Adaptive Formation of Nitrate Reductase in Rice Seedlings

Tang, Peng; Wu, H. P.

doi:10.1038/1791355a0

Cited by 75 publications

(26 citation statements)

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“…The substitution of tungsten for molybdenum in the NR protein, therefore, induces not only an accumulation of NR apoenzyme, but also that of the corresponding mRNA. (6,13,20,22). Although the diurnal pattern of NR mRNA level was deregulated when tungstate was substituted for molybdate in the culture medium, NR mRNA and protein remained clearly inducible by nitrate.…”

Section: Discussionmentioning

confidence: 95%

Tungstate, a Molybdate Analog Inactivating Nitrate Reductase, Deregulates the Expression of the Nitrate Reductase Structural Gene

Deng¹,

Moureaux²,

Caboche³

1989

Plant Physiol.

139

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Nitrate reductase (NR, EC 1.6.6.1) from higher plants is a homodimeric enzyme carrying a molybdenum cofactor at the catalytic site. Tungsten can be substituted for molybdenum in the cofactor structure, resulting in an inactive enzyme. When nitratefed Nicotiana tabacum plants were grown on a nutrient solution in which tungstate was substituted for molybdate, NR activity in the leaves decreased to a very low level within 24 hours while NR protein accumulated progressively to a level severalfold higher than the control after 6 days. NR mRNA level in molybdategrown plants exhibited a considerable day-night fluctuation. However, when plants were treated with tungstate, NR mRNA level remained very high. NR activity and protein increased over a 24-hour period when nitrate was added back to N-starved molybdate-grown plants. NR mRNA level increased markedly during the first 2 hours and then decreased. In the presence of tungstate, however, the induction of NR activity by nitrate was totally abolished while high levels of NR protein and mRNA were both induced, and the high level of NR mRNA was maintained over a 10-hour period. These results suggest that the substitution of tungsten for molybdenum in NR complex leads to an overexpression of the NR structural gene. Possible mechanisms involved in this deregulation are discussed.In higher plants, the regulation of NR' has been studied extensively under various physiological conditions. A number of factors such as light, mineral nutrition, growth regulators and environmental stress have been shown to affect its activity (21). The precise mechanisms by which these factors modulate NR expression are, at present, not well understood. Molecular tools such as NR monoclonal antibodies (8) and a NR cDNA probe (3) have been obtained in our laboratory to study the regulation of the NR gene expression in tobacco.Higher plant NADH-NR (EC 1.6.6.1) is a nuclear geneencoded homodimer, having a subunit mol wt of 105,000 to 115,000 and containing flavin adenine dinucleotide, hemeFe, and molybdenum cofactor as prosthetic groups (4). Molybdenum is directly implicated in the electron transfer for nitrate reduction. Tungsten, a metal classified with Cr, Mo, and U in the Mendeleieff table, can compete with molybdenum for incorporation into the enzyme complex and results in enzyme inactivation (15,17). In this work, we show that ' Abbreviations: NR, nitrate reductase; rbcS, ribulose bisphosphate carboxylase small subunit. the substitution of tungstate for molybdate in the nutrient solution enhances strongly the expression ofthe NR structural gene. MATERIALS AND METHODS Plant Material and Experimental ConditionsTobacco seeds (Nicotiana tabacum cv Xanthi) were germinated and grown on a sand-peat mixture (1/1, v/v) in the greenhouse. A nitrate and ammonium-containing nutrient solution (10) was applied daily. After 1 month, the seedlings were transferred to a controlled culture room for experimentation under the following conditions: 85% RH, 16 h photoperiod (180 ,umol* m-2 s', fluorescent lam...

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Section: Discussionmentioning

confidence: 95%

Tungstate, a Molybdate Analog Inactivating Nitrate Reductase, Deregulates the Expression of the Nitrate Reductase Structural Gene

Deng¹,

Moureaux²,

Caboche³

1989

Plant Physiol.

