scholarly journals Pre-mature senescence in the oldest leaves of low nitrate-grown Atxdh1 mutant uncovers a role for purine catabolism in plant nitrogen metabolism

2017 ◽  
Author(s):  
Aigerim Soltabayeva ◽  
Sudhakar Srivastava ◽  
Assylay Kurmanbayeva ◽  
Aizat Bekturova ◽  
Robert Fluhr ◽  
...  
Keyword(s):  
Protein Degradation ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Organic N ◽  
Oxygen Species ◽  
Wild Type ◽  
Plant Nitrogen ◽  
Purine Catabolism ◽  
Early Leaf Senescence

ABSTRACTThe nitrogen rich ureides allantoin and allantoate, are known to play a role in nitrogen delivery in Leguminosae, in addition to their role as reactive oxygen species scavengers. However, their role as a nitrogen source in non-legume plants has not been shown. Xanthine dehydrogenase1 (AtXDH1) activity is a catalytic bottleneck step in purine catabolism. Atxdh1 mutant exhibited early leaf senescence, lower soluble protein and organic-N levels as compared to wild-type (WT) older leaves when grown with 1 mM nitrate, whereas under 5mM, mutant plants were comparable to WT. Similar nitrate-dependent senescence phenotypes were evident in the older leaves of allantoinase (Ataln) and allantoate amidohydrolase (Ataah) mutants, impaired in further downstream steps of purine catabolism. Importantly, under low nitrate conditions, xanthine was accumulated in older leaves of Atxdh1, whereas allantoin in both older and younger leaves of Ataln but not in WT leaves, indicating remobilization of xanthine degraded products from older to younger leaves. Supporting this notion, ureide transporters UPS1, UPS2 and UPS5 were enhanced in older leaves of 1 mM nitrate-fed WT as compared to 5 mM. Enhanced AtXDH, AtAAH and purine catabolic transcripts, were detected in WT grown in low nitrate, indicating regulation at protein and transcript levels. Higher nitrate reductase activity in Atxdh1 than WT leaves, indicates their need for nitrate assimilation products. It is further demonstrated that the absence of remobilized purine-degraded N from older leaves is the cause for senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of nitrate starved Atxdh1 plants.SummaryThe absence of remobilized purine-degraded N from older to the young growing leaves is the cause for senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of nitrate starved Atxdh1 plants.

Nitrate Reductase from a Mutant Strain of Chlamydomonas reinhardii Incapable of Nitrate Assimilation

1983 ◽  
Vol 38 (5-6) ◽  
pp. 439-445 ◽  
Author(s):  
Emilio Fernández ◽  
Jacobo Cárdenas
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Wild Strain ◽  
Nitrate Assimilation ◽  
Pyridine Nucleotide ◽  
Spectral Studies ◽  
Binding Region ◽  
Chlamydomonas Reinhardii ◽  
Blue Sepharose

Nitrate reductase from mutant 305 of Chlamydomonas reinhardii has been purified about 90-fold and biochemically characterized. The enzyme can use reduced flavins and viologens as electron donors to reduce nitrate but, unlike the nitrate reductase complex from its parental wild strain, lacks NAD(P)H-nitrate reductase and NAD(P)H-cytochrome c reductase activities, does not bind to Blue-Agarose or Blue-Sepharose and exhibits a significantly lower molecular weight (177.000 vs. 241.000), whereas its kinetic characteristics and its sensitivity against several inhibitors and treatments are very similar to those of the terminal nitrate reductase activity of the wild strain complex. Spectral studies and antagonistic experiments with tungstate show the presence of cytochrome b557 and molybdenum. These facts lead us to propose that nitrate reductase from mutant 305 has a protein deletion which affects the pyridine nucleotide binding region of the diaphorase protein but without any effect on the terminal nitrate reductase activity.

The relation between nitrate reductase activity and grain nitrogen productivity in wheat

1975 ◽  
Vol 26 (1) ◽  
pp. 1 ◽  
Author(s):  
MJ Dalling ◽  
GM Halloran ◽  
JH Wilson
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Selection Criterion ◽  
Activity Levels ◽  
Plant Nitrogen ◽  
Nitrogen Productivity ◽  
Nitrogen Redistribution ◽  
Total Plant ◽  
Grain Nitrogen

The seasonal patterns of leaf nitrate reductase activity were compared in five wheat cultivars which differ widely in their capacities to accumulate grain nitrogen. Significant differences in the average levels of nitrate reductase activity were observed between cultivars. Total seasonal nitrate reductase activity was closely related to total plant nitrogen at maturity. Grain nitrogen was only related to total seasonal nitrate reductase activity when allowance was made for significant differences between cultivars in nitrogen redistribution patterns. The significance of these results with respect to the possible use of nitrate reductase activity levels as a selection criterion for nitrogen productivity is discussed.

