Nitrite Transport in Chloroplast Inner Envelope Vesicles (I. Direct Measurement of Proton-Linked Transport)

Shingles, Richard; Roh, Michael H.; McCarty, Richard E.

doi:10.1104/pp.112.3.1375

Cited by 62 publications

(47 citation statements)

References 24 publications

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“…NO 2 Ϫ transport from the cytosol into the chloroplast involves the diffusion of HNO 2 across chloroplast membranes and, therefore, requires the stroma to be more alkaline than the cytosol (36). Carbon dioxide at elevated concentrations can dissipate this pH gradient because additional CO 2 movement into the chloroplast acidifies the stroma (37) and because enhanced carbon fixation hydrolyzes ATP faster and requires supplementary proton exchange across the thylakoid membrane to regenerate this ATP.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen assimilation and growth of wheat under elevated carbon dioxide

Bloom

Smart

Nguyen

et al. 2002

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

193

173

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A tmospheric CO 2 concentrations have increased from about 280 to 370 mol mol Ϫ1 since 1800 (1, 2) and may reach 500-900 mol mol Ϫ1 by the end of the century (3). Several responses of higher plants to such changes were not anticipated (4). For example, a doubling of CO 2 level initially accelerates carbon fixation in C 3 plants by about 30%, yet after days to weeks of exposure to high CO 2 concentrations, depending on species, carbon fixation declines until it stabilizes at a rate that averages 12% above ambient controls (5). This general phenomenon, known as CO 2 acclimation, is correlated with a decline in the activity of Rubisco and other enzymes in the Calvin cycle (6, 7). The change in Calvin cycle enzyme activities is not necessarily selective; rather, it often follows a decline in overall shoot protein and N contents (8). Shoot N contents diminish by an average of 14% with a doubling of CO 2 (9), a difference that exceeds what would be expected if a given amount of N were diluted by additional biomass (8).In wheat, CO 2 acclimation varies with N supply (10, 11). Wheat shoots accumulate free NO 3 Ϫ under elevated CO 2 (12), and shoot protein declines (13) despite little change in total N (12, 14). Here, we present several lines of evidence that elevated CO 2 concentrations inhibit NO 3 Ϫ assimilation in wheat shoots and suggest two physiological mechanisms for this phenomenon. Materials and MethodsWe surface-sterilized wheat (Triticum aestivum cv. Veery 10) seeds for 1 min in 2.6% NaClO, washed them thoroughly with water, and germinated them for several days on thick paper toweling (germination paper) saturated with 1 mM CaSO 4 . Twenty seedlings were transplanted to 19-liter opaque plastic containers filled with an aerated nutrient solution containing 0.2 mM NH 4 NO 3 , 1 mM CaSO 4 , 0.5 mM K 2 HPO 4 , 0.5 mM KH 2 PO 4 , 1 mM MgSO 4 , 0.2 g liter Ϫ1 Fe-NaEDTA, and micronutrients (15). The nutrient solution was replenished every 3 days.The containers were placed in a controlled environment chamber [Conviron (Winnipeg, MB, Canada) PGV-36] equipped with a nondispersive infrared CO 2 analyzer (Horiba, Kyoto, no. APBA-250E) and a Conviron process controller that added CO 2 to maintain the chamber concentration at 360 mol mol Ϫ1 for the photon flux density (PFD) response experiments (i.e., shoot photosynthesis as a function of photosynthetic PFD at plant height) and either 360 or 700 mol mol Ϫ1 for the A-C i response (i.e., shoot photosynthesis as a function of internal CO 2 concentration) experiments. The growth͞N relations experiments were also conducted at 360 or 700 mol CO 2 mol Ϫ1 . The CO 2 added was filtered through a KMnO 4 column to remove contaminating hydrocarbons such as ethylene. A combination of high-pressure sodium, metal halide, and incandescent lamps provided a photosynthetic PFD of 700 mol m Ϫ2 s Ϫ1 at plant height. The light͞dark period was 16 h͞8 h at 25°C and 15°C, respectively.Gas-Exchange Measurements. We transferred a seedling about 14 days old into a measurement system in which a split ...

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Section: Resultsmentioning

confidence: 99%

Nitrogen assimilation and growth of wheat under elevated carbon dioxide

Bloom

Smart

Nguyen

et al. 2002

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

193

173

View full text Add to dashboard Cite

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“…(i) Transport of NO 2 Ϫ from the cytosol into the chloroplast involves the net diffusion of HNO 2 or cotransport of protons and NO 2 Ϫ across the chloroplast membrane. This requires the stroma to be more alkaline than the cytosol (44,45). Elevated concentrations of CO 2 can dissipate some of this pH gradient, because additional CO 2 movement into the chloroplast acidifies the stroma.…”

