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  • 36.40.+d  (210)
  • gene expression  (195)
  • Industrial Chemistry
  • Inorganic Chemistry
  • Seismology
  • Springer  (412)
  • Ocean Drilling Program, Texas A&M University, College Station, Eds.: K. Tamaki, J.C. Ingle Jr, et al.  (2)
  • 1990-1994  (412)
  • 1950-1954  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 50 (1994), S. 958-962 
    ISSN: 1420-9071
    Keywords: Plasminogen activator ; active oxygen ; gene expression ; radical scavengers ; endothelial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Active oxygen, produced by cultured cells following stimulation with various growth factors, seems to be involved in signal transduction leading to cellular responses such as gene expression and growth modulation. In the present study, the intracellular oxidation state was measured in immortalized human endothelial cells (ECV304) after treatment with tumor necrosis factor (TNF)α, using a fluorescent dye and a laser-scanning confocal microscope. The intracellular oxidation state was increased 60 min after the addition of TNFα, and this increase was abolished by a radical scavenger, N-acetylcysteine (NAC), which is also a precursor of glutathione, and by pyrrolidine dithiocarbamate (PDTC). TNFα increased the steady state level of urokinase-type plasminogen activator (uPA), and NAC inhibited this increase at a dose that also inhibited the increase in the intracellular oxidation state. PDTC, on the other hand, did not affect the induction of the uPA gene by TNFα. These results suggest that intracellular glutathione level rather than the oxidation state is necessary for the induction of the uPA gene by TNFα.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 58 (1994), S. 57-62 
    ISSN: 1432-0649
    Keywords: 32.80.Pj ; 42.50.Vk ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mechanism responsible for transitions of laser-cooled trapped ions from an ordered “crystal” state to an irregular “cloud” state has been discussed controversially. A numeric and analytic study of the relative motion of two trapped ions without laser cooling is performed and compared with the results of previous simulations involving the laser. It turns out that the system without laser, in spite of its simplicity, already exhibits a non-monotonic dependence of crystal stability on trap parameters, which is linked to the presence of low-order nonlinear resonances.
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  • 3
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The involvement of a hypocalcemic hormone calcitonin (CT) in the expression of hepatic Ca2+-binding protein regucalcin mRNA was investigated. The change of regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin complementary DNA (0.9 kb). A single oral administration of calcium chloride (100 mg Ca/100 g body weight) to rats induced a remarkable increase in the serum calcium concentration and a corresponding elevation of the liver calcium content during 120 min after the administration. Thyroparathyroidectomy (TPTX) did not cause a significant increase in the liver calcium content after calcium administration. Hepatic regucalcin mRNA level was markedly elevated by calcium administration; the level was about 180% of controls at 60 min after the administration. This increase was completely abolished by TPTX. A single subcutaneous administration of CT (synthetic eel CT; 25–100 MRC mU/100 g) to TPTX rats received oral administration of calcium (100 mg/100 g) produced a remarkable increase in hepatic regucalcin mRNA levels; the level was about 280% of controls with the dose of 25 MRC mU CT/100 g. The present finding suggests that the expression of hepatic mRNA is stimulated by CT, and that the hormonal effect is mediated through Ca2+ in rat liver.
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  • 4
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; phenobarbital ; rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of phenobarbital on the expression of calcium-binding protein regucalcin mRNA in rat liver was investigated. The change of regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin cDNA (0.9 kb of open reading frame). Phenobarbital (4, 8 and 12 mg/ 100 g body weight) was intraperitoneally administered to rats 3 times with 24 h intervals, and the animals were sacrificed by bleeding at 24 h after the last administration. The hepatic regucalcin mRNA levels were markedly reduced by phenobarbital administration. This decrease was about 50% of control level with the 12 mg/100 g dose. Moreover, the hepatic regucalcin concentration was significantly decreased by the administration of phenobarbital (12 mg/100 g), although the serum regucalcin concentration was not altered appreciably. Meanwhile, serum transaminases (GOT and GPT) activities were not increased by the administration of phenobarbital (4 and 12 mg/100 g). The present study demonstrates that the expression of hepatic regucalcin mRNA is decreased by phenobarbital administration in rats, suggesting that regucalcin does not have a role in drug metabolism related to phenobarbital.
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  • 5
    ISSN: 1573-4919
    Keywords: pressure overload ; myocardium ; gene expression ; fibroblast ; extracellular matrix ; ventricular hypertrophy ; growth factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Transforming Growth Factor-beta1 (TGF-β1) is expressed in the heart by muscle and non-muscle cardiac cells.In vitro, cardiac myocytes and non-muscle cells including cardiac fibroblasts and endothelial cells respond to regulatory effects of TGF-β1. Expression of TGF-β1 in the heart is subject to regulation by hemodynamic stimuli. Increased expression of mRNA transcripts for TGF-β1 has been reported in several models of cardiac hypertrophy. The objective of this study was to determine the effect of TGF-β1 in the myocardium. TGF-β1 was injected intravenously. Expression of mRNA transcripts for functional and structural proteins was determined by Northern hybridization analysis. DNA synthesis was determined by measurement of3H-thymidine incorporation into ventricular DNA. The results showed differential regulation of mRNAs for myocyte- and non-myocyte-specific proteins in the heart of TGF-β1 treated rats. Moderate but statistically significant decrease in DNA synthesis was observed in the heart of TGF-β1 treated rats (37.5%, P〈0.025). Together, these data point to a physiological role for TGF-β1 in the heart. They further suggest that similar to its diversein vitro cell-specific regulatory effects, TGF-β1 may have multicellular targets in the heart. Effect of TGF-β1 alone or combined with those of other cytokines/hormones that come into play, as the result of its administration, may be responsible for altered gene expression and DNA synthesis in the myocardium. We propose that in experimental models of myocardial hypertrophy which are associated with increased expression of TGF-β1 in the heart, the contribution of regulatory effects of this growth factor to the manifestations of ventricular hypertrophy could be significant.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 135 (1994), S. 79-88 
    ISSN: 1573-4919
    Keywords: calcium ; nucleus ; calpain ; calmodulin ; cell division ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Calcium has long been known to play a role as a key cytoplasmic second messenger, but until relatively recently its possible involvement in nuclear signal transduction and the regulation of nuclear events has not been extensively studied. Evidence revealing the presence of transmembrane nuclear Ca2+ gradients and a variety of intranuclear Ca2+ binding proteins has fueled renewed interest in this key ion and its involvement in cell-cycle timing and division, gene expression, and protein activation. This review will offer an overview of the current state of knowledge and theory regarding calcium orchestration of nuclear functions and events and discuss possible future directions in this field of study.
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  • 7
    ISSN: 1573-4919
    Keywords: poly(ADP-ribosyl) transferase (human) ; autoregulation ; gene expression ; promoter structure ; cruciform structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Human nuclear poly(ADP-ribosyl)transferase (ADPRT) modifies proteins with branched ADP-ribose-polymers. Various proteins, including ADPRT itself, serve as acceptors for polyADP-ribose. Target proteins include those controlling basic cellular processes such as DNA repair, differentiation and proliferation. Because of the outstanding features of this enzyme: automodification, several functional domains and central role in physiology of the cell, the molecular biology of ADPRT gained wide interest. The promoter structure contains several CCAAT/TATA boxes and SP1 sites. However, there is no CCAAT/TATA box in the neighbourhood of an SP1 site and, thus no obvious site for initiation of transcription. Within this region there are several noteworthy inverted repeats, which by internal basepairing could form two types of cruciform structures. Deletion analysis revealed that these cruciform structures have functional significance. Removal of one type increases the promoter activity, whereas removal of the other diminishes the promoter function. Overexpression of ADPRT from heterologous promoters (MMTV, SV40) leads to repression of the activity of the ADPRT promoter. Indeed, ADPRT was shown to bind specifically to one type of cruciform structure. This specific interaction indicates autorepression of the ADPRT gene: the enzyme ADPRT acts directly as a negative modulator of the activity of its own promoter.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 133-134 (1994), S. 235-243 
    ISSN: 1573-4919
    Keywords: creatine kinase ; mitochondria ; metabolism ; creatine phosphate shuttle ; gene expression ; muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Mitochondrial Creatine Kinase (MtCK) is responsible for the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine, and exists in mammals as two isoenzymes encoded by separate genes. In rats and humans, sarcomere-specific MtCK (sMtCK) is expressed only in skeletal and heart muscle, and has 87% nucleotide identity across the 1257 bp coding region. The ubiquitous isoenzyme of MtCK (uMtCK) is expressed in many tissues with highest levels in brain, gut, and kidney, and has 92% nucleotide identity between the 1254 bp coding regions of rat and human. Both genes are highly regulated developmentally in a tissue-specific manner. There is virtually no expression of sMtCK mRNA prior to birth. Unlike cytosolic muscle CK (MCK) and brain CK (BCK), there is no developmental isoenzyme switch between the MtCKs. Cell culture models representing the tissue-specific expression of either sMtCK or uMtCK are available, but there are no adequate developmental models to examine their regulation. Several animal models are available to examine the coordinate regulation of the CK gene family and include 1) Cardiac Stress by coarctation (sMtCK, BCK, and MCK), 2) Uterus and placenta during pregnancy (uMtCK and BCK), and 3) Diabetes and mitochondrial myopathy (sMtCK, BCK, and MCK). We report the details of these findings, and discuss the coordinate regulation of the genes necessary for high-energy transduction.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 135 (1994), S. 89-98 
    ISSN: 1573-4919
    Keywords: calcium ; cell death ; nuclei ; apoptosis ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The last decade has seen the rapid development of research investigating the molecular mechanisms whereby hormones, peptide growth factors and cytokines regulate cell metabolism, differentiation and proliferation. One general signalling mechanism used to transfer the information delivered by agonists into appropriate intracellular compartments involves the rapid Ca2+ redistribution throughout the cell, which results in transient elevations of the cytosolic free Ca2+ concentration. Ca2+ signals are required for a number of cellular processes including the activation of nuclear processes such as gene transcription and cell cycle events. The latter require that appropriate Ca2+ signals elicited in response to agonists be transduced across the nuclear envelope. It has generally been assumed that small molecules, metabolites and ions could freely diffuse across the nuclear envelope. Nevertheless several findings during the past few years have suggested that nuclear pore permeability can be regulated and that ion transport systems and ion-selective channels may exist on the nuclear membranes and regulate intranuclear processes. Intranuclear Ca2+ fluctuations can affect chromatin organization, induce gene expression and also activate cleavage of nuclear DNA by nucleases during programmed cell death or apoptosis. The possible mechanisms involved in nuclear Ca2+ transport and the control of nuclear Ca2+-dependent enzymes in apoptosis is discussed below.
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  • 10
    ISSN: 1573-4978
    Keywords: retinoic acid ; skin ; differential hybridization ; cloning ; keratinocytes ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A retinoic acid (RA) inducible skin-specific gene transcript (RIS-1) was isolated by differential hybridization screening of a RA-treated human skin cDNA library. The library was constructed from pooled RNA derived from normal adult human skin treated with alltrans-RA for 4 h (n=6) and 12 h (n=6)in vivo. RIS-1 cDNA corresponded to a 0.6 kb transcript that was barely detectable in normal adult human skin but was significantly induced by 8 h in RA-treated compared to vehicle-treated skin (range 1.1–3.6 fold). Prolonged RA treatment for up to 24 h further increased relative RIS-1 mRNA levels by 1.3–5.5 fold. HPLC analysis of the RA content of 0.1% RA-treated skinin vivo revealed significant levels at 6 h (18.8–120.6 ng RA/g wet weight tissue; approximately 240 nM), immediately preceding the time point at which the increased RIS-1 mRNA level was first seen. This concentration of RA also induced the mRNA levels for cellular RA binding protein II (1.6–19 fold), a marker of RA activity in human skin. RIS-1 mRNA was detected by Northern and dot blotting only in normal skin but not in any other normal human tissues examined, indicating a tissue-specific pattern of gene expression. RIS-1 transcripts were detected at very low levels in untreated cultured human epidermal keratinocytes, while no expression was seen in dermal fibroblasts and melanocytes, the other major cell types in skin. Southern analysis of human and mouse DNA indicated the existence of evolutionarily conserved sequences for RIS-1 between these two species. The polypeptide sequence derived from the partial RIS-1 cDNA was found to be identical to the calcium binding domain found in ‘psoriasin’, a gene whose expression appears to be increased in the skin of psoriasis patients.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 24 (1994), S. 185-194 
    ISSN: 1573-5028
    Keywords: gene expression ; light/nitrate regulation ; nitrate reductase ; nitrate transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mRNA accumulation pattern of the Chlamydomonas reinhardtii nitrate assimilation-related gene cluster has been elucidated. In ammonium-grown wild-type cells, nit-1 (nitrate reductase, NR), nar-1, nar-2 and nar-3 (nitrate transporter) genes showed very similar kinetics of expression when transferred to nitrate medium. Transcripts of all these genes accumulated transiently in ammonium-grown wild-type cells after a one-hour incubation in nitrogen-free medium, and practically disappeared at about 2 hours. Mutant strains lacking functional nitrate reductase showed similar accumulation kinetics of these transcripts during both nitrate induction and derepression in nitrogen-free media. In contrast to the other nar transcripts, that nar-4, a gene sharing similar sequences with nar-3, accumulated in small amounts in wild-type cells, and only increased after a long nitrate induction period. Nitrate and light showed a strong positive effect on the accumulation of nit-1 gene transcripts. Acetate as a carbon source allowed accumulation of nit-1 mRNA in the dark, indicating the existence of interactions between light and carbon metabolism in nit-1 gene expression. Our data strongly suggest that NR negatively autoregulates its own expression and that of nar genes.