Seasonal variation in nitrate reductase activity in needles of high-elevation red spruce trees

1992 ◽  
Vol 22 (3) ◽  
pp. 375-380 ◽  
Author(s):  
M.G. Tjoelker ◽  
S.B. McLaughlin ◽  
R.J. DiCosty ◽  
S.E. Lindberg ◽  
R.J. Norby
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
High Elevation ◽  
Preliminary Evidence ◽  
Air Pollutant ◽  
Red Spruce ◽  
Acid Vapor ◽  
Assimilation Capacity

To assess seasonal and site variation in foliar nitrate reductase activity and its utility as a biochemical marker for the uptake of nitrogen oxide pollutants in high-elevation forests, we measured nitrate reductase activity in current-year needles of red spruce (Picearubens Sarg.) saplings at two high-elevation stands (1935 and 1720 m) in the Great Smoky Mountains, North Carolina. Measurements spanned two growing seasons between September 1987 and September 1988. Nitrate reductase activity peaked near 60 nmol•g−1•h−1 at both sites in September and October 1987 and August 1988 and declined 80% in November 1987 and 65% in September 1988. Although nitrate reductase activity was 30% greater in saplings at the higher site relative to the lower site in September and October 1987, activity dropped to approximately 10 nmol•g−1•h−1 at both sites in November 1987. No differences among sites were evident the following year. Comparing deposition of nitric acid vapor at a nearby site to nitrate reductase activity suggests that needle nitrate reductase activity is not an unequivocal marker for foliar uptake of nitrogen oxides during air pollutant episodes. The changes in soil nitrate levels in this system provide preliminary evidence that foliar nitrate assimilation may, in part, include nitrate taken up from the soil, as the highest activity occurred during periods of higher A-horizon nitrate concentrations in 1988. These measurements of nitrate reductase activity suggest that red spruce are capable of assimilating nitrate in foliage in the field and that the nitrate assimilation capacity varies throughout the year.

Nitrogen Uptake of Field-grown Cotton. II. Nitrate Reductase Activity and Petiole Nitrate Concentration as Indicators of Plant Nitrogen Status

1983 ◽  
Vol 19 (1) ◽  
pp. 103-109 ◽  
Author(s):  
D. M. Oosterhuis ◽  
G. C. Bate
Keyword(s):  
Nitrate Reductase ◽  
Seasonal Changes ◽  
Nitrate Reductase Activity ◽  
Nitrate Concentration ◽  
Reductase Activity ◽  
Soil N ◽  
Plant Nitrogen ◽  
Petiole Nitrate Concentration ◽  
Leaf Nitrate ◽  
N Status

SUMMARYThe possibility of using seasonal changes in leaf nitrate reductase activity (NRA) as a reliable and sensitive indicator of plant nitrogen (N) status has been investigated in field-grown cotton. These changes were compared with those in nitrate concentration in petioles and variations in soil-N concentration. We conclude that NRA in the uppermost, fully-expanded sympodial leaves may provide a more convenient, sensitive and reliable indicator of plant-N status than measurements of nitrate concentrations in petioles.

scholarly journals 137 Nitrate Assimilation and Carbon-14 Partitioning between Shoots and Roots of Tall Fescue

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 413B-413 ◽  
Author(s):  
W. Michael Sullivan ◽  
Zhongchun Jiang ◽  
Richard J. Hull
Keyword(s):  
Nutrient Solution ◽  
Tall Fescue ◽  
Nitrite Reductase ◽  
Nitrate Reduction ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Organic N ◽  
Fixed Carbon ◽  
Photosynthate Partitioning ◽  
Carbon 14

Efficient use of nitrogen by turfgrasses depends on the ability of roots to absorb and assimilate nitrate. If a larger amount of nitrate is assimilated in the roots than in the shoots and organic N is transported to shoots as needed, nitrogen loss through clipping removal would be reduced. However, the ability of roots to assimilate nitrate depends on carbohydrate supply from the shoots. Our study examined the relationship between nitrate assimilation and photosynthate partitioning between shoots and roots of tall fescue grown in nutrient solution. To alter the pattern of nitrate reduction and photosynthate partitioning, we treated the plants as follows: 1) nutrient solution was aerated and nitrate was supplied to the roots, 2) nutrient solution was not aerated and nitrate was supplied to the roots, 3) nutrient solution was aerated and nitrogen was supplied to the leaves as nitrate, and 4) nutrient solution was aerated, and nitrogen was supplied to the leaves as urea. Photosynthate partitioning was assessed using carbon-14 as a tracer. Nitrate and nitrite reductase activities were determined by in vivo methods. Fortyeight hours after the grass leaves were exposed to carbon-14, >60% of the fixed carbon was translocated to stems and >15% to roots. Foliar application of urea resulted in less export of fixed carbon from leaves and lower leaf nitrite reductase activity than when nitrate was supplied to leaves. Less than 5% of the plant total nitrate reduction was attributed to root based activity. Root aeration decreased root nitrate reductase activity. Our results suggest that root-zone aeration and foliar N application could affect total nitrate assimilation and photosynthate partitioning to roots.

