Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.7.1.2 (nitrate reductase)
3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because of controversies in the literature on nitric oxide (NO) production by plants, NO detection by the frequently used diaminofluorescein (DAF-2 and DAF-2DA) and by chemiluminescence were compared using the following systems of increasing complexity: (i) dissolved NO gas; (ii) the NO donor sodium nitroprusside (SNP); (iii) purified nitrate reductase (NR); and (iv) tobacco cell suspensions. Low (physiological) concentrations (< or =1 nM) of dissolved NO could be precisely quantified by chemiluminescence, but caused no DAF-2 fluorescence. In contrast to NO gas, SNP, NR, or cell suspensions produced both good DAF fluorescence and chemiluminescence signals which were completely (chemiluminescence) or partly (DAF fluorescence) prevented by NO scavengers. Signal strength ratios between the two methods were variable depending on the NO source, and eventually reflect variable NO oxidation. DAF fluorescence in cell suspension cultures was also increased by an as yet unidentified compound(s) released from cells into the medium. These compounds gave no chemiluminescence signal and were not produced by NR-free mutants. Their production was stimulated by anoxia, by inhibitors of mitochondrial electron transport, and by the fungal elicitor cryptogein. Thus, changes in DAF fluorescence are not necessarily indicative for NO production, but may also reflect NO oxidation and/or production of other DAF-reactive compounds.
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PMID:Nitric oxide (NO) detection by DAF fluorescence and chemiluminescence: a comparison using abiotic and biotic NO sources. 1689 78

Nitric oxide (NO) functions in various physiological and developmental processes in plants. However, the source of this signaling molecule in the diversity of plant responses is not well understood. It is known that NO mediates auxin-induced adventitious and lateral root (LR) formation. In this paper, we provide genetic and pharmacological evidence that the production of NO is associated with the nitrate reductase (NR) enzyme during indole-3-butyric acid (IBA)-induced lateral root development in Arabidopsis thaliana L. NO production was detected using 4,5-diaminofluorescein diacetate (DAF-2DA) in the NR-deficient nia1, nia2 and Atnoa1 (former Atnos1) mutants of A. thaliana. An inhibitor for nitric oxide synthase (NOS) N(G)-monomethyl-l-arginine (l-NMMA) was applied. Our data clearly show that IBA increased LR frequency in the wild-type plant and the LR initials emitted intensive NO-dependent fluorescence of the triazol product of NO and DAF-2DA. Increased levels of NO were restricted only to the LR initials in contrast to primary root (PR) sections, where NO remained at the control level. The mutants had different NO levels in their control state (i.e. without IBA treatment): nia1, nia2 showed lower NO fluorescence than Atnoa1 or the wild-type plant. The role of NR in IBA-induced NO formation in the wild type was shown by the zero effects of the NOS inhibitors l-NMMA. Finally, it was clearly demonstrated that IBA was able to induce NO generation in both the wild-type and Atnoa1 plants, but failed to induce NO in the NR-deficient mutant. It is concluded that the IBA-induced NO production is nitrate reductase-associated during lateral root development in A. thaliana.
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PMID:Exogenous auxin-induced NO synthesis is nitrate reductase-associated in Arabidopsis thaliana root primordia. 1793 9

Nitric oxide (NO) is a gas displaying multiple physiological functions in plants, animals and bacteria. The enzymes nitrate reductase and NO synthase have been suggested to be involved in the production of NO in plants and algae, but the implication of those enzymes in NO production under physiological conditions remains obscure. Symbiodinium microadriaticum, commonly referred to as zooxanthellae, is a marine microalga commonly found in symbiotic association with a cnidarian host including reef-building corals. Here we demonstrate NO production in zooxanthellae upon supplementation of either sodium nitrite or L-arginine as a substrate. The nitrite-dependent NO production was detected electrochemically and confirmed by the application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a specific NO scavenger. Cells stained with the diaminofluorescein, DAF-2 DA, an NO fluorescent probe, showed an increase in fluorescence intensity upon supplementation of both sodium nitrite and L-arginine. Microscopic observations of DAF-stained cells verified that NO was produced inside the cells. NO production in S. microadriaticum was found to increase upon exposure of cells to an acute heat stress which also caused a decline in the photosynthetic efficiency of PSII (F(v)/F(m)). This study provides substantial evidence to confirm that zooxanthellae can synthesize NO even when they are not in a symbiotic association with a coral host. The increase in NO production at high temperatures suggests that heat stress stimulates the microalgal NO production in a temperature-dependent manner. The implications of these findings are discussed in the light of the coral bleaching phenomenon which is associated with elevated sea surface temperature due to global warming.
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PMID:Heat stress stimulates nitric oxide production in Symbiodinium microadriaticum: a possible linkage between nitric oxide and the coral bleaching phenomenon. 1830 60