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  • 12
    ISSN: 1573-5028
    Keywords: plant transformation ; chaperonin 60β ; β-glucuronidase ; wound repression ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the pattern of gene regulation of the plastid chaperonin 60β gene family a chimaeric gene was constructed fusing the 5′-flanking region of the chaperonin 60β B3 gene to the β-glucuronidase reporter gene. Histochemical and fluorometric analysis of the GUS activity present in transgenic plants harbouring this gene construct showed that the B3 promoter is expressed in leaves, stem, petioles and several flower tissues. The pattern of cell type-specific expression in stems and flowers was found to be developmentally regulated. Expression of the B3 promoter was found not to be heat-inducible, but highly repressed by wounding. The rapid decay in GUS activity upon wounding indicates that, at least under some physiological conditions, the gene product of this reporter gene is not as stable as has been previously thought.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 24 (1994), S. 879-888 
    ISSN: 1573-5028
    Keywords: barley ; cold acclimation ; gene expression ; low temperature genes ; nuclear run-on transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several low-temperature-responsive (LTR) genes from barley have been shown to have high steady-state transcript levels. Run-on transcription was used to determine the control of expression of these LTR genes. Six of these are shown to be transcriptionally regulated (blt 4/9, blt 101, blt 1015, blt 63, blt 49, blt 410) whilst three are post-transcriptionally regulated (blt 14, blt 411, blt 801). Two transcriptionally regulated genes (blt 4/9 and blt 101) and one post-transcriptionally regulated gene (blt 14) have been used in expression studies. The time course for the appearance and decay of these transcripts is given. Initial appearance and steady-state levels of individual transcripts have different temperature characteristics but no single gene correlates with the cold acclimation response. We suggest that these different response profiles may represent a means of fine-tuning the low-temperature response. One gene, blt 4/9, also accumulated high steady-state levels of transcript in response to drought and a nutrient stress. However, only drought has an acclimating effect on barley plants.
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  • 14
    ISSN: 1573-5028
    Keywords: Spinacia oleracea ; chemical cleavage ; gene expression ; polymerase chain reaction ; protein transport ; SDS-PAGE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 24 kDa outer envelope membrane protein of spinach chloroplasts (omp24) represents a major constituent of this membrane. Sequences of tryptic and endoprotease Glu-C peptides derived from omp24 allowed the design of oligonucleotides which were used to generate a DNA fragment by polymerase chain reaction using spinach cDNA as template. This fragment served as a probe to screen a cDNA library for a full-length clone of the omp24 coding sequence. The protein predicted from the complete sequence only has 148 amino acids and a molecular mass of 16294 Da. It is an acidic protein (calculated isoelectric point 4.8) with a high content of proline residues. Expression of the coding sequence in Escherichia coli and characterization of the purified recombinant protein produced revealed that the overestimation of its molecular mass by SDS-PAGE (ca. 25 kDa) is due to its abnormal amino acid composition. Despite its rather low hydrophobicity (polarity index 49%), omp24 appears to be deeply embedded in the outer membrane. Insertion of omp24 into the membrane proceeds almost independently of surface receptors or targeting sequence but, in contrast to other known outer envelope membrane proteins, is stimulated by ATP.
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  • 15
    ISSN: 1573-5028
    Keywords: gene expression ; light ; nitrate ; nitrite reductase ; Pimus sylvestris L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A partial cDNA clone (PSnir) encoding the C-terminal region of nitrite reductase was isolated from a λgt 11 library of the gymnospermPimus 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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  • 16
    ISSN: 1573-5028
    Keywords: castor bean (Ricinus communis) ; catalase gene ; gene expression ; germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two catalase genes,cat1 andcat2, have been isolated from the castor bean genome. They were located in the same direction on a chromosome at a distance of 2.4 kb,cat1 being on the downstream side ofcat2. The two genes contained introns at the same positions except that one of the 7 introns incat1 is missing incat2 and the corresponding introns differed in size and sequence between the two genes. The translated regions of the two genes had the same number of nucleotides and exhibited 81.3% nucleotide sequence identity. In addition to introns, the nucleotide sequences of the 5′-and 3′-flanking regions are highly divergent between the two genes. In etiolated seedlings,cat1 mRNA was present abundantly in endosperms and cotyledons and only in a small amount in roots. Thecat1 mRNA could not be detected in hypocotyls. By contrast,cat2 mRNA is most abundant in hypocotyls and roots, while endosperms and cotyledons contained only low levels ofcat2 mRNA. Although neithercat1 norcat2 mRNA could be detected in dry seeds, both mRNAs showed temporal accumulation in the endosperm in response to germination. These results suggest that expression of two tightly linked catalase genes of castor bean,cat1 andcat2, are differentially regulated during development.
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  • 17
    ISSN: 1573-5028
    Keywords: β-tubulin ; microtubules ; maize ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four different β-tubulin coding sequences were isolated from a cDNA library prepared from RNA from maize seedling shoots. The four genes (designated tub4, tub6, tub7 and tub8) represented by these cDNA clones together with the tub1 and tub2 genes reported previously encode six β-tubulin isotypes with 90–97.5% amino acid sequence identity. Results from phylogenetic analysis of 17 β-tubulin genes from monocot and dicot plant species indicated that multiple extant lines of β-tubulin genes diverged from a single precursor after the appearance of the two major subfamilies of α-tubulin genes described previously. Hybridization probes from the 3′ non-coding regions of six β-tubulin clones were used to quantify the levels of corresponding tubulin transcripts in different maize tissues including developing anthers and pollen. The results from these dot blot hybridization experiments showed that all of the β-tubulin genes were expressed in most tissues examined, although each gene showed a unique pattern of differential transcript accumulation. The tub1 gene showed a high level of transcript accumulation in meristematic tissues and almost no accumulation in the late stages of anther development and in pollen. In contrast, the level of tub4 transcripts was very low during early stages of male flower development but increased markedly (more than 100 times) during the development of anthers and in pollen. Results from RNAse protection assays showed that this increased hybridization signal resulted from expression of transcripts from one or two genes closely related to tub4. The tub4-related transcripts were not present in shoot tissue. Transcripts from the tub2 gene accumulated to very low levels in all tissues examined, but reached the highest levels in young anthers containing microspore mother cells. RNAse protection assays were used to measure the absolute levels of α- and β-tubulin transcripts in seedling shoot and in pollen. The α-tubulin gene subfamily I genes (tua1, tua2, tua4) contributed the great majority of α-tubulin transcripts in both shoot and pollen. Transcripts from the β-tubulin genes tub4, tub6, tub7, and tub8 were predominant in shoot, but were much less significant than the tub4-related transcripts in pollen.
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  • 18
    ISSN: 1573-5028
    Keywords: gene expression ; b-ZIP motif ; seed storage proteins ; trans-acting factors ; transcription factors ; transcriptional regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Opaque-2 (O2) gene from maize encodes a transcriptional activator of the b-ZIP class. We have isolated and characterized a gene from sorghum, related in sequence to the O2 gene from maize. A single copy of the gene is present in sorghum. Both genomic and cDNA sequences of the O2-related sorghum gene were determined. The sequence is highly homologous to maize O2 both in the promoter and in the coding region. The most closely related sequences contain the b-ZIP domain with only 11 amino acid substitutions in a total of 122 residues. In transient expression assays, the sorghum O2-related coding sequence, expressed from a CaMV 35S promoter, activates expression from the maize b-32 promoter as effectively as that obtained with the maize O2 sequence.
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  • 19
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; dwarf mutant ; gene expression ; gibberellin ; subtractive hybridization ; tonoplast intrinsic protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Arabidopsis ga1 mutant has very low levels of endogenous, active gibberellins and thus has an extreme dwarf phenotype; application of GA3 induces stem elongation and flower development. To test the hypothesis that GA action in this system involves changes in gene expression, we have cloned mRNAs whose abundance changes following GA application. A subtraction cloning scheme for the isolation of differentially regulated cDNAs was established, involving hybridization of single-stranded cDNA to biotinylated mRNA. cDNA populations enriched up to 150-fold in GA-regulated sequences were produced and cDNA libraries generated. Screening of these libraries has isolated two clones that identify mRNAs of ca. 1100 and 750 bases whose abundance is markedly increased 24 h after GA application. One of these clones encodes the vegetative form of the Arabidopsis tonoplast intrinsic protein (γ-TIP), a water channel protein, the expression of which has recently been shown to be correlated with regions of cell expansion. The second clone is expressed only in the inflorescence and encodes a proline- and glycine-rich protein that may be a cell wall component.
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  • 20
    ISSN: 1573-5028
    Keywords: Cucumis melo ; melon ; phenylalanine ammonia-lyase ; gene expression ; ripening ; wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phenylalanine ammonia-lyase (PAL) is the first enzyme of phenylpropanoid biosynthesis involved in the synthesis of a multiplicity of plant natural products. We have isolated and characterized a nearly fulllength cDNA clone (pmPAL-1) corresponding to a melon fruit (Cucumis melo L. var. reticulatus) gene coding for a protein which is highly similar to PAL from other lants. Melon fruit PAL is transcriptionally induced both in response to fruit ripening and wounding. PAL gene expression follows the kinetics of expression of the ethylene biosynthetic genes during fruit development. In contrast, ethylene biosynthetic genes show different induction kinetics compared to PAL expression in response to wounding. Similar results have been found for two other genes coding for enzymes involved in flavonoid biosynthesis (chalcone synthase, CHS; chalcone isomerase, CHI). Our results imply that regulation of defense gene expression in melon is a co-ordinated process in response to both ethylene and an ethylene-independent wound signal.
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  • 21
    ISSN: 1573-5028
    Keywords: Arabidopsis ; embryo ; gene expression ; oleosin ; promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Progressive deletions of the 5′-flanking sequences of an Arabidopsis oleosin gene were fused to β-glucuronidase (GUS) and introduced into Brassica napus plants using Agrobacterium-mediated transformation. The effect of these deletions on the quantitative level of gene expression, organ specificity and developmental regulation was assessed. In addition, the influence of abscisic acid (ABA), jasmonic acid (JA), sorbitol and a combined ABA/sorbitol treatment on gene expression was investigated. Sequences that positively regulate quantitative levels of gene expression are present between −1100 to −600 and −400 to −200 of the promoter. In addition, sequences present between −600 and −400 down-regulate quantitative levels of expression. In transgenic B. napus plants, the oleosin promoter directs seed-specific expression of GUS which is present at early stages of seed development and increases throughout seed maturation. Sequences present between −2500 and −1100 of the promoter are involved in modulating the levels of expression at early stages of embryo development. Histochemical staining of embryos demonstrated that expression is uniform throughout the tissues of the embryo. Sequences involved in the response to ABA and sorbitol are present between −400 and −200. The induction of GUS activity by a combined ABA/sorbitol treatment is additive suggesting that ABA is not the sole mediator of osmotically induced oleosin gene expression. A response to JA was only observed when the oleosin promoter was truncated to −600 suggesting that the reported effect of JA on oleosin gene expression may be at a post-transcriptional level.
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  • 22
    ISSN: 1573-5028
    Keywords: abscisic acid ; Arabidopsis thaliana ; gene expression ; mutants ; signal transduction ; stress ; thiol protease ; wilting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sequence and expression characteristics are described of a wilt-inducible gene in Arabidopsis thaliana. A 1494 encodes a potential thiol protease whose mRNA accumulates rapidly in shoot tissue upon the loss of turgor. A1494 mRNA levels peaked after ca. 4 h and declined thereafter. Dehydration also induced rapid biosynthesis of the phytohormone abscisic acid (ABA), which continued for at least 9 h. Exogenous ABA induced the accumulation of A1494 mRNA, with kinetics similar to those after wilting. Rehydration of wilted shoots led to a rapid decline in the content of both ABA and A1494 mRNA. Wilting and ABA independently induced A1494 expression as evidenced by the effects of ABA and wilting on the ABA-deficient aba-1 and ABA-insensitive abi-1 and abi-3 genotypes. A1494 mRNA was not detectable in aba-1 shoots but accumulated rapidly after either wilting or ABA treatment, whereas the shoot ABA content was increased only by ABA treatment. ABA had no effect on A1494 mRNA levels in the abi-1 and abi-3 mutants but wilting did result in enhanced A1494 expression. Heat shock had only a minor effect on A1494 mRNA levels, whereas exposure to low temperature resulted in substantial accumulation of A1494 mRNA in wild-type shoots. However, this latter response, unlike that to drought, was mediated exclusively via ABA synthesis as demonstrated by the lack of A1494 mRNA accumulation in cold-treated aba-1 shoots.
