Siderophores, the iron nutrition of plants, and nitrate reductase

Castignetti, Domenic; John, Sabu

doi:10.1016/0014-5793(86)81100-0

Cited by 49 publications

(16 citation statements)

References 47 publications

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“…Azuara and Aparicio (1983) showed that rates of nitrite excretion were high under high light and low CO2 conditions in Chlamydomonas reinhardtii and suggested that .nitrate might be acting as an electron acceptor under these conditions to adjust levels of reducing power in the cells. Castignetti and Smarrelli (1986) have suggested that NR may be involved in reducing siderophores which are responsible for acquiring metals (e.g. iron) for cell nutrition.…”

Section: Discussionmentioning

confidence: 99%

Nitrate reductase activity quantitatively predicts the rate of nitrate incorporation under steady state light limitation: A revised assay and characterization of the enzyme in three species of marine phytoplankton

Berges

Harrison

1995

Limnology & Oceanography

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The enzyme nitrate reductase (NR) has been proposed as an index of nitrate incorporation rates in marine phytoplankton, but it has proven difficult to interpret NR measurements in field settings because many previous NR assays have been poorly optimized and NR activity in phytoplankton has been poorly characterized under steady state conditions. An NR assay was developed for the diatom Thalassiosira pseudonana using an extraction in phosphate buffer with Triton X-100, EDTA, dithiothreitol, polyvinyl pyrrolidone, and bovine serum albumin. NR activity in homogenates was stable for up to 1 h, but filtered samples could be stored for 96 h in liquid nitrogen without significant loss of activity. Addition of FAD to crude extracts of T. pseudonana had no effect, whereas the effect on desalted extracts or crude extracts from other species, varied from decreases in NR activity to over 250% increases. Half-saturation constants (K,) varied between species; high levels of NADH or nitrate were found to be inhibitory in some cases. These results indicate a wide diversity of forms of NR in marine phytoplankton.Under continuous, light-limited growth, NR activity was quantitatively related to calculated rates of nitrate incorporation (pN) in T. pseudonana, Skeletonema costatum, and three other diatom species examined. The relationship differed for 10 other species; NR activity was equal to bN in some cases, but higher or lower in others. In dinoflagellates, in particular, NR activity was highly correlated with pN, but accounted for ~20% of hN in Amphidinium carterae.The importance of nitrogen metabolism in general, and nitrate metabolism in particular, in the marine environment is based not only on the frequent identification of nitrogen as a nutrient limiting primary production, but also because of the important differences between the fate of production depending on whether newly available nitrogen (e.g. nitrate) or regenerated forms (e.g. ammonium) are used (Dugdale and Goering 1967;Platt et al. 1992). Thus, measurements of rates of nitrate incorporation (sensu Wheeler 1983, i.e. the combination of inorganic nitrogen into large macromolecules such as proteins and nucleic acids) by marine phytoplankton are critical to understanding rates of primary production and biogeochemical cycling in many areas of the oceans.Current methods of estimating rates of nitrate incorporation are based largely on incubation techniques with the stable isotope 15N as a tracer (Dugdale and Wilkerson 1986). It is appreciated that there are problems with this

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Section: Discussionmentioning

confidence: 99%

Nitrate reductase activity quantitatively predicts the rate of nitrate incorporation under steady state light limitation: A revised assay and characterization of the enzyme in three species of marine phytoplankton

Berges

Harrison

1995

Limnology & Oceanography

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“…exchangeable iron in circumneutral soils), must be overcome by another mechanism in plants with a high cation-exchange capacity. DiflFerent mechanisms that may render iron available to (rooting) plants are reviewed by Uren (1984) or Castignetti & Smarrelli (1986).…”

