Uptake and Reduction of Nitrate: Algae and Fungi

Ullrich, Wolfram R.

doi:10.1007/978-3-642-68885-0_13

Cited by 50 publications

(35 citation statements)

References 107 publications

(106 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is consistent with reductant being th demand of NO3-assimilation. As has been ( several other green algae (22), NR of S. min both NADH and NADPH (data not shown). of NADPH, therefore, may reflect its consun well as nitrite reductase.…”

Section: Dark Carbon Fixation By Pepcsupporting

confidence: 77%

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum

Vanlerberghe

Huppe²,

Vlossak³

et al. 1992

Plant Physiol.

View full text Add to dashboard Cite

Glu, Gln), thus activating respiration to provide carbon for biosynthesis.Less is understood concerning the response of respiration during NO3-assimilation. NO3-must first be reduced to NH4+ via NR and nitrite reductase; in the dark this reduction requires that respiration generate eight electron pairs. Only then is there a demand for ATP and carbon skeletons to assimilate the NH4+ produced from NO3-into amino acids. This paper examines the activation of respiratory carbon flow to support either NO3-or NH4' assimilation. Changes in pyridine nucleotides and the time frame of PK and PEPC activation indicate that the initial demand of NO3-assimilation is reductant. Only subsequently is TCA cycle carbon flow activated to provide carbon skeletons for amino acid synthesis. MATERIALS AND METHODS Organism, Culture, and Experimental ConditionsThe green alga Selenastrum minutum (Naeg.) Collins (UTEX 2459) was grown autotrophically in N-limited chemostats as previously described (23). Experiments were done with cells in the dark as previously described (25), except cells were kept aerobic by continuous bubbling with air. Cells were concentrated to approximately 20 ,ug Chl mL-' for measurements of pyridine nucleotides and to approximately 40 yg Chl-mL-' for other metabolites. NH4Cl or NaNO3 was added to a final concentration of 2 to 5 mm as indicated.The assimilation of inorganic N into amino acids, protein, and nucleic acids requires ATP, reductant power, and carbon skeletons. In the dark, N-limited cells of the green alga Selenastrum minutum must respire endogenous starch reserves to meet these demands (20). Recently, we developed a model for the activation of carbon flow for respiration during the assimilation of NH4+ in S. minutum (21). When N is supplied as NH4', consumption of ATP and carbon skeletons by GS/ GOGAT3 causes changes in several key metabolites (ADP,

show abstract

Section: Dark Carbon Fixation By Pepcsupporting

confidence: 77%

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum

Vanlerberghe

Huppe²,

Vlossak³

et al. 1992

Plant Physiol.

View full text Add to dashboard Cite

show abstract

“…A number of studies on nitrate uptake by cyanobacteria and other microalgae have established that the process is rapidly and effectively inhibited by the presence of ammonium in the outer medium, with the inhibition mediated by ammonium assimilation products (6,18,21). In addition, nitrate utilization by cyanobacteria exhibits a tight dependence upon the rate of CO2 fixation (4,10) and is inhibited by treatment of the cells with DLG, a selective inhibitor of CO2 fixation (16).…”

Section: Methodsmentioning

confidence: 99%

“…Although there is a general belief in the involvement of a nitrate transport system in nitrate utilization, little is known of the biochemistry of nitrate transport in photosynthetic microorganisms and higher plants (1,5,6,18,21). In cyanobacteria, nitrate uptake has been studied by monitoring the disappearance of the anion from the outer medium, and the process has been shown to exhibit saturation kinetics with K, values for nitrate below 50 ,uM (3,6,12,20,22).…”

mentioning

confidence: 99%

Regulated nitrate transport in the cyanobacterium Anacystis nidulans

Lara¹,

Romero²,

Guerrero³

1987

J Bacteriol

View full text Add to dashboard Cite

Intracellular accumulation of nitrate, indicative of the operation of an active nitrate transport system, has been measured in intact cells of the cyanobacterium Anacystis nidulans. The ability of the cells to accumulate nitrate was effectively hindered by either ammonium addition or selective inhibition of CO2 fixation by DL-glyceraldehyde, with the effect of either compound being prevented by previously blocking ammonium assimilation. The results support the contention that nitrate utilization in cyanobacteria is regulated at the level of nitrate transport through the concerted action of animonium assimilation and CO2 fixation.

show abstract

“…There are many reports on the enzyme's repression by ammonia or amino acid nutrition, as well as on its depression, mainly by nitrate and light (4,15).…”

mentioning

confidence: 99%

Synthesis and Degradation of Nitrate Reductase during the Cell Cycle of Chlorella Sorokiniana

Velasco¹,

Tischner²,

Huffaker³

et al. 1989

Plant Physiol.

View full text Add to dashboard Cite

Studies on the diumal variations of nitrate reductase (NR) activity during the life cycle of synchronized Chorela soroklniana cells grown with a 7:5 light-dark cycle showed that the NADH:NR activity, as well as the NR partial activities NADH:cytochrome c reductase and reduced methyl viologen:NR, closely paralleled the appearance and disappearance of NR protein as shown by sodium dodecyl sulfate gel electrophoresis and immunoblots.Results of pulse-labeling experiments with [MS]methionine further confirmed that diumal variations of the enzyme activities can be entirely accounted for by the concomitant synthesis and degradation of the NR protein.

show abstract

Uptake and Reduction of Nitrate: Algae and Fungi

Cited by 50 publications

References 107 publications

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum

Regulated nitrate transport in the cyanobacterium Anacystis nidulans

Synthesis and Degradation of Nitrate Reductase during the Cell Cycle of Chlorella Sorokiniana

Contact Info

Product

Resources

About

Uptake and Reduction of Nitrate: Algae and Fungi

Cited by 50 publications

References 107 publications

Activation of Respiration to Support Dark NO3− and NH4+ Assimilation in the Green Alga Selenastrum minutum

Activation of Respiration to Support Dark NO3− and NH4+ Assimilation in the Green Alga Selenastrum minutum

Regulated nitrate transport in the cyanobacterium Anacystis nidulans

Synthesis and Degradation of Nitrate Reductase during the Cell Cycle of Chlorella Sorokiniana

Contact Info

Product

Resources

About

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum

Activation of Respiration to Support Dark NO₃⁻ and NH₄⁺ Assimilation in the Green Alga Selenastrum minutum