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  • 23
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    Plant molecular biology 25 (1994), S. 369-376 
    ISSN: 1573-5028
    Keywords: ATP synthase ; chloroplast ; gene expression ; plastid ; RNA stability ; transcription
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    Topics: Biology
    Notes: Abstract Plastids present in different tissues may vary morphologically and functionally, despite the fact that all plastids within the same plant contain identical genomes. This is achieved by regulation of expression of the plastid genome by tissue-specific factors, the mechanisms of which are not fully understood. The proton translocating ATP synthase/ATPase is a multisubunit complex composed of nine subunits, six encoded in the plastid and three in the nucleus. We have investigated the tissue-specific expression of the large ATP synthase gene cluster in spinach (Spinacia oleracea). This gene cluster encodes four of the six plastid-encoded ATP synthase genes. Transcript abundance, transcriptional activity, and transcript stability were investigated relative to gene dosage in root plastids and in stem, leaf, and flower chloroplasts. All three of these factors display significant tissue-specific variation. It was intriguing to discover that, although transcript abundance normalized to gene dosage varies in each tissue, transcript abundance as a proportion of the entire plastid RNA population in each tissue is not significantly different. Thus it appears that in these tissues the variation in transcription and stability of transcripts derived from the large ATP synthase gene cluster balances to yield an equivalent proportion of these transcripts in the plastid RNA population. Expression of this gene cluster in photosynthetic as well as non-photosynthetic tissues may facilitate the plasticity of structure and function which is characteristic of plastids.
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  • 24
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    Plant molecular biology 26 (1994), S. 85-93 
    ISSN: 1573-5028
    Keywords: gene expression ; monocot cells ; promoter strength ; transient expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An upstream region isolated from a eukaryotic algal virus adenine methyltransferase gene was tested for promoter function in plants. Fusion of this region to the chloramphenicol acetyltransferase reporter gene resulted in significantly higher expression than fusion with the cauliflower mosaic virus 35S promoter. Strong levels of expression were also found in electroporated monocot plant cells. The promoter activity in transgenic tobacco plants showed tissue-specific expression. Leaves had the highest expression followed by stems and flowers. The promoter activity was not detected in root tissue. Environmental cues, such as light, and the phytohormones auxin and cytokinines had no effect on the promoter's expression. This promoter might be utilized to achieve high levels of expression of introduced genes in higher plants.
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  • 25
    ISSN: 1573-5028
    Keywords: cell cycle ; gene expression ; meristem ; promoter analysis ; transgenic Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A genomic clone for the cyc07 gene, which is expressed specifically at the S phase during the cell cycle in synchronous cultures of periwinkle (Catharanthus roseus) cells, was isolated. Determination of the nucleotide sequence of the clone revealed that the cyc07 gene consists of seven exons separated by six introns. Genomic Southern analysis indicated that the cyc07 gene is present as a single copy per haploid genome in periwinkle. Expression of related genes was detected in a wide range of other plants. Transgenic Arabidopsis plants were generated that expressed the gene for β-glucuronidase (GUS) under the control of the promoter of the cyc07 gene. The tissue-specific pattern of expression directed by the promoter was investigated by analysis of GUS activity. Histochemical tests demonstrated that 589 bp of the 5′-upstream sequence of the cyc07 gene could direct specifical expression of the GUS reporter gene in meristematic tissues in transgenic plants. The spatial pattern of expression directed by the promoter was closely correlated with meristematic activity and cell proliferation, suggesting an association between the function of the cyc07 gene and cell proliferation.
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  • 26
    ISSN: 1573-5028
    Keywords: gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter
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    Topics: Biology
    Notes: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
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  • 27
    ISSN: 1573-5028
    Keywords: gene expression ; RNA stability regulation ; chloroplast RNA-binding protein (cRBP) ; environmental stress ; Mesembryanthemum crystallinum
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    Topics: Biology
    Notes: Abstract We report the characterization of transcripts from the halophyte, Mesembryanthemum crystallinum, encoding a protein with high homology to chloroplast RNA-binding proteins (cRBP). In this plant chloroplast-related functions are largely protected against salt stress. cRBP transcripts are derived from a single gene, Mc32crbp, although three size classes of polyadenylated mRNAs are detected. Transcription rate and steady state amounts of mRNA are developmentally regulated and light controlled with strong transcriptional activity as functional chloroplasts are established, and with lower maintenance activity thereafter. Upon salt stress, the rate of transcription decreases, although transcript levels increase. Accompanying stress, a change in the distribution of transcript size classes is observed as the longest transcript with an untranslated 3′ end of 381 nucleotides increases relative to transcripts with shorter 3′ ends. The long transcript is characterized by the presence of five sequence elements in the 3′-untranslated region that are present in cRBP mRNAs from a variety of plants, although not all elements are found in each mRNA. The results may indicate a mechanism by which mRNA levels of constitutively light-regulated genes may be modulated without enhanced transcription in response to environmental cues.
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  • 28
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    Plant molecular biology 26 (1994), S. 1023-1030 
    ISSN: 1573-5028
    Keywords: immunoglobulin genes ; gene expression ; transgenic plants
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  • 29
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    Plant molecular biology 26 (1994), S. 1065-1071 
    ISSN: 1573-5028
    Keywords: Brassica ; polyploid ; gene expression ; RT-PCR ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One of the essential issues regarding evolution of polyploid species is how duplicate genes are expressed. Most studies on gene expression in polyploids have been based on isozyme analyses; RNA analysis has not been widely used partially due to difficulties in distinguishing homologous transcripts which usually have the same length and similar or almost identical sequences. In this study, a method combining RT-PCR with RFLP was used to analyze transcripts of homologous genes in natural and synthetic Brassica amphidiploids. Sequences coding for several known genes were selected and used to synthesize gene-specific primers. Total RNAs were used as templates for RT-PCR to amplify homologous transcripts in three diploid parental species, three cultivated amphidiploid species and six synthetic amphidiploids. For each gene, initial PCR products amplified in all species had identical length; however, homologous transcripts in the diploid and amphidiploid species could be distinguished after digesting the PCR products with restriction enzymes. Preliminary results based on three genes indicated that both transcripts from the diploid parents were expressed in the synthetic and natural amphidiploids. This study represents the first application of RT-PCR and RFLP analysis to investigate expression of homologous genes in higher plants. The technique is a sensitive, simple and efficient method for distinguishing homologous transcripts in a mixed RNA population and can be applied to many types of studies on expression of homologous genes.
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  • 30
    ISSN: 1573-5028
    Keywords: Calvin cycle genes ; gene expression ; SBPase ; Triticum aestivum
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    Topics: Biology
    Notes: Abstract We report here the isolation and nucleotide sequence of genomic clones encoding the chloroplast enzyme sedoheptulose-1,7-bisphosphatase (SBPase) from Arabidopsis thaliana. The coding region of this gene contains eight exons (72–76 bp) and seven introns (75–91 bp) and encodes a polypeptide of 393 amino acids. Unusually, the 5′ non-coding region contains two additional AUG codons upstream of the translation initiation codon. A comparison of the deduced Arabidopsis and wheat SBPase polypeptide sequences reveals 78.6%, identity. Expression studies showed that the level of SBPase mRNA in Arabidopsis and wheat is regulated in a light-dependent manner and is also influenced by the developmental stage of the leaf. Although the Arabidopsis SBPase gene is present in a single copy, two hybridizing transcripts were detected in some tissues, suggesting the presence of alternate transcription start sites in the upstream region.
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  • 31
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; Brassica napus ; gene expression ; Nicotiana tabacum ; retrotransposon
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    Topics: Biology
    Notes: Abstract The expression of the tobacco (Nicotiana tabacum) retrotransposon Tntl has previously been shown to be strongly regulated and driven from the 5′ long terminal repeat (LTR). We report here that the Tntl LTR can promote activity of the β-glucuronidase (GUS) reporter gene in two heterologous species of the Brassicaceae family, namely rapessed (Brassica napus) and Arabidopsis thaliana. The translational LTR-GUS fusion was active in transient expression studies performed with tobacco and rapeseed protoplasts, indicating that the LTR sequences are recognized in heterologous species. Our results also showed that Tntl LTR-promoted GUS expression in transgenic Arabidopsis is strongly regulated, and that, in contrast to tobacco, hormonal activation plays a significant role in the expression of the Tntl LTR in Arabidopsis. LTR sequences were shown to be more effective than the CaMV 35S enhancer region in transient expression studies performed with tobacco or rapessed protoplasts; and substitution of the LTR sequences upstream from the major transcriptional start with the CaMV 35S enhancer region gave high levels of expression in transgenic tobacco and Arabidopsis leaves, suggesting that a Tntl element with similar substitutions in its 5′ LTR might be suited for gene-tagging experiments in heterologous species.
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  • 32
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    Plant molecular biology 26 (1994), S. 617-630 
    ISSN: 1573-5028
    Keywords: ABA ; barley ; gene expression ; Hordeum vulgare ; phylogeny ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A single-copy barley gene, HVA1, encoding a class 3 late embryogenesis-abundant protein, can be induced by either treatment with abscisic acid (ABA) or by stress conditions such as drought, cold, heat and salinity. We have isolated an HVA1 genomic clone containing about 400 bp of 5′-upstream sequence, a single 109 bp intron, and the full coding sequence. Linker scan mutagenesis and transient expression studies were used to test the function of four HVA1 promoter elements conserved in ABA-responsive genes. Mutations in two of these elements, the C box and the putative ABRE 1 (ABA-responsive element) containing an ACGT core, resulted in no significant change in transcription level or ABA induction. In contrast, mutations of the other two elements, putative ABRE 2 & 3 cause the level of transcription to drop to 10–20% of that obtained with the wild-type promoter indicating that the high level of expression of HVA1 is dependent on both pABRE 2 & 3. Interestingly, despite their low level of expression, the mutated promoters still gave more than 20-fold induction in response to ABA treatment. We suggest that the ABA induction of barley HVA1 gene is governed by a complex consisting of pABRE 2 & 3 working together to regulate the absolute level of expression, and either of these elements or a possible third element may regulate ABA inducibility. Phylogenetic analysis by parsimony indicates that the barley HVA1 and wheat pMA2005 sequences share a recent common ancester. These two genes are closely related to the carrot Dc3 and cotton D-7 genes with which they share a similar structural gene organization.
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  • 33
    ISSN: 1573-5028
    Keywords: gene expression ; Kunitz-type proteinase inhibitor ; potato (Solanum tuberosum, L.) ; soybean C-II inhibitor
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    Topics: Biology
    Notes: Abstract Antiserum against a potato Kunitz-type proteinase inhibitor (PKPI) expressed in Escherichia coli was produced. In immunoblotting assays of proteins from potato tubers cultured in vitro, three proteins reacted to the antiserum, two of 20 kDa and one of 10 kDa. Their N-termini were sequenced. While the 20 kDa proteins showed 59 and 90% identity to PKPI, the 10 kDa one had 65% identity to soybean C-II proteinase inhibitor. Characterization of the temporal expression of these proteins showed that both could be detected from 10 days after induction of tuberization (DAI) in vitro, but the times when maximum amounts of PKPI and 10 kDa protein could be detected were different, corresponding to 22 and 32 DAI, respectively. The amounts of these proteins decreased in the following stages, and no positive reaction of the antiserum with mature tuber proteins could be found. The 20 kDa proteins were also detected in early stages of development of potato tubers grown in the field, indicating that these proteins are expressed during normal tuber development, and differ from the PKPIs reported previously.
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  • 34
    ISSN: 1573-5028
    Keywords: anthocyanins ; cDNA cloning ; flavonoids ; gene expression ; genomic organization ; stilbenes ; Vitis vinifera L
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    Topics: Biology
    Notes: Abstract Genes involved in flavonoid and stilbene biosynthesis were isolated from grape (Vitis vinifera L.). Clones coding for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydoxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX) and UDP glucose:flavonoid 3-O-glucosyl transferase (UFGT), were isolated by screening a cDNA library, obtained from mRNA from seedlings grown in light for 48 h using snapdragon (Antirrhinum majus) and maize heterologous probes. A cDNA clone coding for stilbene synthase (StSy) was isolated by probing the library with a specific oligonucleotide. These clones were sequenced and when the putative products were compared to the published amino acid sequence for corresponding enzymes, the percentages of similarity ranged from 65% (UFGT) to 90% (CHS and PAL). The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StSy genes belong to large multigene families, while the others are present in one to four copies per haploid genome. The steady-state level of mRNAs encoded by the flavonoid biosynthetic genes as determined in young seedlings is coordinately induced by light, except for PAL and StSy, which appear to be constitutively expressed.
