T. A. V. Rees

University of Auckland

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Changes in amino acid composition of Ulva intestinalis (Chlorophyceae) following addition of ammonium or nitrate

Phycologia (2006)

Michael W. Taylor Neill Barr Coral M. Grant T. A. V. Rees

M.W. Taylor, N.G. Barr, C.M. Grant and T.A.V. Rees. 2006. Changes in amino acid composition of Ulva intestinalis (Chlorophyceae) following addition of ammonium or nitrate. Phycologia 45: 270–276. DOI: 10.2216/05-15.1Nitrogen assimilation was investigated in the marine macroalga Ulva intestinalis. Following incubation of the alga in the presence of ammonium or nitrate, resulting changes in free amino acid content were determined. After 10 h, the largest changes by far occurred in the levels of glutamine and asparagine, which both increased more than 10-fold regardless of nitrogen source. Other amino acids increased slightly, but these two – together with their precursors glutamate and aspartate – comprised 83 and 76% of the total free protein amino acid-N pool upon addition of ammonium or nitrate, respectively. In subsequent time-course experiments, with ammonium as nitrogen source, glutamate initially decreased (with a concomitant increase in glutamine) before recovering to at least its original level. Asparagine levels began to increase after 1 h. Saturation of the glutamine and glutamate pools occurred after approximately 6 h, and coincided with the transition from the surge phase of ammonium uptake to the internally controlled uptake phase. This study represents the first investigation into how levels of specific amino acids change during ammonium assimilation in macroalgae, and as such extends our current knowledge of this poorly understood process.

Chlorophyceae

Nitrogen Assimilation

10.2216/05-15.1

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Citations (18)

Diurnal cycle and kinetic of ammonium assimilation in the green alga Ulva pertusa.

HAL (Le Centre pour la Communication Scientifique Directe) (2007)

François Gévaert Neill Barr T. A. V. Rees

Assimilation (phonology)

Diurnal cycle

Source

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Citations (0)

Allometric evidence for the dominant role of surface cells in ammonium metabolism and photosynthesis in northeastern New Zealand seaweeds

Marine Ecology Progress Series (1999)

Michael W. Taylor R Taylor T. A. V. Rees

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 184:73-81 (1999) - doi:10.3354/meps184073 Allometric evidence for the dominant role of surface cells in ammonium metabolism and photosynthesis in northeastern New Zealand seaweeds Michael W. Taylor, Richard B. Taylor, T. Alwyn V. Rees* Leigh Marine Laboratory and Schools of Biological and Environmental and Marine Sciences, University of Auckland, PO Box 349, Warkworth, New Zealand *Addressee for correspondence. E-mail: ta.rees@auckland.ac.nz ABSTRACT: Relationships between seaweed morphology and the metabolism of ammonium and carbon were examined for 9 seaweeds from northeastern New Zealand. Maximum rates of surge ammonium uptake and ammonium assimilation, in addition to the maximum ammonium storage pool, were strongly positively correlated with seaweed surface area:volume (SA:V) ratio when expressed per g dry weight, but were largely independent of SA:V ratio when expressed per cm2 surface area. This suggests that ammonium metabolism may be confined largely to the outermost cell layers. Similar scaling properties were found for rates of photosynthesis and, to a lesser extent, respiration. Rates of photosynthesis were similar to those derived from the literature for northern hemisphere seaweeds, while respiration rates were slightly lower among New Zealand seaweeds. These comparatively minor geographic differences suggest that previously documented differences in rates of ammonium uptake between the 2 regions are not related to carbon metabolism. Maximum rates of ammonium assimilation were determined by measuring the internally controlled rate of ammonium uptake, which closely matched the assimilation rate in the green seaweed Ulva sp., the red seaweed Osmundaria colensoi, and the brown seaweed Zonaria turneriana. KEY WORDS: Ammonium assimilation · Seaweeds · Photosynthesis · Scaling · Ammonium storage · Respiration · Ammonium uptake · Surface area:volume ratio Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 184. Publication date: July 28, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Allometry

10.3354/meps184073

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Citations (17)

The role of nickel in urea assimilation by algae

Planta (1982)

T. A. V. Rees I. A. Bekheet

Phaeodactylum tricornutum

10.1007/bf00393307

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Citations (67)

THE UPTAKE OF UREA BY THE DIATOM, PHAEODACTYLUM

New Phytologist (1979)

