The Molecular Genetics of Higher Plant Nitrate Assimilation

Wray, John L.

doi:10.1007/978-3-7091-6989-6_5

Cited by 34 publications

(28 citation statements)

References 234 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Three steps can be distinguished in this highly regulated pathway: (i) import of nitrate by the cells mediated by a nitrate transporter (NT); (ii) reduction of nitrate to nitrite catalyzed by nitrate reductase (NR); and (iii) reduction of nitrite to ammonium catalyzed by nitrite reductase (NiR) (Caboche and Rouze, 1990;Guerrero et a/., 1981). Eukaryotic NR and NiR have been cloned in a wide variety of organisms, and extensive studies about enzyme structure and gene expression have been carried out (Caboche and Rouze, 1990;Fernandez et a/., 1989a;Wray and Kinghorn, 1989; and references therein). More recently, researchers have turned their attention to the identification of genes for the nitrate transporter and for the regulation of the overall pathway (Crawford and Campbell, 1990).…”

Section: Introductionmentioning

confidence: 99%

Identification of nitrate transporter genes in Chlamydomonas reinhardtii

1994

View full text Add to dashboard Cite

SummaryThe Chlamydomonas reinhardtii nar-2, nar-3, and nar.4 genes, which are within a nitrate-regulated gene cluster containing the nitrate reductase structural gene nit-1, have been related to nitrate transport. Mutant strains defective in nitrate transport and having an active nitrate reductase have been genetically constructed. Their nitrate nonutilizing phenotype has been directly complemented by transformation using the pC0-5 plasmid which carries the nar-2, nar-3, and nar-4 clustered genes. Integration of pC0-5 DNA in the genome of nitrate transport mutants resulted in the expression of these nar transcripts and the recovery of a high affinity nitrate transport activity. Complementation of the nitrate non-utilizing phenotype of the constructed strains was also achieved by co-transformation with plasmids containing nar-2 and nar-3 genes or nar-2 and nar-4, but not with single plasmids containing each individual gene. In addition, DNA sequences of a practically complete cDNA of nar-3 and a partial one of nar-4 have been generated and the deduced amino acid sequences showed a very significant identity with that of the nitrate transporter gene (crnA) from Aspergillus nidulans. These data strongly support the hypothesis that the nitrate transport system in C. reinhardtii contains at least two protein components encoded by the nar-2 and nar-3 genes. The nar-4 gene would produce a protein with a high identity to that of nar-3.

show abstract

Section: Introductionmentioning

confidence: 99%

Identification of nitrate transporter genes in Chlamydomonas reinhardtii

1994

View full text Add to dashboard Cite

show abstract

“…), which reduces the nitrate to nitrite. Nitrate reduction is considered the controlling step in the assimilation of nitrate and has been studied extensively in bacteria, fungi, and higher plants (28). In plants, the enzyme is an homodimer carrying three cofactors, namely FAD, Cyt b557, and the molybdenum cofactor.…”

mentioning

confidence: 99%

Expression of Leaf Nitrate Reductase Genes from Tomato and Tobacco in Relation to Light-Dark Regimes and Nitrate Supply

Galangau

Moureaux²,

Dorbe³

et al. 1988

Plant Physiol.