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  • 35
    ISSN: 1573-5028
    Keywords: cDNA sequence ; cystine-rich proteins ; gene expression ; puroindolines ; tryptophan-rich domain ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From a mid-maturation seed cDNA library we have isolated cDNA clones encoding two Triticum aestivum puroindolines. Puroindoline-a and puroindoline-b, which are 55% similar, are basic, cystine-rich and tryptophan-rich proteins. Puroindolines are synthezised as preproproteins which include N- and C-terminal propeptides which could be involved in their vacuolar localization. The mature proteins have a molecular mass of 13 kDa and a calculated isoelectric point greater than 10. A notable feature of the primary structure of puroindolines is the presence of a tryptophan-rich domain which also contains basic residues. A similar tryptophan-rich domain was found within an oat seed protein and a mammalian antimicrobial peptide. The ten cysteine residues of puroindolines are organized in a cysteine skeleton which shows similarity to the cysteine skeleton of other wheat seed cystine-rich proteins. Northern blot analysis showed that puroindoline genes are specifically expressed in T. aestivum developing seeds. No puroindoline transcripts as well as no related genes were detected in Triticum durum. The identity of puroindolines to wheat starch-granule associated proteins is discussed as well as the potential role of puroindolines in the plant defence mechanism.
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  • 36
    ISSN: 1573-5028
    Keywords: aspartate aminotransferase ; C4 photosynthesis ; gene expression ; gene structure ; isozyme
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    Topics: Biology
    Notes: Abstract The cytosolic and mitochondrial isozymes of aspartate aminotransferase (AspAT) function in the C4 photosynthetic cycle in NAD-malic enzyme-type C4 plants and are expressed at high levels in mesophyll cells and bundle sheath cells, respectively. We constructed a genomic library from Panicum miliaceum, a NAD-malic enzyme-type C4 plant, and cloned the genes for these isozymes. The sequence of the cloned gene for cytosolic AspAT spans 7800 bp and consists of 12 exons. The sequence of the cloned gene for mitochondrial AspAT spans 9000 bp and consists of 10 exons. The results of primer-extension analysis suggest that transcription may be initiated from multiple adjacent sites. Both genes have significant GC-rich regions around the site of initiation of transcription, and these regions showed no CpG suppression. The 5′-flanking regions of both genes include several short sequences similar to the regulatory elements found in other genes for components of the photosynthetic machinery. In particular, the cytosolic AspAT gene contains sequences similar to nuclear protein-binding sites in other mesophyll-expressed C4 photosynthetic genes and the mitochondrial AspAT gene contains elements for light-sensitive and constitutive expression of a bundle sheath-expressed gene. The results of Southern analysis indicated that there are at least two genes that encode each isozyme in the genome of P. miliaceum. A comparison of nitron-insertion positions between AspAT genes of plants and animals revealed that several introns are located at identical positions. On the basis of a phylogenetic tree among AspATs and tyrosine aminotransferase, we have shown that the introns of aminotransferase genes antedate the divergence of eubacteria, archaebacteria, and eukaryotes.
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  • 37
    ISSN: 1573-5028
    Keywords: activating sequence ; gene expression ; glycine-rich protein ; tobacco ; vascular expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bean grp1.8 full-length promoter is specifically active in vascular tissue during normal development of tobacco. Deletion of a negative regulatory element resulted in ectopic activity of the promoter in cortical cells of hypocotyls, roots and stems. A 169 bp fragment (−205 to −36) of the grp1.8 promoter conferred vascular-specific expression to CaMV 35S minimal promoters whereas a 141 bp fragment (−205 to −64) strongly activated these minimal promoters both in vascular and cortical cells. These experiments defined a new regulatory element (VSE) that is essential for vascular-specific expression and is located between −64 and −36. The 141 bp grp1.8 promoter sequence had enhancer-like properties as it was active in both orientations. A 24 bp sequence (bp −119 to −96, corresponding to the SE1 regulatory element) enhanced expression from several minimal promoters strongly but unspecifically, whereas a 26 bp sequence (−98 to −73, corresponding to the RSE regulatory element) induced vascular-specific expression. Thus, the grp1.8 promoter is regulated by a combinatorial mechanism that can integrate the action of different, non-additively acting regulatory elements into vascular-specific expression.
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  • 38
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    Plant molecular biology 26 (1994), S. 805-816 
    ISSN: 1573-5028
    Keywords: Dehydrin ; gene expression ; pea (Pisum sativum L.) ; cognate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dehydrins are a family of proteins characterised by conserved amino acid motifs, and induced in plants by dehydration or treatment with ABA. An antiserum was raised against a synthetic oligopeptide based on the most highly conserved dehydrin amino acid motif, the lysine-rich block (core sequence KIKEK-LPG). This antiserum detected a novel M r 40 000 polypeptide and enabled isolation of a corresponding cDNA clone, pPsB61 (B61). The deduced amino acid sequence contained two lysine-rich blocks, however the remainder of the sequence differed markedly from other pea dehydrins. Surprisingly, the sequence contained a stretch of serine residues, a characteristic common to dehydrins from many plant species but which is missing in pea dehydrin. The expression patterns of B61 mRNA and polypeptide were distinctively different from those of the pea dehydrins during seed development, germination and in young seedlings exposed to dehydration stress or treated with ABA. In particular, dehydration stress led to slightly reduced levels of B61 RNA, and ABA application to young seedlings had no marked effect on its abundance. The M r 40 000 polypeptide is thus related to pea dehydrin by the presence of the most highly conserved amino acid sequence motifs, but lacks the characteristic expression pattern of dehydrin. By analogy with heat shock cognate proteins we refer to this protein as a dehydrin cognate.
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  • 39
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    Plant molecular biology 26 (1994), S. 1529-1555 
    ISSN: 1573-5028
    Keywords: gibberellin ; growth ; development ; perception ; receptor ; gene expression ; signal transduction ; response mutant ; calcium
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  • 40
    ISSN: 1573-5028
    Keywords: β-tubulin ; cDNA ; rice ; monocot ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two cDNA clones encoding two different β-tubulins, RTUB-1 and RTUB-2, were isolated from a rice cDNA library and their nucleotide sequences were analyzed. The deduced amino acid sequences showed amino acid sequence identity between 92% and 97% with other plant β-tubulins. Southern blot analysis using gene-specific and coding-region probes suggested that β-tubulins in rice are encoded by multigene families. The two cDNA clones represent two subfamilies of rice tubulins. RTUB-1 and RTUB-2, consisting of 3 to 4 genes and a single gene, respectively. The transcript levels of RTUB-1 and RTUB-2 genes were higher in actively elongating tissues such as etiolated shoot tissues and light-grown root tissues of four-day old seedlings.
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  • 41
    ISSN: 1432-1890
    Keywords: Nicotiana ; Glomus species ; arbuscular mycorrhiza ; gene expression ; specific polypeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in gene expression were studied during the establishment of arbuscular mycorrhizal symbiosis in tobacco roots from an amphidiploid hybrid Nicotiana glutinosa x N. debneyi. Polypeptide patterns from control roots and from roots infected by Glomus mosseae or G. intraradices were resolved by two-dimensional polyacrylamide gel electrophoresis and followed in a time-course analysis. Arbuscular mycorrhizal infection led to significant modifications in polypeptide patterns with: (a) decreased amounts of some polypeptides, (b) increased accumulation of others, and (c) appearance of newly-induced polypeptides. Comparisons made during infection development by the two Glomus species demonstrated that protein modifications changed in relation to the mycorrhizal state of the tobacco roots.
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  • 42
    ISSN: 1573-9368
    Keywords: α-actin ; transgenic mice ; gene expression ; muscle ; embryos ; lacZ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transgenic mice carrying a chimaeric transgene containing 730 bp of the 5′-flanking sequences and the entire first intron of the rat α-skeletal actin gene fused to thelacZ reporter gene have been produced by microinjection. ThelacZ reporter gene was used to verify the suitability of using the rat α-actin promoter elements to target expression of genes of agricultural and therapeutic value exclusively to skeletal and heart muscle cells and fibres of transgenic mice. Expression of the transgene indicates a tightly regulated developmental and muscle specific control of the rat α-skeletal actin gene, making it a useful promoter for gene targeting to muscle tissues. The cells destined to form muscle tissues in these transgenic mice are readily visualized in intact embryos by staining for β-galactosidase activity, making them a suitable animal model for studying the origin and development of skeletal and cardiac muscle tissues.
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  • 43
    ISSN: 1573-9368
    Keywords: alcohol dehydrogenase ; Arabidopsis thaliana ; functional complementation ; gene expression ; Nicotiana plumbaginifolia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An alcohol dehydrogenase-deficient (ADH) mutant ofNicotiana plumbaginifolia, selected on the basis of ethanol resistance, was restored for ADH activity by transformation with anAdh gene fromArabidopsis thaliana expressed under the control of its own promoter or the CaMV 35S promoter. The expression in various organs (seed, root, leaf and pollen) was analysed at the protein and RNA levels as well as byin situ detection of ADH activity. The analysis of spatial and temporal regulation of theA. thaliana Adh gene expression suggests that ADH expression is controlled at the transcriptional level.
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  • 44
    ISSN: 1573-4986
    Keywords: lectin ; gene expression ; cell-cell adhesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract BJ38 is a galactose/lactose-specific lectin (M r ∼ 38000) found at one pole ofBradyrhizobium japonicum. It has been implicated in mediating the adhesion of the bacteria to soybean roots, leading to the establishment of a nitrogen-fixing symbiosis. When the ligand lactose is added to cultures of the bacteria for at least 1 h prior to harvesting the cells for BJ38 isolation, the yield of the protein was found to be elevated in a dose-dependent fashion. Half maximal stimulation was observed at ∼ 50 µm; the effect was saturated at ∼ 1mm, where a 10-fold higher yield of BJ38 was obtained. Saccharides with a lower affinity for BJ38 than lactose yielded a correspondingly smaller induction effect when compared at a concentration of 1mm. The higher level of BJ38 induced by lactose is also manifested by an elevated amount of BJ38 detectable at the cell surface and by a higher number ofB. japonicum cells adsorbed onto soybean cells. Surprisingly, the induction of BJ38 expression seen with lactose was also observed with certain, but not all, flavonoids that induce thenod genes of the bacteria; genistein mimicked the induction observed with lactose, whereas luteolin failed to stimulate BJ38 production.
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  • 45
    ISSN: 1573-0778
    Keywords: Baculovirus ; cell culture ; Drosophila ; gene expression ; insect cell ; metallothionein promoter ; recombinant protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this report, we compare two different expression systems: baculovirus/Sf9 and stable recombinantDrosophila Schneider 2 (S2) cell lines. The construction of a recombinant S2 cell line is simple and quick, and in batch fermentations the cells have a doubling time of 20 hours until reaching a plateau density of 20 million cells/ml. Protein expression is driven by theDrosophila Metallothionein promoter which is tightly regulated. When expressed in S2 cells, the extracellular domain of human VCAM, an adhesion molecule, is indistinguishable from the same protein produced by baculovirus-infected Sf9 cells. Additionally, we present data on the expression of a seven trans-membrane protein, the dopamine D4 receptor, which has been successfully expressed in both systems. The receptor integrates correctly in the S2 membrane, binds [3H]spiperone with high affinity and exhibits pharmacological characteristics identical to that of the receptor expressed in Sf9 and mammalian cells. The general implications for large scale production of recombinant proteins are discussed.
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  • 46
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    Photosynthesis research 39 (1994), S. 475-489 
    ISSN: 1573-5079
    Keywords: DNA repair ; flavonoids ; gene expression ; oxidative stress ; photosynthesis ; promoter
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    Topics: Biology
    Notes: Abstract Influx of solar UV-B radiation (280–320 nm) will probably increase in the future due to depletion of stratospheric ozone. In plants, there are several targets for the deleterious UV-B radiation, especially the chloroplast. This review summarizes the early effects and responses of low doses of UV-B at the molecular level. The DNA molecules of the plant cells are damaged by UV due to the formation of different photoproducts, such as pyrimidine dimers, which in turn can be combatted by specialized photoreactivating enzyme systems. In the chloroplast, the integrity of the thylakoid membrane seems to be much more sensitive than the activities of the photosynthetic components bound within. However, the decrease of mRNA transcripts for the photosynthetic complexes and other chloroplast proteins are among very early events of UV-B damage, as well as protein synthesis. Other genes, encoding defence-related enzymes, e.g., of the flavonoid biosynthetic pathway, are rapidly up-regulated after commencement of UV-B exposure. Some of the cis-acting nucleotide elements and trans-acting protein factors needed to regulate the UV-induced expression of the parsley chalcone synthase gene are known.
