Regulation of Nitrate Reductase during Early Seedling Growth (A Role for Asparagine and Glutamine)

Sivasankar, S.; Oaks, Ann

doi:10.1104/pp.107.4.1225

Cited by 56 publications

(30 citation statements)

References 23 publications

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“…The demands of carbon fixation for reductant might limit this malate shuttle. Second, the reduction of NO 2 Ϫ to NH 4 ϩ , the incorporation of NH 4 ϩ into amino acids, and the Calvin cycle all occur in the stroma of a chloroplast (32) and require ferredoxin that is reduced via photosynthetic electron transport (33). Elevated CO 2 stimulates the Calvin cycle and, under light-limited conditions, can diminish the amount of reduced ferredoxin available for NO 2 Ϫ reduction or NH 4 ϩ assimilation (34,35).…”

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.

189

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.

189

173

View full text Add to dashboard Cite

show abstract

“…As a result, elevated CO 2 concentrations inhibited NO 2 Ϫ transport into the chloroplast (15). (ii) Several competing processes, the C 3 reductive photosynthetic carbon cycle, the reduction of NO 2 Ϫ to NH 4 ϩ , and the incorporation of NH 4 ϩ into amino acids, occur in the chloroplast stroma (46) and require reduced ferredoxin generated by photosynthetic electron transport (47). Key enzymes in these processes have different affinities for reduced ferredoxin: ferredoxin-NADP reductase has a K m of 0.1 M, nitrite reductase has a K m of 0.6 M, and glutamate synthase has a K m of 60 M (48).…”

Section: Discussionmentioning

confidence: 99%

Nitrate assimilation in plant shoots depends on photorespiration

Rachmilevitch

Cousins

Bloom

2004

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

276

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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“…Nitrogen (N) concentration was determined using the Kjeldahl method (Sivasankar and Oaks, 1995). Phosphorous (P) was analyzed by a vanadate molybdate method using an UV/visible spectrophotometer following Chapman and Pratt (1962).…”

Section: Variable Determinationsmentioning

confidence: 99%

Alleviation of Drought Stress in White Clover after Inoculation with Arbuscular Mycorrhizal Fungi

Tuo

Zou

2017

Not Bot Horti Agrobo

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White clover is extremely susceptive to drought stress (DS), while it is not clear whether arbuscular mycorrhizal fungi (AMF) enhance drought tolerance of the plant. This study was carried out to evaluate effects of two AMF species, Funneliformis mosseae and Paraglomus occultum, on flavonoid, soluble protein, proline, and nutrient uptake in roots of white clover under well-watered (WW) and DS conditions. Root colonization by F. mosseae and P. occultum was heavily decreased by 7-week DS treatment. Mycorrhizal plants showed considerably greater biomass production in shoot, root, and total (shoot+root) than non-mycorrhizal plants, irrespective of soil water status. AMF inoculation led to significantly higher root soluble protein and proline accumulation under WW and DS and root flavonoid level under DS, regardless of AMF species. Root N, P, K and Cu concentrations were dramatically increased by mycorrhization under WW and DS, and root Ca, Mg, Fe, and Mn levels were significantly higher in AMF plants than in non-AMF plants under WW. It concluded that AMF strongly enhanced plant growth and drought tolerance of white clover by greater nutrient absorption and protective substances (soluble protein, proline, and flavonoid) accumulation.

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Regulation of Nitrate Reductase during Early Seedling Growth (A Role for Asparagine and Glutamine)

Cited by 56 publications

References 23 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

Alleviation of Drought Stress in White Clover after Inoculation with Arbuscular Mycorrhizal Fungi

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