T. A. V. Rees P. J. Syrett

S ummary Urea‐grown cells of Phaeodactylum absorbed [ 14 C]urea by an active mechanism. Most of the urea taken up was present in the cells as free urea and the ratio of internal to external concentration could exceed 3000. The activity of the transport mechanism was greatly increased by depriving the cells of nitrogen for up to 24 h. The uptake mechanism had a high affinity for urea, the half‐saturation constant being about 1·0 μM. Active uptake of urea occurred in darkness, particularly in nitrogen‐deprived cells, but uptake was markedly stimulated by light. Uptake was not inhibited by DCMU but was abolished almost completely by 10 −4 m CCCP. It is concluded that active uptake is driven by phosphorylation. Uptake of [ 14 C]urea continued until a constant level within the cells was attained, the plateau value probably resulting from a balance between rate of active uptake and rate of passive loss by diffusion. The transport mechanism was absent from cells grown with ammonium as nitrogen‐source. The urea uptake mechanism developed in such cells when they were deprived of nitrogen; cycloheximide prevented the development of the mechanism. The mechanism was lost when urea‐grown cells were incubated in ammonium medium for 24 h but ammonium (at concentrations up to 10 mM) did not inhibit short‐term uptake of urea into urea‐grown cells.

DCMU

Phaeodactylum tricornutum

10.1111/j.1469-8137.1979.tb07572.x

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Citations (65)

CONTRASTING EFFECTS OF METHIONINE SULFOXIMINE ON UPTAKE AND ASSIMILATION OF AMMONIUM IN ULVA INTESTINALIS (CHLOROPHYCEAE)1

Journal of Phycology (2004)

Neill Barr Rob J. Tijsen T. A. V. Rees

Ammonium is assimilated in algae by the glutamine synthetase (GS)–glutamine:2‐oxoglutarate aminotransferase pathway. In addition to the assimilation of external ammonium taken up across the cell membrane, an alga may have to reassimilate ammonium derived from endogenous sources (i.e. nitrate reduction, photorespiration, and amino acid degradation). Methionine sulfoximine (MSX), an irreversible inhibitor of GS, completely inhibited GS activity in Ulva intestinalis L. after 12 h. However, assimilation of externally derived ammonium was completely inhibited after only 1–2 h in the presence of MSX and was followed by production of endogenous ammonium. However, endogenous ammonium production in U. intestinalis represented only a mean of 4% of total assimilation attributable to GS. The internally controlled rate of ammonium uptake ( V i ) was almost completely inhibited in the presence of MSX, suggesting that V i is a measure of the maximum rate of ammonium assimilation. After complete inhibition of ammonium assimilation in the presence of MSX, the initial or surge ( V s ) rate of ammonium uptake in the presence of 400 μM ammonium chloride decreased by only 17%. However, the amount that the rate of ammonium uptake decreased by was very similar to the uninhibited rate of ammonium assimilation. In addition, the decrease in the rate of ammonium uptake in darkness (in the absence of MSX) in the presence of 400 μM ammonium chloride matched the decrease in the rate of ammonium assimilation. However, in the presence of 10 μM ammonium chloride, MSX completely inhibited ammonium assimilation but had no effect on the rate of uptake.

Ammonium chloride

Assimilation (phonology)

Chlorophyceae

Nitrogen Assimilation

10.1111/j.1529-8817.2004.04004.x

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Citations (11)

The green hydra symbiosis and ammonium. II. Ammonium assimilation and release by freshly isolated symbionts and cultured algae

Proceedings of the Royal Society of London. Series B, Biological sciences (1989)

T. A. V. Rees

Freshly isolated symbionts from the European strain of green hydra containing native (E/E) or heterologous algae (E/3N8, E/NC), and the Wytham strain of green hydra (W5) assimilated ammonium at pH 7 in light. Both nitrogen-replete and nitrogen-starved cultures of high (3N813A) and low (NC64A) maltose-releasing strains of Chlorella also assimilated ammonium at pH 7 in light. However, at pH 4, freshly isolated symbionts from E/E, E/3N8 and W5, and nitrogen-replete cultures of the high maltose-releasing strain 3N813A released ammonium, and the rate of release was stimulated in darkness. Freshly isolated symbionts from the association E/NC released ammonium at pH 4 when incubated in darkness but assimilated ammonium in light. Nitrogen-starved cultures of both high and low maltose-releasing strains assimilated ammonium at pH 4 in both light and dark. Ammonium-assimilation characteristics of nitrogen-starved cultures were sufficiently different from those of freshly isolated symbionts to indicate that symbionts are not maintained by the host under nitrogen deficiency at high pH. A detailed model of symbiont regulation is proposed that suggests that the ammonium compensation point (defined as the pH at which there is no net release or assimilation of ammonium) is important as a homeostatic mechanism for maintaining high rates of maltose release in light and as a mechanism for controlling both symbiont cell division and changes in algal number per digestive cell with changes in environmental conditions. Experimental evidence consistent with the model is presented. Nitrogen-replete cultures of the high maltose-releasing strain 3N813A decreased medium pH during ammonium assimilation and increased medium pH during ammonium release. Furthermore, dark-grown animals of the association E/E released ammonium when transferred to a 12 h light : 12 h dark régime and release was stimulated by the photosynthetic inhibitor 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea.