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    Photosynthesis research 39 (1994), S. 413-425 
    ISSN: 1573-5079
    Keywords: elevated CO2 ; gene expression ; Rubisco ; rbcL ; rbcS
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    Topics: Biology
    Notes: Abstract In this review we discuss how the photosynthetic apparatus, particularly Rubisco, acclimates to rising atmospheric CO2 concentrations (ca). Elevated ca alters the control exerted by different enzymes of the Calvin cycle on the overall rate of photosynthetic CO2 assimilation, so altering the requirement for different functional proteins. A decreased flux of carbon through the photorespiratory pathway will decrease requirements for these enzymes. From modeling of the response of CO2 uptake (A) to intracellular CO2 concentration (ci) it is shown that the requirement for Rubisco is decreased at elevated ca, whilst that for proteins limiting ribulose 1,5 bisphosphate regeneration may be increased. This balance may be altered by other interactions, in particular plasticity of sinks for photoassimilate and nitrogen supply; hypotheses on these interactions are presented. It is speculated that increased accumulation of carbohydrate in leaves developed at elevated ca may signal the ‘down regulation’ of Rubisco. The molecular basis of this ‘down regulation’ is discussed in terms of the repression of photosynthetic gene expression by the elevated carbohydrate concentrations. This molecular model is then used to predict patterns of acclimation of perennials to long term growth in elevated ca.
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  • 48
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    Journal of bioenergetics and biomembranes 26 (1994), S. 301-310 
    ISSN: 1573-6881
    Keywords: Mitochondrial encephalomyopathy ; mitochondrial DNA ; gene expression ; protein translation
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    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Large-scale deletions and tRNA point mutations in mitochondrial DNA (mtDNA) are associated with a variety of different mitochondrial encephalomyopathies. Skeletal muscle in these patients shows a typical pathology, characterized by the focal accumulation of large numbers of morphologically and biochemically abnormal mitochondria (ragged-red fibers). Both mtDNA deletions and tRNA point mutations impair mitochondrial translation and produce deficiencies in oxidative phosphorylation. However, mutant and wild-type mtDNAs co-exist (mtDNA heteroplasmy) and the translation defect is not expressed until the ratio of mutant: wild-type mtDNAs exceeds a specific threshold. Below the threshold the phenotype can be rescued by intramitochondrial genetic complementation. The mosaic expression of the skeletal muscle pathology is thus determined by both the cellular and organellar distribution of mtDNA mutants.
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  • 49
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    The European physical journal 349 (1994), S. 219-222 
    ISSN: 1434-601X
    Keywords: 21.60.Jz ; 36.40.+d
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    Topics: Physics
    Notes: Abstract We discuss and compare the gross features of resonance excitations in nuclei and metal clusters. We point out the phenomenon of ”jellium scaling” which means that different materials for metal clusters all give similar resonance spectra and we discuss the various effects which determine the exact position of the resonance.
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  • 50
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    Antonie van Leeuwenhoek 66 (1994), S. 151-164 
    ISSN: 1572-9699
    Keywords: purple non-sulfur bacteria ; Rhodobacter ; photosynthesis ; CO2 fixation ; anaerobic respiration ; gene expression
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    Topics: Biology
    Notes: Abstract Purple non-sulfur phototrophic bacteria, exemplifed byRhodobacter capsulatus andRhodobacter sphaeroides, exhibit a remarkable versatility in their anaerobic metabolism. In these bacteria the photosynthetic apparatus, enzymes involved in CO2 fixation and pathways of anaerobic respiration are all induced upon a reduction in oxygen tension. Recently, there have been significant advances in the understanding of molecular properties of the photosynthetic apparatus and the control of the expression of genes involved in photosynthesis and CO2 fixation. In addition, anaerobic respiratory pathways have been characterised and their interaction with photosynthetic electron transport has been described. This review will survey these advances and will discuss the ways in which photosynthetic electron transport and oxidation-reduction processes are integrated during photoautotrophic and photoheterotrophic growth.
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    Journal of statistical physics 76 (1994), S. 703-723 
    ISSN: 1572-9613
    Keywords: Seismology ; migration ; scalar wave equation ; parallel computing
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    Topics: Physics
    Notes: Abstract Prospecting for oil and gas resources poses the problem of determining the geological structure of the earth's crust from indirect measurements. Seismic migration is an acoustic image reconstruction technique based on the inversion of the scalar wave equation. Extensive computation is necessary before reliable information can be extracted from large sets of recorded data. In this paper a collection of “industrial” migration techniques, each giving rise to a data parallel algorithm, is outlined. Computer simulations on synthetic seismic data illustrate the problem and the approach.
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    Antonie van Leeuwenhoek 65 (1994), S. 245-250 
    ISSN: 1572-9699
    Keywords: Aspergillus ; gene expression ; heterologous protein ; protein secretion ; Trichoderma
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    Topics: Biology
    Notes: Abstract Despite the naturally high capacity for protein secretion by many species of filamentous fungi, secteted yields of many heterologous proteins have been comparatively low. The strategies for yield improvement have included the use of strong homologous promoters, increased gene copy number, gene fusions with a gene encoding a naturally well-secreted protein, protease-deficient host strains and screening for high yields following random mutagenesis. Such approaches have been effective with some target heterologous proteins but not others. Approaches used in heterologous protein production from filamentous fungi are discussed and a perspective on emerging strategies is presented.
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    Antonie van Leeuwenhoek 65 (1994), S. 331-347 
    ISSN: 1572-9699
    Keywords: photoactive proteins ; photoreceptors ; chromophores ; energy transduction ; light signalling ; phototaxis ; gene expression
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    Topics: Biology
    Notes: Abstract The field of photobiology is concerned with the interactions between light and living matter. For Bacteria this interaction serves three recognisable physiological functions: provision of energy, protection against excess radiation and signalling (for motility and gene expression). The chemical structure of the primary light-absorbing components in biology (the chromophores of photoactive proteins) is surprisingly simple: tetrapyrroles, polyenes and derivatised aromats are the most abundant ones. The same is true for the photochemistry that is catalysed by these chromophores: this is limited to light-induced exciton- or electron-transfer and photoisomerization. The apoproteins surrounding the chromophores provide them with the required specificity to function in various aspects of photosynthesis, photorepair, photoprotection and photosignalling. Particularly in photosynthesis several of these processes have been resolved in great detail, for others at best only a physiological description can be given. In this contribution we discuss selected examples from various parts of the field of photobiology of Bacteria. Most examples have been taken from the purple bacteria and the cyanobacteria, with special emphasis on recently characterised signalling photoreceptors inEctothiorhodospira halophila and inFremyella diplosiphon.
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    Genetic resources and crop evolution 41 (1994), S. 151-158 
    ISSN: 1573-5109
    Keywords: Triticum aestivum ; Aegilops tauschii (syn. Ae. squarrosa) ; Erysiphe graminis f. sp. tritici resistance genes ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A collection of 400 Ae. tauschii (syn. Ae. squarrosa) Coss. accessions were screened for powdery mildew resistance based on the response patterns of 13 wheat cultivars/lines possessing major resistance genes to nine differential mildew isolates. 106 accessions showed complete resistance to all isolates, and 174 accessions revealed isolate-specific resistance, among which were 40 accessions exhibiting an identical response pattern as wheat cultivar ‘Ulka/*8Cc’ which is known to possess resistance gene Pm2. Expression of both complete and isolate-specific resistance from Ae. tauschii was observed in some synthetic hexaploid wheats derived from four mildew susceptible T. durum Desf. parents, each crossed with five to 38 resistant diploid Ae. tauschii accessions. Synthetic amphiploids involving different combinations of T. durum and Ae. tauschii generally showed a decrease in resistance compared with that expressed by the Ae. tauschii parental lines.
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  • 55
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; gene expression ; oligomerization ; phosphorylation-dephosphorylation cascade ; PEPC-protein kinase ; site-directed mutagenesis
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    Topics: Biology
    Notes: Abstract Three to four families of nuclear genes encode different isoforms of phosphoenolpyruvate (PEP) carboxylase (PEPC): C4-specific, C3 or etiolated, CAM and root forms. C4 leaf PEPC is encoded by a single gene (ppc) in sorghum and maize, but multiple genes in the C4-dicot Flaveria trinervia. Selective expression of ppc in only C4-mesophyll cells is proposed to be due to nuclear factors, DNA methylation and a distinct gene promoter. Deduced amino acid sequences of C4-PEPC pinpoint the phosphorylatable serine near the N-terminus, C4-specific valine and serine residues near the C-terminus, conserved cysteine, lysine and histidine residues and PEP binding/catalytic sites. During the PEPC reaction, PEP and bicarbonate are first converted into carboxyphosphate and the enolate of pyruvate. Carboxyphosphate decomposes within the active site into Pi and CO2, the latter combining with the enolate to form oxalacetate. Besides carboxylation, PEPC catalyzes a HCO3 --dependent hydrolysis of PEP to yield pyruvate and Pi. Post-translational regulation of PEPC occurs by a phosphorylation/dephosphorylation cascade in vivo and by reversible enzyme oligomerization in vitro. The interrelation between phosphorylation and oligomerization of the enzyme is not clear. PEPC-protein kinase (PEPC-PK), the enzyme responsible for phosphorylation of PEPC, has been studied extensively while only limited information is available on the protein phosphatase 2A capable of dephosphorylating PEPC. The C4 ppc was cloned and expressed in Escherichia coli as well as tobacco. The transformed E. coli produced a functional/phosphorylatable C4 PEPC and the transgenic tobacco plants expressed both C3 and C4 isoforms. Site-directed mutagenesis of ppc indicates the importance of His138, His579 and Arg587 in catalysis and/or substrate-binding by the E. coli enzyme, Ser8 in the regulation of sorghum PEPC. Important areas for further research on C4 PEPC are: mechanism of transduction of light signal during photoactivation of PEPC-PK and PEPC in leaves, extensive use of site-directed mutagenesis to precisely identify other key amino acid residues, changes in quarternary structure of PEPC in vivo, a high-resolution crystal structure, and hormonal regulation of PEPC expression.
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    Cellular and molecular neurobiology 14 (1994), S. 557-568 
    ISSN: 1573-6830
    Keywords: antisense oligonucleotides ; gene expression ; pharmacology ; drug design ; cell cultures ; brain research
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    Topics: Biology
    Notes: Summary 1. Synthetic oligonucleotides can inhibit the expression of a gene in a sequence specific manner on the transcriptional and translational level. These molecules are usually referred to as antisense oligonucleotides. 2. Antisense mediated inhibition of gene expression is a valuable tool to analyze the function of a genein vivo and can also be used for therapeutic gene suppression. 3. A number of factors such as the mode of action, specificity, chemistry, and pharmacology must be carefully considered for the design and successful application of antisense oligonucleotides. 4. Assay systems and controls must be chosen as to assure that the observed biological effects of antisense oligonucleotides do in fact reflect the result of a specific gene inhibition. 5. This article critically discusses these factors in view of the literature and our own experience with a wide range of cell types and animal models, targeting different genes. The emphasis is on the use of phosphorothioate oligodeoxynucleotides in cell cultures,in vivo, and as potential drugs.
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    The European physical journal 29 (1994), S. 45-48 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.90.+q
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    Topics: Physics
    Notes: Abstract A direct measurement of collisionally induced fission of C 60 2+ has been performed. We have measured coincidences between various charged fragments resulting from collisions between C 60 2+ and He atoms. The measurements show that C 60 2+ not only emits C2 units but also breaks up into larger, singly charged parts. In this paper, we report on coincidences between C n + (2≦n≦9) and C m + (42≦m≦48) fragment ions.
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  • 58
    ISSN: 1434-6079
    Keywords: 34.90.+q ; 36.40.+d
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    Topics: Physics
    Notes: Abstract Various fullerene ions are generated in a standard plasma ion source from a vaporized mixture of C60/C70. Except C 60 + and C 70 + , the fullerene ions are formed by fragmentation of C60 or C70 excited by electron impact. Information on the structure and stability of the fullerene ions is obtained by studying unimolecular dissociation and collision-induced fragmentation of C 60 + , C 58 + and C 56 + in H2 and Ar target gases.