No Correlation between Plasmid Content and Ability to Reduce Nitrate in Wild-Type Strains of Rhodobacter capsulatus

1991 ◽  
Vol 46 (7-8) ◽  
pp. 703-705 ◽  
Author(s):  
Astrid Witt ◽  
Jobst-Heinrich Klemme
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Rhodobacter Capsulatus ◽  
Reductase Activity ◽  
Large Plasmid ◽  
Wild Type ◽  
Plasmid Content ◽  
Phototrophic Bacterium ◽  
N Source ◽  
Type Strains

Patterns of endogenous plasmids and nitrate reductase activities were analyzed in the phototrophic bacterium Rhodobacter (Rb.) capsulatus. From 10 strains investigated (including a UV-induced plasmidless nit- mutant), 4 were unable to grow photosynthetically with nitrate as N-source and lacked nitrate reductase activity (nit strains). Irrespective of the nit phenotype, all wildtype strains contained at least one large plasmid with a size ranging from 93 to 134 kb. Thus, other than in plasmid- cured mutants (J. C. Willison, FEMS Microbiol. Lett. 66, 23-28[1990]), in wild-type strains of Rb. capsulatus the nit- character was not related to lack of endogenous plasmids.

Contribution of the Root System to Nitrate Assimilation in Whole Cotton Plants.

1977 ◽  
Vol 4 (5) ◽  
pp. 811 ◽  
Author(s):  
JW Radin
Keyword(s):  
Nitrate Reductase ◽  
Root Growth ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Physiological Role ◽  
Nitrate Assimilation ◽  
Relative Magnitude ◽  
Balance Sheets ◽  
Cotton Plants ◽  
Reduced Nitrogen

Cotton (Gossypium hirsutum L.) is a species in which most nitrate is assimilated in the green shoot. A physiological role for the small amount of nitrate reductase activity in the roots can be questioned on the basis of relative magnitude. In this investigation, cotton plants were grown on nutrient solutions containing either 1 or 5 mM nitrate, and balance sheets were developed for the transport and metabolism of nitrate and reduced nitrogen in the root and shoot during exponential growth. At either nitrate level, assimilation in the roots was adequate to supply all the nitrogen for root growth. However, some of the reduced nitrogen was exported in the xylem, leaving a net deficit of about 10% at 1 mM nitrate and 36% at 5 mM nitrate. This deficit was presumably satisfied by reduced nitrogen from the shoot. Thus, at these two nitrate concentrations, root growth apparently depended more upon nitrogen assimilated in the roots themselves than upon nitrogen from the shoot. The different fates of nitrogen assimilated in the root and in the shoot may be related to the demonstrated differential regulation of nitrate reductase activity in these two sites.

scholarly journals Transcriptional and translational adaptation to aerobic nitrate anabolism in the denitrifier Paracoccus denitrificans

2017 ◽  
Vol 474 (11) ◽  
pp. 1769-1787 ◽  
Author(s):  
Victor M. Luque-Almagro ◽  
Isabel Manso ◽  
Matthew J. Sullivan ◽  
Gary Rowley ◽  
Stuart J. Ferguson ◽  
...  
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Mutational Analysis ◽  
Paracoccus Denitrificans ◽  
Reductase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Nitrate Assimilation ◽  
Transcriptional Unit ◽  
Regulation Mechanism ◽  
N Source

