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  • 1
    Electronic Resource
    Electronic Resource
    LOCAL AND LONG-RANGE SIGNALING PATHWAYS REGULATING PLANT RESPONSES TO NITRATE (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 53 (2002), S. 203-224 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Nitrate is the major source of nitrogen (N) for plants growing in aerobic soils. However, the NO3- ion is also used by plants as a signal to reprogram plant metabolism and to trigger changes in plant architecture. A striking example is the way that a root system can react to a localized source of NO3- by activating the NO3- uptake system and proliferating lateral roots preferentially within the NO3--rich zone. That roots are able to respond autonomously in this fashion implies the existence of local signaling pathways that are sensitive to local changes in the external NO3- concentration. On the other hand, long-range signaling pathways are also needed to modulate these responses according to the plant's N status and to coordinate the allocation of resources between the root and the shoot. This review examines these signaling mechanisms and their interactions with sugar-sensing and hormonal response pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.53.100301.135256
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  • 2
    Electronic Resource
    Electronic Resource
    Cloning and sequence analysis of a cDNA for barley ferredoxin-dependent glutamate synthase and molecular analysis of photorespiratory mutants deficient in the enzyme (1993)
    Springer
    Planta 189 (1993), S. 475-483 
    Details
    ISSN: 1432-2048
    Keywords: Amidotransferase ; Amino-terminal sequences ; Chromosomal assignment ; Glutamate synthase ; Hordeum (mutants) ; Photorespiration mutants (barley) ; Polymerase chain reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The NH2-terminal sequences of ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) purified from barley (Hordeum vulgare L.) and Chlamydomonas reinhardtii (Dangeard), and of a barley peptide, were determined and the barley sequences were used to design oligonucleotide primers for the polymerase chain reaction. A specific 1.3-kilobase (kb) cDNA fragment specifying the NH2-terminal one-third of the mature barley polypeptide, was amplified, cloned and sequenced. The NH2-terminus of plant Fd-GOGAT is highly conserved and homologous to the NH2-terminus of the heavy subunit of Escherichia coli NADPH-GOGAT. Based on sequence homologies, we tentatively identified the NH2-terminal region of Fd-GOGAT as the glutamine-amidotransferase domain, which is related to the corresponding domain of the purF-type amidotransferases. The Fd-GOGAT cDNA clone, and polyclonal antibodies raised against the barley enzyme, were used to analyse four Fd-GOGAT-deficient photorespiratory mutants. Three mutants (RPr 82/1, RPr 82/9 and RPr 84/82) had no detectable Fd-GOGAT protein in leaves, while the fourth (RPr 84/42) had a small amount of cross-reacting material. Hybridization to Northern blots of total leaf RNA revealed that both RPr 82/9 and RPr 84/82 were indistinguishable from the parental line (Maris Mink), having normal amounts of a 5.7-kb mRNA species. On the other hand, RPr 82/2 and RPr 84/42 each contained two distinct hybridizing RNA species, one of which was larger than 5.7 kb, the other smaller. Using a set of wheat-barley telosomic addition lines we have assigned the Fd-GOGAT structural locus to the short arm of chromosome 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198209
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of GmNRT2 expression and nitrate transport activity in roots of soybean (Glycine max) (1998)
    Springer
    Planta 206 (1998), S. 44-52 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Glycine (nitrate transport) ; High-affinity nitrate transporter ; Major facilitator superfamily ; Nitrate induction ; Nutrient uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A full-length cDNA, GmNRT2, encoding a putative high-affinity nitrate transporter was isolated from a Glycine max (L.) root cDNA library and sequenced. The deduced GmNRT2 protein is 530 amino acids in length and contains 12 putative membrane-spanning domains and a long, hydrophilic C-terminal domain. GmNRT2 is related to high-affinity nitrate transporters in the eukaryotes Chlamydomonas reinhardtii and Aspergillus nidulans, and to putative high-affinity nitrate transporters in barley and tobacco. Southern blot