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  • 59
    ISSN: 1434-6079
    Keywords: 34.20.−b ; 36.40.+d ; 31.20.Ej
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    Topics: Physics
    Notes: Abstract A detailed study of the intrinsic consistency of the semiempirical method of P. Claverie namely, the effects of the basis set and intramolecular correlation on the multipole distributions of molecular subunits and the influence of the electronic population of each atom in the molecular subunit on its van der Waals radius, is performed on some van der Waals dimers. The validity, limits of this model and the appropriate way to use it is established. In particular, the dependence of the geometry and the interaction energy on the basis set chosen and the intramolecular correlation shows that the multipole distribution involved in the calculation of the electrostatic and polarization terms must be derived from a correlated wave function within an extended basis set. Associated to non local methods for finding stationary points, the method of P. Claverie reproduce reliably the intermolecular geometrical parameters observed for the equilibrium structures and the transition states of the dimer and trimer of acetylene. In addition, a study of the equilibrium structures of the ethylene dimer is presented, the aim of being to clarify the considerable uncertainty in their number and their geometry.
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    The European physical journal 30 (1994), S. 349-356 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 61.55.Hg ; 68.35.Dv
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    Topics: Physics
    Notes: Abstract Density functional theory is used to study the atomic and electronic structures of Na10K10Cs n clusters with up to sixty atoms. The simplifying approximation has been made of replacing the external potential of the ionic background by its spherical average about the cluster centre in the iterative process of solving the Kohn-Sham equations for each geometry tested. The search for the equilibrium geometry is performed by employing the technique of simulated annealing. We have always found segregation of Cs atoms to the surface as well as a rather neat separation of different species in different (radial) regions of the cluster. This layering effect appears to be consistent with a tendency to maximize electronegativity differences. When the cluster is big enough, Cs atoms begin to appear also inside the cluster. Those geometrical effects do not perturb the electronic magic numbers well known for pure alkali metal clusters.
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    The European physical journal 31 (1994), S. 85-93 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 07.75.+h ; 07.77.+p
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    Topics: Physics
    Notes: Abstract The cluster source we use, a low pressure, rare gas condensation cell, is capable of producing clusters containing more than 45 000 atoms or having masses exceeding 2 500 000 amu. Details of this source and the dependence of the cluster size distribution on adjustable working parameters (oven temperature, inert gas pressure, inert gas type) are discussed in this report. Measurements of the mass-dependent velocity distributions of the clusters emitted by the source are presented and compared to a simple model calculation. The clusters are mass-analyzed with a time-of-flight mass spectrometer and detected by a multi-channel plate. The dependence of the detectability of large clusters on the acceleration voltage is investigated.
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    The European physical journal 31 (1994), S. 187-189 
    ISSN: 1434-6079
    Keywords: 36.40.+d
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    Topics: Physics
    Notes: Abstract Collision of Ar cluster ions, Ar n + (n=3−16), with He and Ne atoms was investigated by use of mass spectroscopic techniques. The cross sections for the production of Ar n′ + (n′〈n) were measured as functions of the size of the parent cluster ion and the collision energy (0.1–10 eV in the center-of-mass frame). These results were analyzed in the scheme of hard-sphere spectator collision with RRK theory. It was concluded that the reaction proceeds via collisional excitation of the parent cluster ion and following sequential loss of the constituent Ar atoms.
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  • 63
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    The European physical journal 32 (1994), S. 125-136 
    ISSN: 1434-6079
    Keywords: 31.20.Sy ; 31.20.Rx ; 36.40.+d
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    Topics: Physics
    Notes: Abstract We present an extension of the jellium model for alkali clusters which allows a selfconsistent determination of the jellium background in addition to the Kohn-Sham solution of the electron dynamics. It includes the volume and the surface energy of the ionic distribution. We discuss applications to the shape of clusters and to the position and width of the plasmon resonances.
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  • 64
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    The European physical journal 29 (1994), S. 67-72 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 75.60.Jp ; 76.50.+g
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    Topics: Physics
    Notes: Abstract The deflection of free magnetic metal clusters in a Stern-Gerlach magnetic field is studied. In particular we investigate magnetic resonance effects resulting from lattice anisotropy and cluster rotation. In analogy to small suspended particles in an oscillating magnetic field the anisotropy field fixed to the rotating atomic lattice of the cluster acts on the cluster magnetization like an rf field in NMR experiments. In our calculation we have used the Bloch equations and assumed different anisotropy field symmetries (uniaxial, cubic). A minimum in the magnetization as a function of the Stern-Gerlach field and also of the cluster size, as observed recently, is obtained under certain conditions. However, such a resonance behavior occurs only if the distribution of the rotation frequency ωrot is relatively narrow, while a broad distribution of ωrot yields an almost superparamagnetic behavior. In addition, the strength of the anisotropy field and the relaxation time are important variables which determine the magnetic behavior of the clusters.
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  • 65
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    The European physical journal 29 (1994), S. 81-83 
    ISSN: 1434-6079
    Keywords: 33.80.Eh ; 36.40.+d ; 36.90.+f
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    Topics: Physics
    Notes: Abstract Ionization dynamics of free C60 is investigated after single photon excitation with synchrotron radiation in the energy range between 8.9 eV and 27.6 eV. Upper limits for the time constants describing possible delayed ionization are obtained from peak shape asymmetries in time of flight spectra as a function of excitation energy. The results clearly indicate that delayed ionization is not observed after single photon excitation in contrast to the results obtained in ns-laser MPI experiments.
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  • 66
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    The European physical journal 29 (1994), S. 147-150 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.20.−b
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    Topics: Physics
    Notes: Abstract The limits of stability of small atomic clusters with angular momentum are investigated as a function of the size and charge of the aggregates. Critical angular momenta are obtained in a di-cluster picture from the balance of a cohesive surface-surface interaction and the disruptive centrifugal and electric interactions. The calculation scheme incorporates the mass and charge asymmetry degrees of freedom and it is thus particularly suited to explore cluster-cluster reaction processes. Deformation of the fragments is taken into account.
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    The European physical journal 29 (1994), S. 241-243 
    ISSN: 1434-6079
    Keywords: 21.60.Jz ; 36.40.+d ; 71.10.+x
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    Topics: Physics
    Notes: Abstract Numerical Hartree-Fock calculations on the2S+1 L states arising from 1s 2 1 pv and 1s 2 1p 6 1 pμ open-shell configurations of Nan-type (n≦20) jellium spheres are reported for the first time. TheL, S multiplet energy spread is substancially larger than that expected from earlier estimates of exchange interaction energies. A new way of considering cluster abundance structures in mass spectra emerges from the results.
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  • 68
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    Notes: Abstract The effects of adding molecules on the LIF at 540 nm of a barium atom at the surface of an argon cluster (average size 420) has been investigated. We showed that molecules like ethanol,n-hexane and O2 from stable complexes with ground state barium. In the case of molecules like N2, CH4 and SF6, the collisional quenching of solvated Ba(1 P) is observed. The large quenching rates obtained are interpreted by a surface mobility of the collisional partners. Moreover, we showed that this collisional quenching leads to the ejection of free Ba(3 P 1).
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    The European physical journal 30 (1994), S. 69-75 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.80.Eh ; 82.30.Nr ; 82.40.Dm
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    Topics: Physics
    Notes: Abstract Geometric structures and the energies for the ground and several excited electronic states of a sodium atom bound with one or two ammonia molecules are presented. All self consistent field (SCF) calculations are performed with extended basis sets. Geometry optimization and one electron properties have been performed within the SCF approximation. Excited states have been calculated with the multi-configuration SCF (MCSCF) technique. This system may be viewed as a precursor to solvation in a macroscopic system. The excited state calculations provide important information for spectroscopic studies of these complexes.
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    The European physical journal 32 (1994), S. 257-260 
    ISSN: 1434-6079
    Keywords: 34.20.cf ; 36.40.+d
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    Topics: Physics
    Notes: Abstract A new empirical potential energy function (PEF) is proposed, which is formed from pair-interactions only, and containes the many-body contributions. The PEF satisfies bulk cohesive energy and bulk stability condition. The PEF is parameterized for copper, silver, and gold elements in fcc crystal structure. The elastic constantsC 11 andC 12 and the bulk modulus of the elements are calculated, and the structural stability and energetics of microclusters containing 3 to 7 atoms of the same elements are investigated.
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    The European physical journal 29 (1994), S. 73-80 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 78.40
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    Topics: Physics
    Notes: Abstract We have computed the electronic structure and the imaginary part of the dielectric function of the Au55 cluster using a tight-binding model which takes into account size and boundary effects. Besides the Drude behavior, we obtain anomalous absorption peaks in the infrared region due to the breakdown of the selection rule Δk=0. Taking into account surface coating effects, the onset of the interband absorption above 2.5 eV results to be red shifted, in agreement with the experimental data. As a consequence, we obtain a dramatic increase of the width of the plasmonic absorption peak, which accounts for the experimental optical spectra observed by Kreibig.
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    The European physical journal 31 (1994), S. 125-129 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 73.20.Mf ; 21.60.Cs
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    Topics: Physics
    Notes: Abstract The origin of the plasmon excitation in small metal clusters is studied within the jellium model through ab initio electronic-structure calculations based on the nuclear shell model. In the limit of infinite size, the plasmon classically represents pure harmonic motion of the center of mass of the valence electrons. It is shown that this limit is already well approximated by clusters of only eight electrons.
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    The European physical journal 29 (1994), S. 139-145 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.10.+x ; 82.20.Rp
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    Topics: Physics
    Notes: Abstract In this article, the dynamics of fragmentation of highly excited van der Waals clusters are analyzed. An approach to the characterization of complex cluster fragmentation is described, based on a combination of structural and dynamical analysis of classical trajectories. In this method, the final fragmentation pattern is analyzed by a depth-first search algorithm based on graph theory, which provides a partitioning of the system into intact fragments of various sizes: monomers, dimers, trimers, and higher multimers. With knowledge of the final products, a dynamical analysis is accomplished by tracing back the time dependence of the relevant fragment energies. A transition from oscillatory to constant behavior of these energies indicates that the fragment has become energetically isolated from the parent cluster. This allows an unambiguous definition of the dissociation time of the fragment. The method is applied to the characterization of cluster fragmentation of chemically activated I2Ar 12 * formed in the association reaction I+I(Ar)12→I2+12 Ar. It is found that cluster decomposition channels, leading to the formation of at least one multi-atom fragment, play an important role in the evaporative cooling of I2, in addition to monoatomic sequential evaporation.
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    The European physical journal 30 (1994), S. 57-68 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 64.70.-p
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    Topics: Physics
    Notes: Abstract Using a distance-dependent tight-binding hamiltonian, we have studied the influence of the temperature on the geometries of small alkali clusters (Na4, Na8, and Na20). We have applied a Monte-Carlo thermodynamical method which consists in performing canonical samplings for various temperatures, these samplings being reexpressed in the microcanonical ensemble. This method provides thermodynamical values such as the entropy and the specific heat. Their behaviour shows one phase transition in the case of Na4 and Na8, and two phase transitions for Na20. As concerns Na4 and Na8, the transition occurs at ≈200 K, between a solid-like phase and a phase for which the geometry of these clusters oscillates between numerous shapes. In the case of Na20, the two observed phase transitions can be described as a melting of the surface atoms (at ≈200 K) preliminarily to the fluctuation of an inner icosahedron seed (at ≈300 K).
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    The European physical journal 30 (1994), S. 323-326 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.90.+q
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    Topics: Physics
    Notes: Abstract Electron capture in collisions of C 60 2+ and C 60 3+ molecular ions with atomic and molecular gases has been studied at impact energies around 100 keV. The cross-section dependence on the target-ionization potentials is discussed, and a simple over-barrier model is evoked to explain the energy dependences. The cross sections for endothermic processes are discussed in the light of a simple two-state model, and a general understanding of their behaviour is obtained.
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  • 76
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.50.−s ; 35.20.Gs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The stability of gold cluster ions Au n + (2≦n≦23) has been investigated via collision induced dissociation in a Penning trap. Threshold energies and dissociation channels have been determined. The cluster stability exhibits a pronounced odd — even alternation: Clusters with an odd number of atoms,n, are more stable than the even-numbered ones. Enhanced stabilities are found for Au 3 + , Au 9 + , and Au 19 + in accordance with the Clemenger-Nilsson and the deformed jellium model of delocalized valence electrons. Excited odd cluster ions withn≦15 predominantly decay by evaporation of dimers; all others decay by monomer evaporation. From the dissociation channels estimates of the binding energies are deduced.