Transcriptional adaptation to nitrate-dependent anabolism by Paracoccus denitrificans PD1222 was studied. A total of 74 genes were induced in cells grown with nitrate as N-source compared with ammonium, including nasTSABGHC and ntrBC genes. The nasT and nasS genes were cotranscribed, although nasT was more strongly induced by nitrate than nasS. The nasABGHC genes constituted a transcriptional unit, which is preceded by a non-coding region containing hairpin structures involved in transcription termination. The nasTS and nasABGHC transcripts were detected at similar levels with nitrate or glutamate as N-source, but nasABGHC transcript was undetectable in ammonium-grown cells. The nitrite reductase NasG subunit was detected by two-dimensional polyacrylamide gel electrophoresis in cytoplasmic fractions from nitrate-grown cells, but it was not observed when either ammonium or glutamate was used as the N-source. The nasT mutant lacked both nasABGHC transcript and nicotinamide adenine dinucleotide (NADH)-dependent nitrate reductase activity. On the contrary, the nasS mutant showed similar levels of the nasABGHC transcript to the wild-type strain and displayed NasG protein and NADH–nitrate reductase activity with all N-sources tested, except with ammonium. Ammonium repression of nasABGHC was dependent on the Ntr system. The ntrBC and ntrYX genes were expressed at low levels regardless of the nitrogen source supporting growth. Mutational analysis of the ntrBCYX genes indicated that while ntrBC genes are required for nitrate assimilation, ntrYX genes can only partially restore growth on nitrate in the absence of ntrBC genes. The existence of a regulation mechanism for nitrate assimilation in P. denitrificans, by which nitrate induction operates at both transcriptional and translational levels, is proposed.

scholarly journals A Novel Gene (narM) Required for Expression of Nitrate Reductase Activity in the Cyanobacterium Synechococcus elongatus Strain PCC7942

2004 ◽  
Vol 186 (7) ◽  
pp. 2107-2114 ◽  
Author(s):  
Shin-ichi Maeda ◽  
Tatsuo Omata
Keyword(s):  
Nitrate Reductase ◽  
Structural Gene ◽  
Nitrate Reductase Activity ◽  
Insertional Mutagenesis ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Gene Cassette ◽  
Synechococcus Elongatus ◽  
Prosthetic Group ◽  
Functional Link

ABSTRACT A new class of mutants deficient in nitrate assimilation was obtained from the cyanobacterium Synechococcus elongatus strain PCC7942 by means of random insertional mutagenesis. A 0.5-kb genomic region had been replaced by a kanamycin resistance gene cassette in the mutant, resulting in inactivation of two genes, one of which was homologous to the recently characterized cnaT gene of Anabaena sp. strain PCC7120 (J. E. Frías, A. Herrero, and E. Flores, J. Bacteriol. 185:5037-5044, 2003). While insertional mutation of the cnaT homolog did not affect expression of the nitrate assimilation operon or the activity of the nitrate assimilation enzymes in S. elongatus, inactivation of the other gene, designated narM, resulted in specific loss of the cellular nitrate reductase activity. The deduced NarM protein is a hydrophilic protein consisting of 161 amino acids. narM was expressed constitutively at a low level. The narM gene has its homolog only in the cyanobacterial strains that are capable of nitrate assimilation. In most of the cyanobacterial strains, narM is located downstream of narB, the structural gene of the cyanobacterial nitrate reductase, suggesting the functional link between the two genes. NarM is clearly not the structural component of the cyanobacterial nitrate reductase. The narM insertional mutant normally expressed narB, indicating that narM is not the transcriptional regulator of the structural gene of nitrate reductase. These results suggested that narM is required for either synthesis of the prosthetic group of nitrate reductase or assembly of the prosthetic groups to the NarB polypeptide to form functional nitrate reductase in cyanobacteria.

Light Dependent Ammonium Inhibition of Nitrate Assimilation in Rhodopseudomonas capsulata AD2

1984 ◽  
Vol 39 (1-2) ◽  
pp. 85-89 ◽  
Author(s):  
Kassem Alef
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Inhibitory Effect ◽  
Cellular Level ◽  
Rhodopseudomonas Capsulata ◽  
Marked Contrast ◽  
Photosynthesis And Respiration

Abstract Nitrate assimilation by Rhodopseudomonas capsulata AD2 was completely inhibited by ammonium only in young well illuminated cultures. At higher densities (A660 about 0.5) the addition of ammonium had no inhibitory effect, but the nitrate was only reduced to the level of nitrite, which appeared in the medium. Under both conditions the cellular level of nitrate reductase activity remained unaffected. In marked contrast to other R. capsulata strains both ammonium sensitive and insensitive cells could reduce nitrate in the light and in the darkness. In the light up to 90% of the reduced nitrate was assimilated, but in the dark the reduced nitrate was stoichiometrically excreted as nitrite. This behaviour was only shown by R. capsulata AD2 and BK5, while in other strains the nitrate assimilation was always completely inhibited by ammonium. The role of photosynthesis and respiration by the regulation of nitrate reduction is discussed.

Sign in / Sign up

Export Citation Format

Share Document