Nitrate reductase activity in tomato and cucumber leaves as influenced by NaCl and n source

The southern Brazilian highland plateau is a mosaic of two contrasting plant communities, Araucaria forests and grasslands, which differ in the relative abundances and spatial patterns of soil nitrate and ammonium. However, we still do not know the inorganic N preferences of one key species in this mosaic, Araucaria angustifolia, the dominant tree species in the Araucaria forests and an important tree species invading the adjacent grasslands. Growth responses measured in a greenhouse study demonstrated that the species prefers NH4+ over NO3- as an inorganic N source. When provided alone, NO3- induced N deficiency symptoms: increases in root: shoot ratio, root branching and leaf mass per area, thickening of the shoot apexes and decreased mass-based chlorophyll and N concentrations of the young leaves. Nitrate-based nutrition also affected the whole plant N and carbon (C) distribution: young leaves accumulated less N and showed a larger C:N ratio than mature leaves. The nitrate reductase activity (NRA) followed the pattern of root: shoot partitioning expected for temperate climate conifers (activity concentrated in roots). However, the presence of NRA even under sole NH4+ nutrition indicates that plants may show constitutive levels of the enzyme, or that low levels of NO3- (possibly formed by contamination of the growth media) can induce leaf NRA. We suggest that A. angustifolia has ammonium as a preferential inorganic N source, and that this preference may favor a more successful establishment in grassland than in forest areas.

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

Zeitschrift für Naturforschung C ◽

10.1515/znc-1991-7-830 ◽

1991 ◽

Vol 46 (7-8) ◽

pp. 703-705 ◽

Cited By ~ 5

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.

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

Biochemical Journal ◽

10.1042/bcj20170115 ◽

2017 ◽

Vol 474 (11) ◽

pp. 1769-1787 ◽

Cited By ~ 5

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.

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