139

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“…It is therefore not surprising that NH % + nutrition, as opposed to NO $ − nutrition, has received almost exclusive attention in rice (Bonner, 1946 ;Fried et al, 1965 ;Shen, 1969 ;Wang et al, 1993). However, some reports have indicated that rice does possess some capacity for root NO $ − absorption (Ismunadji & Dijkshoorn, 1971 ;Sasakawa & Yamamoto, 1978 ;Youngdahl et al, 1982 ;Raman et al, 1995) and for the reduction of NO $ − in leaves (Tang & Wu, 1957). Isolated nursery trials have shown that NO $ − pretreatment of rice seedlings can result in enhanced transplanting success (Yamasaki & Seino, 1965), and, perhaps most strikingly, several varieties of Indica rice have been shown to exhibit superior growth on NO $ − under certain conditions (Ta & Ohira, 1981 ;.…”

Section: mentioning

confidence: 99%

Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice: implications for rice cultivation and yield potential

et al. 2000

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Nitrogen limitation compromises the realization of yield potential in cereals more than any other single factor. In rice, the world's most important crop species, the assumption has long been that only ammonium-N is efficiently utilized. Consequently, nitrate utilization has been largely ignored, although fragmentary data have suggested that growth could be substantial on nitrate. Using the short-lived radiotracer "$N, we here provide direct comparisons of root transmembrane fluxes and cytoplasmic pool sizes for nitrate-and ammonium-N in a major variety of Indica rice (Oryza sativa), and show that nitrate acquisition is not only of high capacity and efficiency but is superior to that of ammonium. We believe our results have implications for rice breeding and molecular genetics as well as the design of water-management and fertilization regimes. Potential strategies to harness this hitherto unexplored N-utilization potential are proposed.

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“…With rare exceptions (Streit et al, 1986), NR genes of bacteria, fungi, and higher plants a11 respond to nitrate induction (Kleihofs and Wamer, 1990). This very characteristic of substrate inducibility of a plant enzyme has fascinated many plant physiologists ever since the discovery of the phenomenon (Tang and Wu, 1957). It is alluring to contemplate why this trait has been conserved during evolution while NR genes of higher plants have acquired additional effective means of regulation.…”

Section: Rp07035-25 and Gm46116 Jb Was Supported By Nih Geneticsmentioning

confidence: 99%

5[prime] Proximal Regions of Arabidopsis Nitrate Reductase Genes Direct Nitrate-Induced Transcription in Transgenic Tobacco

et al. 1994

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Nitrate redudase (NR) is the first enzyme in nitrate assimilation, a critica1 process for plant survival. l h e regulation of NR gene expression is complex, involving both interna1 and externa1 factors. O f these, nitrate indudion of NR gene expression has been studied most extensively and is well conserved among baderia, fungi, and higher plants. We are interested in understanding the mechanism of nitrate indudion of higher plant NR genes. Here we describe promoter analyses of the 5' flanking regions of the Arabidopsis NR genes, NR1 and NRZ, with resped to nitrate indudion of gene expression. To facilitate these analyses, a nitrate indudion procedure using 1, transgenic tobacco plants was established. Approximately 1.5-kb 5' flanking regions of the two Arabidopsis NR genes (NR1 and NRZ) were fused to a reporter gene and its expression in transgenic plants was analyzed. Deletion analyses of these regions show that 238-and 188-bp 5' flanking regions of the NR1 and NRZ, respedively, contain sequences responsive to nitrate indudion.

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Adaptive Formation of Nitrate Reductase in Rice Seedlings

Cited by 75 publications

References 4 publications

Tungstate, a Molybdate Analog Inactivating Nitrate Reductase, Deregulates the Expression of the Nitrate Reductase Structural Gene

Tungstate, a Molybdate Analog Inactivating Nitrate Reductase, Deregulates the Expression of the Nitrate Reductase Structural Gene

Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice: implications for rice cultivation and yield potential

5[prime] Proximal Regions of Arabidopsis Nitrate Reductase Genes Direct Nitrate-Induced Transcription in Transgenic Tobacco

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