analysis indicated that GmNRT2 is part of a small, multigene family in soybean. Expression of GmNRT2 in roots was regulated by the type of nitrogen source provided to plants: GmNRT2 mRNA levels were barely detectable in ammonium-grown plants, higher in nitrogen-deprived plants, and highest in nitrate-grown plants. Induction of GmNRT2 mRNA levels in roots occurred within 1 h after exposure of plants to nitrate. Nitrate induction of GmNRT2 mRNA levels was accompanied by a fourfold increase in net nitrate uptake by soybean roots at 100 μM external nitrate. The molecular and physiological evidence indicates that GmNRT2 is probably a high-affinity nitrate transporter involved in nitrate uptake by soybean roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050372
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of the expression of ferredoxin-glutamate synthase in barley (1997)
    Springer
    Planta 203 (1997), S. 517-525 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Glutamate synthase ; Hordeum (glutamate synthase) ; Light (N assimilation) ; Nitrogen assimilation ; Plant development ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We have investigated the regulation of ferredoxin–glutamate synthase (Fd-GOGAT) in leaves of barley (Hordeum vulgare L. cv. Maris Mink) at the mRNA, protein and enzyme activity levels. Studies of the changes in Fd-GOGAT during plant development showed that the activity in shoots increases rapidly after germination to reach a maximum (on a fresh-weight basis) at day 10 and then declines markedly to less than 50% of the maximal activity by day 30, this decline being correlated with an equivalent loss of Fd-GOGAT protein. Growing the plants in darkness reduced the maximum activity attained in the shoots, but did not affect the overall pattern of the changes or their timing. The activity of Fd-GOGAT increased two- to three-fold within 48 h when etiolated leaves were exposed to light, and Northern blots indicated that the induction occurred at the mRNA level. However, whilst a carbon source could at least partially substitute for light in the induction of nitrate reductase activity, no induction of Fd-GOGAT activity was seen when etiolated leaves were treated with either sucrose or glucose. Interestingly, the levels of Fd-GOGAT mRNA and activity remained high up to a period of 16 h or 72 h darkness, respectively. Compared with plants grown in N-free medium, light-grown plants supplied with nitrate had almost two-fold higher Fd-GOGAT activities and increased Fd-GOGAT mRNA levels, but nitrate had no effect on the abundance of the enzyme or its mRNA in etiolated plants, indicating that light is required for nitrate induction of barley Fd-GOGAT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050221
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  • 5
    Electronic Resource
    Electronic Resource
    The Nir1 locus in barley is tightly linked to the nitrite reductase apoprotein gene Nii (1995)
    Springer
    Molecular genetics and genomics 247 (1995), S. 579-582 
    Details
    ISSN: 1617-4623
    Keywords: Hordeum vulgare L. ; nir1 mutant ; Nitrite reductase apoprotein gene ; RFLP analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract pBNiR1, a cDNA clone encoding part of the barley nitrite reductase apoprotein, was isolated from a barley (cv. Maris Mink) leaf cDNA library using the 1.85 kb insert of the maize nitrite reductase cDNA clone pCIB808 as a heterologous probe. The cDNA insert of pBNiR1 is 503 by in length. The nucleotide coding sequence could be aligned with the 3′ end of other higher plant nitrite reductase apoprotein cDNA sequences but diverges in the 3′ untranslated region. The whole-plant barley mutant STA3999, previously isolated from the cultivar Tweed, accumulates nitrite after nitrate treatment in the light, has very much lowered levels of nitrite reductase activity and lacks detectable nitrite reductase cross-reacting material due to a recessive mutation in a single nuclear gene which we have designated Nir1. STA3999 has the characteristics expected of a nitrite reductase apoprotein gene mutant. Here we have used pB-NiR1 in RFLP analysis to determine whether the mutation carried by STA3999 is linked to the nitrite reductase apoprotein gene locus Nii. An RFLP was identified between the wild-type barley cultivars Tweed (major hybridising band of 11.5 kb) and Golden Promise (major hybridising band of 7.5 kb) when DraI-digested DNA was probed with the insert from the partial barley nitrite