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  • 77
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    The European physical journal 31 (1994), S. 95-104 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.10.Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A second order perturbation approach for the evaluation of the splitting and shifting of the infrared vibrational bands of molecular clusters, based on early publications of Buckingham, is presented. The Hamiltonian of the system comprises harmonic- and anharmonic intramolecular vibration terms, as well as the intermolecular potential. The anharmonic contributions of the intramolecular force field and the intermolecular potential are treated as a perturbation. In order to extend the applicability of the approach to homogeneous molecular clusters, the formalism of degenerate perturbation theory is employed. The new approach is applied to methanol clusters from dimer to hexamer for calculating the frequency shifts of the OH stretching mode (ω1=3681.5 cm−1), the CH3 rocking mode (ω7=1074.5 cm−1), and the CO stretching mode (ω8=1033.5 cm−1). The numerical results compare favourably with experimental and previous theoretical data (except for ω1), but with a tendency to overestimate the shifts.
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  • 78
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    The European physical journal 31 (1994), S. 131-134 
    ISSN: 1434-6079
    Keywords: 61.16.Di ; 36.40.+d ; 66.30.−h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cluster-size dependence of alloying behavior in nm-sized atom clusters has been studied by transmission electron microscopy, using clusters in the Au-Cu system. It was revealed that occurrence of rapid spontaneous alloying becomes more difficult with increasing cluster size. In gold clusters of approximately 4 nm in the mean size, a rapid dissolution of copper atoms took place and homogeneously mixed Au-Cu alloy clusters were formed. In gold clusters of approximately 10 nm in the mean size, rapid alloying of copper took place only at a shell-shaped region beneath the free surface of individual clusters and pure gold was retained at the central region of clusters. In gold clusters of approximately 30 nm in the mean size, no rapid alloying of copper was induced. The ease with which spontaneous alloying takes place is discussed in terms of the lattice softening in atom clusters.
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  • 79
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    The European physical journal 31 (1994), S. 191-197 
    ISSN: 1434-6079
    Keywords: 36.40.+d
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    Topics: Physics
    Notes: Abstract Highly charged metal clusters can be easily produced using the technique of multi-step photoionization. The critical sizes at which fission occurs are reported here for alkali metal clusters having charges as high as +7. An interpretation within the framework of the liquid droplet model reveals that the fission process is strongly asymmetric and thermally activated.
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  • 80
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    The European physical journal 32 (1994), S. 249-255 
    ISSN: 1434-6079
    Keywords: 31.20.Ej ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Alkali halide clusters Na n F n have most frequently cuboid structures and Na n F n−1 clusters are derived from Na n F n by removing a F− centre. An excess electron localises on the site of the removed F− ion. In this paper, other kind of clusters are studied at the SCF level: i) The non-cubic structures. ii) The cubic Na n F n−1 for which the excess electron has no defined site. Due to very large size of these species (at least 27 atoms!) some equivalent fictive linear and planar geometries are studied.
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  • 81
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    Bulletin of experimental biology and medicine 117 (1994), S. 122-124 
    ISSN: 1573-8221
    Keywords: gene expression ; c-myc ; Ca-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In the course of adaptation to repeated stress, the expression of the proto-oncogene c-myc found to increase much more rapidly than that of the Ca-ATPase gene. It is suggested that an increase in the level of c-myc expression may activate the structural Ca-ATPase gene and possibly also the heat-shock proteins.
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  • 82
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    Cellular and molecular life sciences 49 (1993), S. 133-137 
    ISSN: 1420-9071
    Keywords: Fetal hemoglobin ; sickle cell anemia ; β thalassemia ; butyrate ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The inherited β-hemoglobinopathies (sickle cell disease and β thalassemia) are the result of a mutation in the adult (β) globin gene. The fetal globin chain, encoded by the γ globin genes, can substitute for the mutated or defective β globin chain, but expression of the γ globin gene is developmentally inactivated prior to birth. Reinducing expression of the normal fetal globin genes is a preferred method of ameliorating sickle cell disease and the β thalassemias. Stimulation of as little as 4–8% fetal globin synthesis in the bone marrow can produce 〉20% fetal hemoglobin in the peripheral circulation, due to enhanced survival of red blood cells containing both sickle and fetal hemoglobin, compared to those containing sickle hemoglobin alone. Butyric acid and butyrate derivatives are generally safe compounds which induce fetal hemoglobin production by stimulating the promoter of the fetal globin genes. An initial trial with the parent compound, delivered as Arginine Butyrate, has demonstrated rapid stimulation of fetal globin expression to levels that have been shown to ameliorate these conditions. Phase 1 trials of an oral butyrate derivative with a long plasma half-life have just begun. These agents now provide a specific new apporach for ameliorating these classic molecular disorders and merit further investigation in larger patient populations.
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  • 83
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    Cellular and molecular life sciences 49 (1993), S. 447-455 
    ISSN: 1420-9071
    Keywords: Proteoglycan ; chondroitin sulfate ; decorin ; gene expression ; tumor stroma ; DNA methylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Tumor stroma is a specialized form of tissue that is associated with epithelial neoplasms. Recent evidence indicates that significant changes in proteoglycan content occur in the tumor stroma and that these alterations could support tumor progression and invasion as well as tumor growth. Our main hypothesis is that the generation of tumor stroma is under direct control of the neoplastic cells and that, via a feedback loop, altered proteoglycan gene expression would influence the behavior of tumor cells. In this review, we will focus primarily on the work from our laboratory related to the altered expression of chondroitin sulfate proteoglycan and its role in tumor development and progression. The connective tissue stroma of human colon cancer is enriched in chondroitin sulfate and the stromal cell elements, primarily colon fibroblasts and smooth muscle cells, are responsible for this biosynthetic increase. These changes can be reproduced in vitro by using either tumor metabolites or co-cultures of human colon carcinoma cells and colon mesenchymal cells. The levels of decorin, a leucine-rich proteoglycan involved in the regulation of matrix assembly and cell proliferation, are markedly elevated in the stroma of colon carcinoma. These changes correlate with a marked increase in decorin mRNA levels and a concurrent hypomethylation of decorin gene, a DNA alteration associated with enhanced gene expression. Elucidation of decorin gene structure has revealed an unexpected degree of complexity in the 5′ untranslated region of the gene with two leader exons that are alternatively spliced to the second coding exon. Furthermore, a transforming growth factor beta (TGF-β)-negative element is present in the promoter region of decorin gene. This regulatory domain is likely to be implicated in the silencing of decorin gene by TGF-β and may contribute to the regulation of this matrix gene in the tumor stroma.
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  • 84
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    Applied physics 56 (1993), S. 215-217 
    ISSN: 1432-0630
    Keywords: 71.25.Mg ; 71.25.Rk ; 71.20.−b ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A tight-binding method which has been previously applied to study the effect of uncorrelated orientational disorder on conduction-band properties is extended here to the case of systems with long-range order and/or short-range correlations. The density of states and conductivity are not highly sensitive to the specific short-range correlations, so long as the system is not too close to being fully ordered. Hence the strong effects of disorder found previously appear to be robust and should play an important role in the interpretation of normal-state properties of A3C60.
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  • 85
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    Applied physics 57 (1993), S. 101-104 
    ISSN: 1432-0630
    Keywords: 73.20.Mf ; 82.65.Pa ; 82.50.−m ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Laser-induced desorption of metal atoms from the surface of small metal particles has been investigated as a function of the shape of the particles and the polarization of the incident laser light. The particles were supported on LiF, quartz or sapphire substrates. In a first set of experiments, the shape of the particles was determined by recording optical transmission spectra with s- and p-polarized light incident under an angle of typically 40° with respect to the surface normal. The metal particles turn out to be oblate, the ratio of the axes perpendicular and parallel to the substrate surface being on the order of 0.5. This ratio decreases with increasing particle size. Also, the particles change shape if the temperature is raised. In further experiments, s- and p-polarized light has been used to stimulate desorption of atoms via surface plasmon excitation. It is found that the desorption rate markedly depends on the polarization of the light. This is explained by excitation of the collective electron oscillation along different axes of the non-spherical particles.
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  • 86
    ISSN: 1573-4919
    Keywords: glucocorticoid receptor ; MMTV ; transcription factors ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The long terminal repeat (LTR) of the mouse mammary tumor virus was used as a template to examine the dual binding parameters of the glucocorticoid-receptor (GR) and a repressor protein termed Inhibitory Factor 1 (IF1). The roceptor binds specifically to the glucocorticoid response element and precludes the binding of IF1 to its juxtaposed binding site within the LTR. When the two DNA targets are separated by the insertion of an additional 52 base pairs, coincident binding of both proteins is observed. Gel retention assays reveal three distinct nucleoprotein complexes. The first complex consists of the receptor and the LTR, the second is comprised of IF1 and DNA and the third is a multiprotein-DNA complex consisting of the GR, IF1 and DNA, migrating at a higher molecular weight position. The inhibition of IF1 binding by the presence of prebound GR leads to the repression of transcription of juxtaposed genes. The GR may act to block access of a sequence, used by the cell to titrate repressor proteins and facilitate the onset of gene expression. (Mol Cell Biochem122: 25–37, 1993)
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  • 87
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    Molecular and cellular biochemistry 122 (1993), S. 147-158 
    ISSN: 1573-4919
    Keywords: PSG transcripts ; gene expression ; PCR ; T lymphocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The presence of PSG in blood cells has been demonstrated by immunohistochemical staining. However, the origin of these proteins is not known. This report examines the expression of the PSG genes in different types of freshly isolated blood cells. RNA isolated from bone marrow and peripheral blood cells of healthy individuals was analyzed for PSG transcripts by reverse transcriptase-polymerase chain reaction using synthetic oligonucleotide primers specific for the PSG genes. The level of expression of the PSG genes in different types of cells exhibited significant individual variation. Trace amounts of PSG transcripts could be detected in polymorphonuclear cells (PMN), monocytes and B lymphocytes while T lymphocytes always contained the highest level of transcript. The expression of PSG genes in the blood cells apparently was not affected by the method of isolation nor by overnight culturing of these cells except in the case when lymphocytes were separated by rosetting with sheep red blood cells. All reported PSG transcripts were detected in blood cells. Both type I and type II transcripts of the PSG genes were detected in blood cells with the exception of type II transcript of PSG5 and PSG11 which were only found in the placenta. Tissue specificity in the expression or alternative splicing of some of the PSG family members was implicated.
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  • 88
    ISSN: 1573-5028
    Keywords: ABA ; cDNA cloning ; freezing tolerance ; gene expression ; osmotin-like protein ; Solanum commersonii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated a cDNA (pA13) of an ABA-responsive gene from suspension cultures of Solanum commersonii. The deduced amino acid sequence of pA13 cDNA revealed 89 and 91% identity with tobacco osmotin and tomato NP24 protein, respectively. The accumulation of the transcript corresponding to pA13 cDNA was regulated by ABA, cold temperature, and low water potential treatments. Cold-induced accumulation of the pA13 transcript was partially suppressed by fluridone, an ABA synthesis inhibitor, and the suppression was restored by exogenous ABA application. The transcript corresponding to pA13 also accumulated in an organ-specific manner in response to ABA or cold treatment.
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  • 89
    ISSN: 1573-5028
    Keywords: α-tubulin ; Arabidopsis ; β-glucuronidase ; gene expression ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Arabidopsis tissues, the pool of tubulin protein is provided by the expression of multiple α-tubulin and β-tubulin genes. Previous evidence suggested that the TUA2 α-tubulin gene was expressed in all organs of mature plants. We now report a more detailed analysis of TUA2 expression during plant development. Chimeric genes containing TUA2 5′-flanking DNA fused to the β-glucuronidase (GUS) coding region were used to create transgenic Arabidopsis plants. Second-generation progeny of regenerated plants were analyzed by histochemical assay to localize GUS expression. GUS activity was seen throughout plant development and in nearly all tissues. The blue product of GUS activity accumulated to the highest levels in tissues with actively dividing and elongating cells. GUS activity was not detected in a few plant tissues, suggesting that, though widely expressed, the TUA2 promoter is not constitutively active.
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  • 90
    ISSN: 1573-5028
    Keywords: wounding ; elicitor ; plant defense ; gene expression ; tuber ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have characterized a genomic clone containing the potato pathogenesis-related genes STH-2 and STH-21. The two genes are found 4 kb apart on the same chromosome and their sequences are highly similar. They present the same transcriptional orientation and are both interrupted by a single intron. A chimaeric gene consisting of 1015 bp of 5′-flanking sequence and part of the first exon of STH-2 fused to the bacterial β-glucuronidase gene was highly-expressed in tubers of transgenic potato plants after wounding and elicitor treatments. The levels of activity observed in these transgenic plants parallel those observed for the accumulation of STH-2 mRNAs under similar conditions. This indicates that cis-acting elements necessary for the proper activation of the gene are present within 1 kb of 5′-flanking sequences. Functional analysis of 5′ deletions of the STH-2/GUS constructs by transient expression in leaf protoplasts revealed the presence of an upstream regulatory sequence between -135 and -52 which contains a TGAC motif, and a possible negative regulatory region between -52 and -28. A factor present in nuclear extracts of wounded potato tubers was found to bind specifically to nucleotides located between -135 to -105, suggesting that this region contains important cis-regulatory elements.