205

130

View full text Add to dashboard Cite

The influence of light-dark cycles and nitrate supply on nitrate reductase (NR) mRNA levels was studied in two plant species, tobacco (Nicotiana tabacum) and tomato (Lycopersicon esculentum) using specific NR DNA probes. In the same series of experiments, changes in the levels of NR protein (NRP) by enzyme-linked immunosorbent assay and changes in the level of NADH-nitrate reductase activity (NRA) were also followed. During a light-dark cycle, it was found that in both tomato and tobacco, NR mRNA accumulation increased rapidly during the dark period and reached a maximum at the beginning of the day, while NRP reached a peak 2 and 4 hours after mRNA peaked, for tomato and tobacco, respectively. At the end of the day, the amount of mRNA was decreased by a factor of at least 100 compared to sunrise in both species. These results demonstrate that light is involved, although probably not directly, in the regulation of the NR gene expression at the mRNA level. The peak of NRA in tobacco coincided with the peak in NR mRNA accumulation (i.e. sunrise), whereas in tomato the peak of NRA was approximately 5 to 6 hours after sunrise. There is no obvious correlation between NRP and NRA levels during the day. In nitrogen starvation experiments, a rapid decrease of NRP and NRA was detected, while NR mRNA levels were not significantly altered. Upon nitrate replenishment, nitrogen-starved plants accumulated NR mRNA rapidly. These results suggest that the availability of nitrogen affects the expression of NR activity at the transcriptional as well as at the post-transcriptional levels.clones coding for the NR apoprotein (3,4,8) has allowed the study of gene transcription.The influence of light on NRA has been described in a variety of higher plants (for a review see Ref. 10). For many species, extractable NRA rapidly increases when etiolated, nitrate-grown seedlings are placed in white light. By immunological methods, NRA induction has been correlated with de novo synthesis of NRP in barley (21) and maize (17). In this paper, using specific probes for tobacco (3) and tomato (to be published), we show that during a 24 h cycle, the de novo synthesis of NRP during the day follows increases in pools of NR mRNA during the last part of the night.Since the early experiments ofTang and Wu (23) of the apoprotein in response to nitrate was correlated with an increase in the mRNA level. We have studied the levels of NR mRNA, NRP and NRA during nitrate starvation/induction experiments using tobacco and tomato. MATERIALS AND METHODSHigher plants, algae, and some bacteria assimilate nitrogen from their environment primarily by the nitrate reducing pathway. The first step of this route is catalyzed by the enzyme NR' (EC 1.6.6.1.), which reduces the nitrate to nitrite. Nitrate reduction is considered the controlling step in the assimilation of nitrate and has been studied extensively in bacteria, fungi, and higher plants (28). In plants, the enzyme is an homodimer carrying three cofactors, namely FAD, Cyt b557, and the molybdenum cofacto...

show abstract

Section: Introductionmentioning

confidence: 99%

“…Because NR is a substrate (NO3-)- (23). Finally, many chlorate resistant mutants have been isolated and characterized, and most of these mutants have been found to be impaired in nitrate reduction (38).The toxic effects of chlorate have been exploited not only as a means to eliminate plant life but also as a powerful tool to select for mutants with defects in nitrate reduction. Chlorate resistant mutants have been isolated from bacteria, fungi, and plants (21).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Effect of Chlorate Treatment on Nitrate Reductase and Nitrite Reductase Gene Expression in Arabidopsis thaliana

LaBrie¹,

Wilkinson²,

Crawford³

1991

Plant Physiol.

View full text Add to dashboard Cite

The herbicide chlorate has been used extensively to isolate mutants that are defective in nitrate reduction. Chlorate is a substrate for the enzyme nitrate reductase (NR), which reduces chlorate to the toxic chlorite. Because NR is a substrate (NO3-)- (23). Finally, many chlorate resistant mutants have been isolated and characterized, and most of these mutants have been found to be impaired in nitrate reduction (38).The toxic effects of chlorate have been exploited not only as a means to eliminate plant life but also as a powerful tool to select for mutants with defects in nitrate reduction. Chlorate resistant mutants have been isolated from bacteria, fungi, and plants (21). These mutants are usually defective in NR due to lesions in either the NR structural gene or one of the six to seven genes that are required for the synthesis of a MoCo, an essential component of the NR holoenzyme (21). The first plant species that was used to isolate chlorate resistant mutants was Arabidopsis thaliana (4). Dozens of resistant mutants were isolated and found to comprise eight complementation groups (5). We have identified one of these loci, chl3, as the NR structural gene NIA2 (37). Other loci have been shown to be required for MoCo synthesis (e.g. B25) (7). Such mutants have been invaluable for studying the structure, function, and regulation of NR (8,12

show abstract

The Molecular Genetics of Higher Plant Nitrate Assimilation

Cited by 34 publications

References 234 publications

Identification of nitrate transporter genes in Chlamydomonas reinhardtii

Identification of nitrate transporter genes in Chlamydomonas reinhardtii

Expression of Leaf Nitrate Reductase Genes from Tomato and Tobacco in Relation to Light-Dark Regimes and Nitrate Supply

Effect of Chlorate Treatment on Nitrate Reductase and Nitrite Reductase Gene Expression in Arabidopsis thaliana

Contact Info

Product

Resources

About