Vascular tissue was recently shown to be capable of producing nitric oxide (NO), but the production sites and sources were not precisely determined. Here, NO synthesis was analysed in the phloem of Vicia faba in response to stress- and pathogen defence-related compounds. The chemical stimuli were added to shallow paradermal cortical cuts in the main veins of leaves attached to intact plants. NO production in the bare-lying phloem area was visualized by real-time confocal laser scanning microscopy using the NO-specific fluorochrome 4,5-diaminofluorescein diacetate (DAF-2 DA). Abundant NO generation in companion cells was induced by 500 microm salicylic acid (SA) and 10 microm hydrogen peroxide (H(2)O(2)), but the fungal elicitor chitooctaose was much less effective. Phloem NO production was found to be dependent on Ca(2+) and mitochondrial electron transport and pharmacological approaches found evidence for activity of a plant NO synthase but not a nitrate reductase. DAF fluorescence increased most strongly in companion cells and was occasionally observed in phloem parenchyma cells. Significantly, accumulation of NO in sieve elements could be demonstrated. These findings suggest that the phloem perceives and produces stress-related signals and that one mechanism of distal signalling involves the production and transport of NO in the phloem.
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PMID:Nitric oxide generation in Vicia faba phloem cells reveals them to be sensitive detectors as well as possible systemic transducers of stress signals. 1831 39

The nitrate reductase (NR)-defective double mutant of Arabidopsis thaliana (nia1 nia2) has previously been shown to present a low endogenous content of NO in its leaves compared with the wild-type plants. In the present study, we analyzed the effect of NR mutation on floral induction and development of A. thaliana, as NO was recently described as one of the signals involved in the flowering process. The NO fluorescent probes diaminofluorescein-2 diacetate (DAF-2DA) and 1,2-diaminoanthraquinone (1,2-DAA) were used to localize NO production in situ by fluorescence microscopy in the floral structures of A. thaliana during floral development. Data were validated by incubating the intact tissues with DAF-2 and quantifying the DAF-2 triazole by fluorescence spectrometry. The results showed that NO is synthesized in specific cells and tissues in the floral structure and its production increases with floral development until anthesis. In the gynoecium, NO synthesis occurs only in differentiated stigmatic papillae of the floral bud, and, in the stamen, only anthers that are producing pollen grains synthesize NO. Sepals and petals do not show NO production. NR-deficient plants emitted less NO, although they showed the same pattern of NO emission in their floral organs. This mutant blossomed precociously when compared with wild-type plants, as measured by the increased caulinar/rosette leaf number and the decrease in the number of days to bolting and anthesis, and this phenotype seems to result from the markedly reduced NO levels in roots and leaves during vegetative growth. Overall, the results reveal a role for NR in the flowering process.
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PMID:Floral transition and nitric oxide emission during flower development in Arabidopsis thaliana is affected in nitrate reductase-deficient plants. 1854 30

The effects of chitosan (beta-1,4 linked glucosamine, a fungal elicitor), on the patterns of stomatal movement and signaling components were studied. cPTIO (NO scavenger), sodium tungstate (nitrate reductase inhibitor) or L: -NAME (NO synthase inhibitor) restricted the chitosan induced stomatal closure, demonstrating that NO is an essential factor. Similarly, catalase (H(2)O(2) scavenger) or DPI [NAD(P)H oxidase inhibitor] and BAPTA-AM or BAPTA (calcium chelators) prevented chitosan induced stomatal closure, suggesting that reactive oxygen species (ROS) and calcium were involved during such response. Monitoring the NO and ROS production in guard cells by fluorescent probes (DAF-2DA and H(2)DCFDA) indicated that on exposure to chitosan, the levels of NO rose after only 10 min, while those of ROS increased already by 5 min. cPTIO or sodium tungstate or L: -NAME prevented the rise in NO levels but did not restrict the ROS production. In contrast, catalase or DPI restricted the chitosan-induced production of both ROS and NO in guard cells. The calcium chelators, BAPTA-AM or BAPTA, did not have a significant effect on the chitosan induced rise in NO or ROS. We propose that the production of NO is an important signaling component and participates downstream of ROS production. The effects of chitosan strike a marked similarity with those of ABA or MJ on guard cells and indicate the convergence of their signal transduction pathways leading to stomatal closure.
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PMID:Nitric oxide production occurs downstream of reactive oxygen species in guard cells during stomatal closure induced by chitosan in abaxial epidermis of Pisum sativum. 1908 95

