Signal storage in phytochrome action on nitrate-mediated induction of nitrate and nitrite reductases in mustard seedling cotyledons

Schuster, C.; Oelmüller, Ralf; Mohr, Hans

doi:10.1007/bf00395077

Cited by 36 publications

(20 citation statements)

References 20 publications

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“…We have previously confirmed with our system (Rajasekhar and Schuster et al 1987) that application of nitrate indeed leads to an induction of NR and NIR in the cotyledons of dark-grown mustard (Sinapis alba L.) seedlings. However, it was also found that this induction can be strongly promoted by light pretreatment -operating through phytochrome -prior to nitrate application.…”

Section: Introductionsupporting

confidence: 64%

Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome

Schuster

Mohr

1990

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Nitrate reductase (NR, EC 1.6.6.1) and nitrite reductase (NIR, EC 1.7.7.1) are the key enzymes of nitrate reduction. It is well established that the appearance of these enzymes is "induced" by nitrate, and it is generally believed that NR is cytosolic while NIR is plastidic. In mustard (Sinapis alba L.) cotyledons we observed two isoforms of NIR (NIR1 and NIR2) using a chromato-focusing technique. Only one of them (NIR2) disappeared when the plastids were damaged by photooxidation in the presence of Norflurazon. It is concluded that NIR2 is plastidic while NIR1 is extraplastidic and not affected by photooxidation of the plastids. Both isoforms appear to have the same molecular weight (60 kilodaltons, kDa). Two distinct translation products which could be immunoprecipitated with NIR antiserum produced against total NIR from mustard were observed which differed slightly in molecular weight (60 versus 63 kDa). The 63-kDa polypeptide was considered to be the precursor of NIR2. While synthesis of NIR protein depended largely on nitrate, the levels of in-vitro-translatable NIR mRNAs were found to be either independent of nitrate and light (NIR1) or controlled by phytochrome only (NIR2). It appears that phytochrome strongly stimulates the level of mRNA while significant enzyme synthesis (NIR2) takes place only in the presence of relatively large amounts of nitrate. Since an increased enzyme level was strictly correlated with an increase of immunoresponsive NIR protein it is improbable that activation of a precursor plays a role. Rather, it is concluded that, in situ, nitrate controls translation.

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Section: Introductionsupporting

confidence: 64%

Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome

Schuster

Mohr

1990

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“…[34] with slight modifications. Twenty organs were pulverized as described above and 3 ml extraction buffer (50 mM Tris-HC1, 3 mM EDTA, 0.5~o (v/v) Tween 80 pH 8.5) was added.…”

Section: Enzyme Assaymentioning

confidence: 99%

Gene expression of nitrite reductase in Scots pine (Pinus sylvestris L.) as affected by light and nitrate

et al. 1994

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A partial cDNA clone (PSnir) encoding the C-terminal region of nitrite reductase was isolated from a lambda gt11 library of the gymnosperm Pimus sylvestris (L.). Nucleotide sequence analysis showed that PSnir contains a reading frame encoding 105 amino acid residues. The amino acid sequence revealed a homology to NiR of 63-68% to dicotyledoneous and of 57-59% to monocotyledoneous species. The protein region implicated to be involved in binding of the prosthetic group is highly conserved between the NiR of the gymnosperm and of angiosperms. In all organs (cotyledonary whorls, hypocotyls, roots) the pattern of NiR gene expression in response to nitrate and light is the same at the level of transcript accumulation and at the enzyme level. This suggests that regulation of NiR gene expression in the Scots pine seedling is predominantly at the level of transcript accumulation. The highest NiR appearance was observed in roots and hypocotyls. In the cotyledonary whorls only small amounts of NiR were found. In roots and hypocotyls the accumulation of NiR mRNA and the appearance of NiR protein is mainly controlled by nitrate, whereas the regulation of NiR gene expression in the whorls is strongly affected by light and the inducive effect of nitrate is only weak.

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“…Crude extracts of tobacco cotyledons were prepared and NIR was assayed according to Schuster et al (1987) with slight modifications.…”

Section: ~Ob = 04)mentioning

confidence: 99%

Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in tobacco

Neininger¹,

Kronenberger²,

Mohr³

1992

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Nitrite reductase (NIR; EC 1.7.7.1) - a key enzyme of nitrate reduction - is known to be induced by nitrate and light. In the present study with tobacco (Nicotiana tabacum L.) seedlings the dependency of NIR gene expression on nitrate, light and a plastidic factor was investigated to establish the nature of the coaction between these controlling factors. A cDNA clone coding for tobacco plastidic NIR was available as a probe. The major results were as follows: (i) The light effect on the appearance of NIR occurred predominantly through phytochrome. However, a specific blue-light effect was also involved. (ii) There was no effect of light on NIR appearance in the absence of nitrate while light exerted a strong effect when nitrate was provided. (iii) Anion-exchange chromatography revealed only a single form of NIR. While experiments involving plastid photooxidation indicated that this NIR is plastidic, a small residual level could not be eliminated by photooxidation. (iv) Northern blot analysis of NIR-transcript levels indicated that a low transcript level existed in the absence of nitrate and light; however, this level appeared to be increased slightly by light (in the absence of nitrate) and by nitrate (in the absence of light). A high transcript level was detected only when light as well as nitrate were provided. A low level was found when the plastids were damaged by photooxidation. It is concluded that plastidic NIR gene expression in tobacco requires positive control by a plastidic factor. Moreover, a synergistic action of phytochrome and nitrate is required to bring about a high transcript level. As found previously with mustard and spinach seedlings, there is no quantitative relationship between the transcript level and the rate of enzyme synthesis.

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Signal storage in phytochrome action on nitrate-mediated induction of nitrate and nitrite reductases in mustard seedling cotyledons

Cited by 36 publications

References 20 publications

Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome

Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome

Gene expression of nitrite reductase in Scots pine (Pinus sylvestris L.) as affected by light and nitrate

Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in tobacco

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