Assimilation (phonology)

Lernaean Hydra

10.1098/rspb.1989.0005

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Citations (37)

A method for temporal measurement of hemolymph composition in the giant clam symbiosis and its application to glucose and glycerol levels during a diel cycle

Limnology and Oceanography (1993)

T. A. V. Rees William K. Fitt Brett K. Baillie David Yellowlees

A syringe method for taking repeated, small‐volume, in vivo samples of hemolymph from the giant clam Tridacna gigas is described. Hemolymph collected by syringe had similar ionic and protein characteristics to hemolymph from the same clams killed immediately afterward. Glucose concentrations in the hemolymph showed a diurnal increase, with the maximum daytime levels being 3.2‐fold higher than the nighttime minimum. In contrast, the glycerol concentrations were consistently negligible. The method has considerable potential for monitoring metabolic interactions between host and symbiont in this alga‐invertebrate symbiosis.

Hemolymph

Diel vertical migration

10.4319/lo.1993.38.1.0213

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Citations (35)

Sodium Dependent Photosynthetic Oxygen Evolution in a Marine Diatom

Journal of Experimental Botany (1984)

T. A. V. Rees

Photosynthetic oxygen evolution in air-equilibrated cultures of Phaeodactylum tricornutum is dependent on the presence of sodium, but not potassium; sodium cannot be replaced by either potassium, lithium or ammonium. Respiration is not sodium dependent. At constant CO2 concentrations the depression of oxygen evolution in the absence of sodium is more pronounced at pH 8.0 than at pH 6.5 and it is concluded that sodium facilitates the utilization of bicarbonate. Sodium increases the affinity of Phaeodactylum for inorganic carbon as does growth at low inorganic carbon concentrations.

Phaeodactylum tricornutum

Oxygen evolution

10.1093/jxb/35.3.332

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Citations (57)

KINETICS OF AMMONIUM ASSIMILATION IN TWO SEAWEEDS, ENTEROMORPHA SP. (CHLOROPHYCEAE) AND OSMUNDARIA COLENSOI (RHODOPHYCEAE)

Journal of Phycology (1999)

Michael W. Taylor T. A. V. Rees

The kinetics of ammonium assimilation were investigated in two seaweeds from northeastern New Zealand, Enteromorpha sp. (Chlorophyceae, Ulvales) and Osmundaria colensoi (Hook. f. et Harvey) R.E. Norris (Rhodophyceae, Ceramiales), with the use of a recently developed method for measuring assimilation. In contrast to ammonium uptake, which was nonsaturable, ammonium assimilation exhibited Michaelis–Menten kinetics in both species. Maximum rates of assimilation (V max ) were 27 and 12 μmol·(g DW) −1 ·h −1 for Enteromorpha sp. and O. colensoi, respectively, with half‐saturation (K m ) constants for assimilation of 18 and 41 μM. At environmentally relevant concentrations, assimilation accounted for all of the ammonium taken up by both species. The maximum rate of assimilation in Enteromorpha sp. resembled very closely that of the ammonium assimilatory enzyme, glutamine synthetase, when activities of the latter were measured in the presence of subsaturating substrate (glutamate and ATP) concentrations. Moreover, the initial rate of glutamine production (measured with HPLC) following ammonium enrichment was almost identical to the rates determined above. The rate of ammonium assimilation was therefore determined by three independent methods, two of which involve in vivo measurements, and it is suggested that the use of assimilation kinetics may be useful when examining the nutrient relations of seaweeds.

Chlorophyceae

Assimilation (phonology)

Ceramiales

Nitrogen Assimilation

10.1046/j.1529-8817.1999.3540740.x

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Citations (48)