cultured and routinely assayed 3 days after subculturing. Uptake rate was pH-independent, energy independent, and culture growth phase-dependent, with growing cells exhibiting the highest rates. At a concentration of 0.2 miimolar amitrole, uptake rates yielded a Qlio of 1.6 in the 18 to 28°C temperature range. Amitrole was not concentrated over a 48-hour period and showed unsaturable kinetics over the concentration range of 0.01 to 50.0 millimolar. Uptake was not significantly influenced by a 100-fold higher concentration of several amino acids (L-Asp, y-amino-n-butyric acid, L-His, L-Leu, L-Met, L-Trp), sucrose, glucose, fructose, and oxaloacetic acid. Uptake rate inhibition by malic acid and stimulation by NH4SCN were statistically significant. Amitrole was bound to cellular material, but uptake of amitrole by tobacco leaf protoplasts demonstrated that cell walls did not qualitatively influence uptake. These results indicate that amitrole enters the cells via simple diffusion.The uptake of ions and organic molecules by whole plants, tissues and cultured cells has been investigated (22). However, herbicide uptake by plants cells has received minimal attention and only a few herbicides have been studied in any detail (4,5,9,14,24). Although numerous amitrole2 translocation studies have been conducted (1), the mechanism of amitrole uptake into plant cells has not been reported. The herbicides glyphosate (N-phosphonomethylglycine) (9) and oryzalin (3,5-dinitro-N,N-dipropylsulfanilamide) (24) appear to be taken up into sugar beet leaf discs and corn root apices, respectively, by an energy independent mechanism. Although amitrole is structurally similar to histidine and might enter a cell via the histidine carrier system (18) bonyl cyanide m-chlorophenyl hydrazone; GABA, y-amino-n-butyric acid; PIM, protoplast incubation medium.MATERIALS AND METHODS Cell Culture and Assay. Cell culture and assay procedures have been described previously (2, 3). Cell suspensions of Nicotiana tabacum cv. Wisconsin 38 were maintained in 125 ml Erlenmeyer flasks containing 50 ml of L and S medium. Cells were subcultured every 7 days by adding 50 ml L and S medium to a 125 ml Erlenmeyer flask containing a 50 ml suspension of stationary phase cells and dividing the resulting suspension between two 125 ml flasks. The subculture inoculum size was about 9 g fresh weight and 4 d after subculturing, the cells had completed their period of rapid growth. Uptake rate was measured in growing cells where HV is the volume of cell debris resulting from the homogenization of the cells in a sample. HV has been related to other standardization parameters (2, 17). The incubation medium was not buffered. The initial pH was about 5.5 and during a 9 min assay the pH did not change. Except where noted, data points are the means of three determinations ± SE.Metaboli...

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Amino Acid Transport into Cultured Tobacco Cells

Cited by 34 publications

References 13 publications

Uptake of Glutamine by the Scutellum of Germinating Barley Grain

Uptake of Glutamine by the Scutellum of Germinating Barley Grain

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

Transport of the Herbicide 3-Amino-1,2,4-Triazole by Cultured Tobacco Cells and Leaf Protoplasts

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