reductase cDNA clone, pBNiR1. DraI-digested DNA from the mutant STA3999 also exhibited a major hybridising band of 11.5 kb after hybridisation with the insert from pBNiR1. F1 progeny derived from the cross between the cultivar Golden Promise and the homozygous nir1 mutant STA3999 were heterozygous for these bands as anticipated. Co-segregation of the Tweed RFLP band of 11.5 kb and the mutant phenotype (leaf nitrite accumulation after nitrate treatment/loss of detectable nitrite reductase cross-reacting material at Mr 63000) was scored in an F2 population of 312 plants derived from the cross between the cultivar Golden Promise and the homozygous mutant STA3999. The Tweed RFLP band of 11.5 kb and the mutant phenotype showed strict co-segregation (in approximately one quarter (84) of the 312 F2 plants examined). Only those F2 individuals heterozygous for the RFLP pattern gave rise to F3 progeny which segregated for the mutant phenotype. We conclude that the nir1locus and the nitrite reductase apoprotein gene Nii are very tightly linked.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290349
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  • 6
    Electronic Resource
    Electronic Resource
    Functional analysis of the promoter region of a nodule-enhanced glutamine synthetase gene from Phaseolus vulgaris L. (1992)
    Springer
    Plant molecular biology 19 (1992), S. 837-846 
    Details
    ISSN: 1573-5028
    Keywords: glutamine synthetase ; hairy roots ; nodules ; Phaseolus vulgaris ; protoplasts ; transcriptional regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 5′-flanking region of gln-γ, the nodule-enhanced glutamine synthetase gene from Phaseolus vulgaris L., has been analysed for cis-regulatory elements using a series of 5′ deletions and hybrid gln-γ: : CaMV 35S promoters. The promoters were fused to the uidA reporter gene and their activities tested in two heterologous expression systems. In the first system, the chimaeric genes were transferred to Lotus corniculatus L. using Agrobacterium rhizogenes and their expression was studied in nodulated hairy roots. In the second system, the constructs were electroporated into tobacco mesophyll protoplasts. The results of the 5′ deletion analysis showed that the sequence between −597 and −21 (relative to the ATG codon) was sufficient for nodule-specific expression of the chimaeric gene in nodulated hairy roots, and revealed the existence of at least two positive regulatory elements. Sequences located between −2000 and −597 were able to stimulate expression in nodules but not protoplasts, while the region from −597 to −354 enhanced expression in both nodules and protoplasts. Results obtained with the hybrid gln-γ: :35 S promoters showed that two overlapping restriction fragments (−516/−343 and −474/−293) were able to stimulate expression from a heterologous promoter in an orientation-dependent manner. Previous work has demonstrated the presence of conserved A/T-rich binding sites for nuclear proteins in the region between −516 and −446, and their possible role in regulating gln-γ expression is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027079
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  • 7
    Electronic Resource
    Electronic Resource
    PCR-identification of a Nicotiana plumbaginifolia cDNA homologous to the high-affinity nitrate transporters of the crnA family (1997)
    Springer
    Plant molecular biology 34 (1997), S. 265-274 
    Details
    ISSN: 1573-5028
    Keywords: barley ; Chlamydomonas reinhardtii ; Nicotiana plumbaginifolia ; nitrate transport ; Nrt2 expression ; RT-PCR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A family of high-affinity nitrate transporters has been identified in Aspergillus nidulans and Chlamydomonas reinhardtii, and recently homologues of this family have been cloned from a higher plant (barley). Based on six of the peptide sequences most strongly conserved between the barley and C. reinhardtii polypeptides, a set of degenerate primers was designed to permit amplification of the corresponding genes from other plant species. The utility of these primers was demonstrated by RT-PCR with cDNA made from poly(A)+ RNA from barley, C. reinhardtii and Nicotiana plumbaginifolia. A PCR fragment amplified from N. plumbaginifolia was used as probe to isolate a full-length cDNA clone which encodes a protein, NRT2;1Np, that is closely related to the previously isolated crnA homologue from barley. Genomic Southern blots indicated that there are only 1 or 2 members of the Nrt2 gene family in N. plumbaginifolia. Northern blotting showed that the Nrt2 transcripts are most strongly expressed in roots. The effects of external treatments with different N sources showed that the regulation of the Nrt2 gene(s) is very similar to that reported for nitrate reductase and nitrite reductase genes: their expression was strongly induced by nitrate but was repressed when reduced forms of N were supplied to the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005872816881