THE ROOT EPIDERMIS IS COMPOSED OF TWO CELL TYPES: trichoblasts (or hair cells) and atrichoblasts (or non-hair cells). In lettuce (Lactuca sativa cv. Grand Rapids var. Rapidmor oscura) plants grown hydroponically in water, the root epidermis did not form root hairs. The addition of 10 microM sodium nitroprusside (SNP), a nitric oxide (NO) donor, resulted in almost all rhizodermal cells differentiated into root hairs. Treatment with the synthetic auxin 1-naphthyl acetic acid (NAA) displayed a significant increase of root hair formation (RHF) that was prevented by the specific NO scavenger carboxy-PTIO (cPTIO). In Arabidopsis, two mutants have been shown to be defective in NO production and to display altered phenotypes in which NO is implicated. Arabidopsis nos1 has a mutation in an NO synthase structural gene (NOS1), and the nia1 nia2 double mutant is null for nitrate reductase (NR) activity. We observed that both mutants were affected in their capacity of developing root hairs. Root hair elongation was significantly reduced in nos1 and nia1 nia2 mutants as well as in cPTIO-treated wild type plants. A correlation was found between endogenous NO level in roots detected by the fluorescent probe DAF-FM DA and RHF. In Arabidopsis, as well as in lettuce, cPTIO blocked the NAA-induced root hair elongation. Taken together, these results indicate that: (1) NO is a critical molecule in the process leading to RHF and (2) NO is involved in the auxin-signaling cascade leading to RHF.
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PMID:Nitric oxide functions as a positive regulator of root hair development. 1952 73

We describe an inexpensive and reliable detector for measuring NO emitted in the gas phase from plants. The method relies on the use of a strong oxidizer to convert NO to NO2 and subsequent capture of NO2 by a Griess reagent trap. The set-up approaches the sensitivity for NO comparable to that of instruments based on chemiluminescence and photoacoustic detectors. We demonstrate the utility of our set-up by measuring NO produced by a variety of well established plant sources. NO produced by nitrate reductase (NR) in tobacco leaves and barley aleurone was readily detected, as was the production of NO from nitrite by the incubation medium of barley aleurone. Arabidopsis mutants that overproduce NO or lack NO-synthase (AtNOS1) also displayed the expected NO synthesis phenotype when assayed by our set-up. We could also measure NO production from elicitor-treated suspension cultured cells using this set-up. Further, we have focused on the detection of NO by a widely used fluorescent probe 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM). Our work points to the pitfalls that must be avoided when using DAF-FM to detect the production of NO by plant tissues. In addition to the dramatic effects that pH can have on fluorescence from DAF-FM, the widely used NO scavengers 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) can produce anomalous and unexpected results. Perhaps the most serious drawback of DAF-FM is its ability to bind to dead cells and remain NO-sensitive.
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PMID:Measuring NO production by plant tissues and suspension cultured cells. 1982 39

Chitooligosaccharide (COS) or oligochitosan has been shown to induce tobacco defense responses which are connected with nitric oxide (NO) and OIPK (oligochitosan-induced Ser/Thr protein kinase). The aim of this study was to reveal the relationship between NO production and OIPK pathway in the defense response of tobacco elicited by COS. NO generation was investigated by epidermal strip bioassay and fluorophore microscope using fluorophore diaminofluorescein diacetate (DAF-2DA). Tobacco epidermal cells treated with COS resulted in production of NO, which was first present in chloroplast, then in nucleus, finally in the whole cell; this NO production was sensitive to NO scavenger cPTIO and the mammalian NO synthase (NOS) inhibitor L: -NAME, suggesting that NOS-like enzyme maybe involved in NO generation in tobacco epidermal cells. However, NOS and nitrate reductase (NR, EC 1.6.6.1) inhibitors reduced NO content in tobacco leaves by using NO Assay Kit, suggesting both NOS and NR were involved in NO production in tobacco leaves. Using a pharmacological approach and western blotting, we provide evidence that NO acts upstream of OIPK expression. NO scavenger, NOS inhibitor partly blocked the activation of OIPK and the activities of several defense-related enzymes induced by COS; treatment with NO donor sodium nitroprusside (SNP) induced the activation of OIPK and enhanced the defense systems. The results suggest that COS is able to induce NO generation, which results in up-regulation the activities of some defense-related enzymes through an OIPK-dependent or independent pathway.
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PMID:Nitric oxide production and its functional link with OIPK in tobacco defense response elicited by chitooligosaccharide. 2133 82

The article studies the nitric oxide (NO) levels in the roots of etiolated seedlings of garden peas (Pisum sativum L.) using the DAF-2DA fluorescent probe and fluorescent microscopy. Cross sections of roots of 100-150 microm (the site of a root which is 10-15 mm from the apex) are analyzed. It is shown that the level of NO in the roots after 24 h increased by more than a factor of 2 in the versions with NaNO2 and sodium nitroprusside. At feeding the seedlings with KNO3, a peak in the accumulation of NO in the roots (twofold increase) was observed after 30 min. Fertilizing seedlings with L-arginine (2 mM) increased the intensity of the fluorescence of the root sections by more than a factor of 2. The inoculation of seedlings of rhizobia (Rhizobium leguminosarum by. viceae) contributed to the reduction of NO on the background of the control (H20) and sodium nitroprusside and nitrogen compounds. Scavengers of NO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), hemoglobin) and inhibitors of nitrate reductase and animal NO synthase (sodium tungstate and aminoguanidine hydrochloride) reduced the level of NO in the roots. The results are discussed in relation to the role of NO in plants under the influence of biotic and abiotic factors.
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PMID:[Influence of environmental factors on the generation of nitric oxide in the roots of etiolated pea seedlings]. 2256 91


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