Section: Discussionmentioning

confidence: 99%

Cation‐exchange properties and adaptation to soil acidity in bryophytes

1990

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SUMMARYCation-exchange processes of plant tissue are often hypothesized to affect ion uptake. Fixation of cations on exchange sites could either withdraw cations from further uptake, or concentrate them for the absorption sites. For a number of bryophyte taxa (Atrichum undulatum (Hedw.) P. Beauv., Homalothecium sericeum (Hedw.) B.S.&G., Leucohryum glaucum (Hedw.) Angstr., Mniiim hornum Hedw., Plagiomnium undulatum (Hedw.) T. Kop., Polytrichum formosum Hedw.), these contrasting hypotheses were tested by studying cation-exchange properties and soil preference of populations with respect to soil acidity and soil exchangeable cations (Al, H, Fe, Mn, Ca, Mg, K). Acidiphilous and acidicline taxa (preference for soils with pH < 5) with relatively lower cation-exchange capacities tolerate high exchangeable aluminium levels and low calcium levels. Neutrocline taxa (preference for soils with pH > 5) with higher cation-exchange capacity avoid aluminium in the substrate and thrive on calciumrich substrates. Cation-exchange properties therefore do not protect mosses against potentially toxic cations such as aluminium through a sequestration mechanism. However cation exchange sites may increase the availability of cations. High cation-exchange capacity was indeed shown to favour fixation of aluminium over calcium ions and hence a low capacity is a prerequisite for taxa adapted to acid soils.

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“…Phenolics are secreted from Fe-deficient plants to mobilize apoplastic Fe (Jin et al 2007). For acquisition of iron from Fe(III)-humate (Cesco et al 2002) and Fe(III)-siderophores (Castignetti and Smarrelli 1986), and Fe(III)(OH) 3 in Strategy-I plants, the Fe(III) must first be reduced to Fe 2+ by protons in the root cell membranes by AtFRO2 (Robinson et al 1999) and PsFRO1 (Waters et al 2002) and transferred into the root cells by IRT1 (Eide et al 1996).…”

Section: Fe-chelate Complexes In Xylem Sapmentioning

confidence: 99%

Chemical forms of iron in xylem sap from graminaceous and non-graminaceous plants

Ariga

Hazama

Yanagisawa

et al. 2014

Soil Science and Plant Nutrition

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Graminaceous plants can take up iron-phytosiderophore complexes, whereas non-graminaceous plants absorb ferrous ions after the reduction of ferric compounds at the root cell membranes. The iron (Fe) in the roots may be transported to the aerial plant parts through the xylem. We compared the chemical forms in xylem sap collected from the cut stems of three graminaceous .]) grown in composite soils for the concentrations of iron and iron-chelating compounds (nicotianamine, phytosiderophores, citrate). We also fractionated the xylem saps by size-exclusion chromatography to gain insight into the chemical forms of iron. The Fe concentrations in the xylem sap ranged from 9 to 40 μM. Nicotianamine was found in the xylem sap from all the plants examined, with higher concentrations in the non-graminaceous plants. In contrast, phytosiderophores (2'-deoxymugineic acid and mugineic acid) were predominantly detected in the graminaceous plants. The concentrations of free citrate varied greatly (from 4 to 2200 μM) among the six plant species. The xylem sap iron in non-graminaceous plants may form two types of Fe-citrate, whereas in graminaceous plants, the bound Fe forms may be largely two types of Fe-citrate with various Fe-phytosiderophores.

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Siderophores, the iron nutrition of plants, and nitrate reductase

Cited by 49 publications

References 47 publications

Nitrate reductase activity quantitatively predicts the rate of nitrate incorporation under steady state light limitation: A revised assay and characterization of the enzyme in three species of marine phytoplankton

Nitrate reductase activity quantitatively predicts the rate of nitrate incorporation under steady state light limitation: A revised assay and characterization of the enzyme in three species of marine phytoplankton

Cation‐exchange properties and adaptation to soil acidity in bryophytes

Chemical forms of iron in xylem sap from graminaceous and non-graminaceous plants

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