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular analysis of barley mutants deficient in chloroplast glutamine synthetase (1990)
    Springer
    Plant molecular biology 14 (1990), S. 297-311 
    Details
    ISSN: 1573-5028
    Keywords: cDNA sequence ; chloroplast protein ; glutamine synthetase ; Hordeum vulgare L. ; mRNA ; mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A barley leaf cDNA library has been screened with two oligonucleotide probes designed to hybridize to conserved sequences in glutamine synthetase (GS) genes from higher plants. Two GS cDNA clones were identified as hybridizing strongly to one or both probes. The larger clone (pcHvGS6) contained a 1.6 kb insert which was shown by primer extension analysis to be an almost full-length cDNA. Both clones were more closely related to cDNAs for the chloroplast form of GS (GS2) from pea and Phaseolus vulgaris than to cDNAs for the cytosolic form (GS1). A sequence identicalto an N-terminal sequence determined from a purified preparation of the mature GS2 polypeptide (NH2-XLGPETTGVIQRMQQ) was found in the pcHvGS6-encoded polypeptide at residues 46–61, indicating a pre-sequence of at least 45 amino acids. The pre-sequence has only limited sequence homology to the pre-sequences of pea and P. vulgaris GS2 subunits, but is similarly rich in basic residues and possesses some of the structural features common to the targeting sequences of other chloroplast proteins. The molecular lesions responsible for the GS2-deficient phenotypes of eight photorespiratory mutants of barley were investigated using a gene-specific probe from pcHvGS6 to assay for GS2 mRNA, and an anti-GS antiserum to assay for GS2 protein. Three classes of mutants were identified: class I, in which absence of cross-reacting material was correlated with low or undetectable levels of GS2 mRNA; class II, which had normal or increased levels of GS2 mRNA but very little GS2 protein; and class III, which had significant amounts of GS2 protein but little or no GS2 activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028767
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  • 9
    Electronic Resource
    Electronic Resource
    Spatially distinct expression of two new cytochrome P450s in leaves of Nepeta racemosa/: identification of a trichome-specific isoform (1997)
    Springer
    Plant molecular biology 33 (1997), S. 875-885 
    Details
    ISSN: 1573-5028
    Keywords: cloning ; cytochrome P450 ; expression ; plant ; trichome ; monoterpenoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a PCR-based approach, two novel cytochrome P450 cDNAs were isolated from a catmint (Nepeta racemosa) leaf cDNA library. The cDNAs (pBSK3C7 and pBSK4C3) were 76.9% identical in their nucleotide sequences, indicating that they are the products of two closely-related genes. A comparison of the sequence of these cDNAs with database sequences indicated that they represent new members of the CYP71 gene family of plant cytochrome P450s. Clone pBSK3C7 contains the full-length coding sequence of a cytochrome P450, whilst pBSK4C3 lacks ca. 6 codons at the 5' end. The cytochromes P450 encoded by these clones were designated CYP71A5 and CYP71A6 (pBSK3C7 and pBSK4C3, respectively). Southern blot analysis indicated that the corresponding genes were present as single copies in the genome of N. racemosa. Northern blot analysis showed that a gene homologous with CYP71A5 was expressed in the related species N. cataria, but no homologue of CYP71A6 was detected in this species. Expression of CYP71A5 in N. racemosa was maximal in flowers, tissues within the apical bud, and young expanded leaves. That of CYP71A6 was maximal in older leaves. Expression of CYP71A5 occurred exclusively in trichomes present on the leaf surfaces, in contrast to that of CYP71A6, which occurred predominantly within the leaf blade tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005706609510
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