Section: Discussionmentioning

confidence: 99%

Nitrate assimilation in plant shoots depends on photorespiration

Rachmilevitch

Cousins

Bloom

2004

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

284

210

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Photorespiration, a process that diminishes net photosynthesis by Ϸ25% in most plants, has been viewed as the unfavorable consequence of plants having evolved when the atmosphere contained much higher levels of carbon dioxide than it does today. Here we used two independent methods to show that exposure of Arabidopsis and wheat shoots to conditions that inhibited photorespiration also strongly inhibited nitrate assimilation. Thus, nitrate assimilation in both dicotyledonous and monocotyledonous species depends on photorespiration. This previously undescribed role for photorespiration (i) explains several responses of plants to rising carbon dioxide concentrations, including the inability of many plants to sustain rapid growth under elevated levels of carbon dioxide; and (ii) raises concerns about genetic manipulations to diminish photorespiration in crops.global climate change ͉ CO2 acclimation ͉ Arabidopsis ͉ wheat R ubisco, the most prevalent protein in plants, indeed in the biosphere, catalyzes the reaction of ribulose-1,5-bisphosphate with either CO 2 or O 2 and thereby initiates, respectively, the CO 2 assimilatory (C 3 reductive) or photorespiratory (C 2 oxidative) pathways. The balance between the two reactions depends on the relative concentrations of CO 2 and O 2 at the site of catalysis. At current atmospheric levels of CO 2 (Ϸ360 mol⅐mol Ϫ1 ) and O 2 (Ϸ209,700 mol⅐mol Ϫ1 ), photorespiration in C 3 plants dissipates Ͼ25% of the carbon fixed during CO 2 assimilation (1). Thus, photorespiration has been viewed as a wasteful process, a vestige of the high CO 2 atmospheres under which plants evolved (2). At best, according to current thought, photorespiration may mitigate photoinhibition under high light and drought stress (2, 3) or may generate amino acids such as glycine for other metabolic pathways (4). Genetic modification of Rubisco to minimize photorespiration in crop plants has been the goal of many investigations (5).Atmospheric CO 2 concentrations will rise to somewhere between 600 and 1,000 mol⅐mol Ϫ1 by the end of the 21st century (6). Transferring C 3 plants from ambient (Ϸ360 mol⅐mol Ϫ1 ) to elevated (Ϸ720 mol⅐mol Ϫ1 ) CO 2 concentrations decreases photorespiration and initially stimulates net CO 2 assimilation and growth by Ϸ30% (7). With longer exposures to elevated CO 2 concentrations (days to weeks), however, net CO 2 assimilation and plant growth slow down until they stabilize at rates that average 12% (8) and 8% (9), respectively, above those of plants kept at ambient CO 2 concentrations. This phenomenon, known as CO 2 acclimation, is often associated with diminished activities of Rubisco and other enzymes in the C 3 reductive photosynthetic carbon cycle (10, 11), but the influence of elevated CO 2 may not be specific to these enzymes (12). Rather, CO 2 acclimation follows a 14% decline in overall shoot nitrogen concentrations (13), a change nearly double what would be expected if a given amount of nitrogen were diluted by the additional biomass that accumulates under elevated CO 2 conce...

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“…Whether nitrite enters into plant chloroplasts by a diffusion mechanism or by a mediated transport is an open question (Brunswick andCresswell, 1988a, 1988b;Shingles et al, 1996), and no nitrite transporter into the chloroplast has been studied at the molecular level until now. The existence of such nitrite transporters could be essential for controlling the amount of nitrite entering the chloroplast and avoiding intracellular accumulation of a toxic compound such as nitrite.…”

Section: Discussionmentioning

confidence: 99%

“…Some authors suggest that this is a regulated process mediated by a saturable nitrite transporter (Brunswick andCresswell 1988a, 1988b;Krämer et al, 1988), but others propose that there is no need for such a plastidic transporter because the nitrite could efficiently diffuse as nitrous acid (Shingles et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

The Chlamydomonas reinhardtii Nar1 Gene Encodes a Chloroplast Membrane Protein Involved in Nitrite Transport

2000

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A key step for nitrate assimilation in photosynthetic eukaryotes occurs within chloroplasts, where nitrite is reduced to ammonium, which is incorporated into carbon skeletons. The Nar1 gene from Chlamydomonas reinhardtii is clustered with five other genes for nitrate assimilation, all of them regulated by nitrate. Sequence analysis of genomic DNA and cDNA of Nar1 and comparative studies of strains having or lacking Nar1 have been performed. The deduced amino acid sequence indicates that Nar1 encodes a chloroplast membrane protein with substantial identity to putative formate and nitrite transporters in bacteria. Use of antibodies against NAR1 has corroborated its location in the plastidic membrane. Characterization of strains having or lacking this gene suggests that NAR1 is involved in nitrite transport in plastids, which is critical for cell survival under limiting nitrate conditions, and controls the amount of nitrate incorporated by the cells under limiting CO 2 conditions.

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Nitrite Transport in Chloroplast Inner Envelope Vesicles (I. Direct Measurement of Proton-Linked Transport)

Cited by 62 publications

References 24 publications

Nitrogen assimilation and growth of wheat under elevated carbon dioxide

Nitrogen assimilation and growth of wheat under elevated carbon dioxide

Nitrate assimilation in plant shoots depends on photorespiration

The Chlamydomonas reinhardtii Nar1 Gene Encodes a Chloroplast Membrane Protein Involved in Nitrite Transport

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