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  • 91
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    Plant molecular biology 21 (1993), S. 429-435 
    ISSN: 1573-5028
    Keywords: azacytidine ; DNA methylation ; gene expression ; inactivation ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied the effect of the demethylating agent azacytidine (azaC) on expression of a β-glucuronidase (GUS) gene transferred to tobacco leaf disks by Agrobacterium-mediated transformation. In a system where no selection was performed, where shoot formation was partially repressed, and where Agrobacterium does not express the GUS gene, we were able to follow the early events of transient and stable expression. Two days after inoculation, 8% of the cells expressed GUS but this proportion rapidly decreased to near zero in the following week. Treatment of leaf disks with azaC just after transformation retarded this inactivation to some extent, while treatment of Agrobacterium prior to transformation increased the frequency of transient expression. Three weeks after inoculation the number of GUS-expressing cells increased 4- to 6-fold in the leaf disks treated with azaC and in the leaf disks transformed with azaC-treated bacteria, while the control remained low. These data suggest that DNA methylation is involved in transgene inactivation and that a large number of silent but potentially active transgenes become integrated.
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  • 92
    ISSN: 1573-5028
    Keywords: transformation ; promoters ; introns ; gene expression ; Oryza sativa ; Hordeum vulgare ; Lolium perenne
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcriptional and translational fusions were made between the reading frame coding for β-D-glucuronidase and sequences of either a constitutively expressed rice gene (GOS2) involved in initiation of translation or a light-inducible rice gene (GOS5). The transient expression of the fusions was studied via particle bombardment of seedling tissues of rice, perennial ryegrass and barley. Furthermore, the results of transient and stable expression were compared for cell suspensions of four rice varieties, one barley variety and one perennial ryegrass variety. TheGOS2-gusA fusions were active in all three monocots studied. Best results were obtained for a construct having both a transcriptional and a translational fusion as well as intron and exon sequences (PORCEHyg). The level of GUS activity was in the range of activities as obtained by the 35S CaMV promoter transcriptionally fused togusA. ThegusA fusion with the light-inducible gene (GOS5) was active in green seedling tissues of all monocots studied. Also a weak expression compared to theGOS2 constructs was found in stably transformed rice callus. ThegusA fusions with the mannopine synthase promoters 1′ and 2′ of the TR-DNA were transiently expressed at lower levels in cell suspensions than PORCEHyg. For stably transformed rice callus the expression of theGOS2-gusA fusion often decreased during prolonged subculture. This decrease in GUS activity and the various GUS-staining phenotypes of transgenic calli are explained by the presence of different cell types in the suspensions used and in the calli. It is presumed that the nature of the cells and their relative contribution in the calli change drastically upon further subculture.
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  • 93
    ISSN: 1573-5028
    Keywords: circadian regulation ; enzyme activity ; gene expression ; light regulation ; nitrate reductase ; phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of a number of plant genes is regulated by an endogenous circadian clock. We report that the Arabidopsis NIA2 (nitrate reductase) gene shows robust circadian oscillations in mRNA accumulation which persist for at least 5 days in plants that have been grown in a light-dark (LD) cycle and then transferred to continuous light (LL). We further show that NIA2 mRNA accumulation oscillates in a circadian fashion in plants that have been grown in LD and then transferred to continuous darkness (DD). Results from nuclear run-on transcriptional analysis suggest that the oscillations in steady-state levels of NIA2 mRNA abundance are not primarily due to changes in transcription but, instead, reflect post-transcriptional regulation. The circadian oscillations in NIA2 mRNA abundance are paralleled by circadian oscillations in nitrate reductase enzyme activity (NR activity) in Arabidopsis plants that have been grown in LD and then transferred either to DD or to LL. Etiolated Arabidopsis seedlings express neither NIA2 mRNA nor NR activity. However, both NIA2 mRNA accumulation and NR activity are induced by exposure to white light. The inductive effects of light on NIA2 mRNA accumulation are due, at least in part, to a very low fluence phytochrome-mediated response. However, the persistence of circadian oscillations in NIA2 mRNA abundance for at least 5 days in LL demonstrates that the circadian clock is capable of overriding or gating the inductive effects of light on NIA2 mRNA accumulation in Arabidopsis for an extended, continuous period of time.
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  • 94
    ISSN: 1573-5028
    Keywords: gene expression ; germination ; transcription factor ; wheat histone gene ; wheat seedling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of genes encoding five histones (H1, H2A, H2B, H3 and H4) and the putative transcription factors HBP-1a (17) and HBP-1b (c38) was examined during early germination and in various tissues of young wheat seedlings. The steady-state levels of core histone (H2A, H2B, H3 and H4) mRNAs were coordinately cell cycle-dependent and paralleled the rate of DNA synthesis during early germination, whereas the expression pattern of the linker histone (H1) genes differed. The five subclass histone genes were actively expressed in the meristematic tissues of young seedlings. Moreover, H1 genes were expressed in leaves that consist mostly of non-proliferating cells, in which core histone genes showed little expression. Quantitative alterations to the mRNAs of the putative transcription factors HBP-1a (17) and HBP-1b (c38) of wheat histone genes were similar to those of the core histone mRNAs, suggesting that both factors function in the cell cycle-dependent expression of wheat core histone genes.
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  • 95
    ISSN: 1573-5028
    Keywords: transformation ; promoters ; introns ; gene expression ; Oryza sativa ; Hordeum vulgare ; Lolium perenne
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcriptional and translational fusions were made between the reading frame coding for β-D-glucuronidase and sequences of either a constitutively expressed rice gene (GOS2) involved in initiation of translation or a light-inducible rice gene (GOS5). The transient expression of the fusions was studied via particle bombardment of seedling tissues of rice, perennial ryegrass and barley. Furthermore, the results of transient and stable expression were compared for cell suspensions of four rice varieties, one barley variety and one perennial ryegrass variety. The GOS2-gusA fusions were active in all three monocots studied. Best results were obtained for a construct having both a transcriptional and a translational fusion as well as intron and exon sequences (PORCEHyg). The level of GUS activity was in the range of activities as obtained by the 35S CaMV promoter transcriptionally fused to gusA. The gusA fusion with the light-inducible gene (GOS5) was active in green seedling tissues of all monocots studied. Also a weak expression compared to the GOS2 constructs was found in stably transformed rice callus. The gusA fusions with the mannopine synthase promoters 1′ and 2′ of the TR-DNA were transiently expressed at lower levels in cell suspensions than PORCEHyg. For stably transformed rice callus the expression of the GOS2-gusA fusion often decreased during prolonged subculture. This decrease in GUS activity and the various GUS-staining phenotypes of transgenic calli are explained by the presence of different cell types in the suspensions used and in the calli. It is presumed that the nature of the cells and their relative contribution in the calli change drastically upon further subculture.
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  • 96
    ISSN: 1573-5028
    Keywords: cold ; low temperature ; barley ; gene expression ; cDNA ; shoot meristem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone of the previously unreported low-temperature-induced gene blt101 was isolated after a differential screen of a cDNA library prepared from low-temperature (6 °C day/2 °C night) grown barley shoot meristems. Southern blot analysis of barley ditelosomic addition lines was used to assign this single-copy gene to the long arm of chromosome 4. Analysis of steady-state levels of blt101 mRNA showed the induction of this transcript in shoot meristems upon transfer of barley (cv. Igri) plants from control (20 °C/15 °C) to low (6 °C/2 °C) temperature treatment. Further, the high level of this transcript is maintained at low temperatures but is reduced on transfer from low to control temperatures. The gene is not induced by drought or by foliar application of ABA. Analysis of segregating doubled haploid lines shows that there is no specific association of this gene with either spring/winter growth habit or frost hardiness. Examination of the spatial expression pattern revealed ubiquitous expression of blt101 in low-temperature (6 °C/2 °C) grown barley shoot meristems, mature leaves and roots.
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  • 97
    ISSN: 1573-5028
    Keywords: embryos ; gene expression ; oleosin ; rapeseed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temporal and spatial expression of oleosin and Δ9-stearoyl-ACP desaturase genes and their products has been examined in developing embryos of rapeseed, Brassica napus L. var. Topas. Expression of oleosin and stearate desaturase genes was measured by in situ hybridisation at five different stages of development ranging from the torpedo stage to a mature-desiccating embryo. The temporal pattern of gene expression varied dramatically between the two classes of gene. Stearate desaturase gene expression was relatively high, even at the torpedo stage, whereas oleosin gene expression was barely detectable at this stage. By the stage of maximum embryo fresh weight, stearate desaturase gene expression had declined considerably while oleosin gene expression was at its height. In contrast to their differential temporal expression, the in situ labelling of both classes of embryo-specific gene showed similar, relatively uniform patterns of spatial expression throughout the embryo sections. Immunogold labelling of ultra-thin sections from radicle tissue with anti-oleosin antibodies showed similar patterns to sections from cotyledon tissue. However, whereas at least three oleosin isoforms were detectable on western blots of homogenates from cotyledons, only one isoform was found in radicles. This suggests that some of the oleosin isoforms may be expressed differentially in the various types of embryo tissue. The differential timing of stearate desaturase and oleosin gene expression was mirrored by similar differences in the timing of the accumulation of their ultimate products, i.e. storage oil and oleosin proteins. Oil-body fractions prepared from young (2.5 mg) embryos contained very little oleosin protein, as examined by SDS-PAGE and western blotting, whereas identically prepared fractions from dry seeds contained over 10% (w/w) oleosin. Dehydration of oil bodies from young embryos resulted in their breakdown and coalescence into large clumps of oil which could not be re-emulsified, even after rehydration. In contrast, the oleosin-rich oil bodies from mature embryos were stable to dehydration and subsequent rehydration. It is suggested that, in developing rapeseed embryos, the accumulation of storage oil and oleosins is not concomitant but that the eventual deposition of oleosins onto the surfaces of storage oil bodies is essential for their stability during seed desiccation.
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  • 98
    ISSN: 1573-5028
    Keywords: allergens ; gene expression ; microsporogenesis ; pectate lyase ; pollen ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone (Zm58.1) was isolated by differential screening from a cDNA library made to mature Zea mays pollen, and shown to be pollen-specific by RNA blot analysis. When this partial-length clone was used to probe a genomic library, a similar but distinct pollen-specific genomic clone (68% sequence identity) was isolated (Zm58.2). The putative proteins coded for by these two clones show sequence homology to several flower-expressed gene products from various plant species, including known pollen allergens from short ragweed (Ambrosia artemisiifolia), and to pectate lyases from the plant pathogenic bacteria Erwinia spp. The two genes map to different chromosomes.
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  • 99
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; blue light ; floral induction ; gene expression ; membrane protein ; DNA sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Continuous irradiation with blue light (400–500 nm) induces flower formation in plantlets of Arabidopsis thaliana (C24) while red light (600–700 nm) is ineffective. This observation started a search for genes that are activated by blue light and initiate the morphogenic programme leading to flower formation. Several genes were identified via their cDNAs. From these clone AthH2, with an open reading frame for a hydrophobic 30.5 kDa polypeptide, was selected for further characterization of the corresponding gene. From a genomic library a DNA fragment of about 6.4 kb was isolated, comprising the coding region as well as 5′-upstream and 3′-downstream flanking segments. The coding region is composed of four exons, which specify a polypeptide of 286 amino acids. Several potential regulatory elements were found between position −670 and −1140 including GA and ABA sequence motifs. The latter could account for the observed induction of the AthH2 gene by ABA. Southern blot analysis of Arabidopsis genomic DNA suggests that the AthH2 gene is encoded by a single-copy gene. Hydropathy plots and secondary structure analysis of the putative polypeptide predict six membrane-spanning domains implicating a function as transmembrane channel protein. It displays significant homology with the proteins TR7a of pea (82%) and RD 28 of A. thaliana (68%).
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  • 100
    ISSN: 1573-4927
    Keywords: muscle protein degradation ; calpain ; gene expression ; genetic variation ; Japanese quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Calpain activity was determined by western blot analysis of steady-state concentrations ofm-calpain (calpain requiring millimolar Ca2 for activation) and also by northern blot analysis of steady-state concentrations of mRNA encodingm-calpain in three lines of quail: a random-bred control line (RR) and two lines selected for body weight, one for increased body weight (LL) and another for decreased body weight (SS). Them-calpain activities in skeletal muscle were higher in the SS line and lower in the LL line. From western blot analysis, enzyme levels of calpain were almost the same for all three lines. At the level of gene expression, the mRNA concentration encodingm-calpain was higher in the LL and lower in the SS line. These results suggest that the regulation of calpain activity in skeletal muscle is a three-step process, regulation at the transcription level, regulation at the enzyme level, and regulation of the activation of calpain.
    Type of Medium: Electronic Resource
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