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  • Arabidopsis  (50)
  • Springer  (50)
  • American Geophysical Union
  • Copernicus
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • 2010-2014
  • 1995-1999  (50)
  • 1996  (50)
Collection
Keywords
Publisher
  • Springer  (50)
  • American Geophysical Union
  • Copernicus
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
Years
  • 2010-2014
  • 1995-1999  (50)
Year
  • 1
    Electronic Resource
    Electronic Resource
    The light-induced reduction of the gravitropic growth-orientation of seedlings of Arabidopsis thaliana (L.) Heynh. is a photomorphogenic response mediated synergistically by the far-red-absorbing forms of phytochromes A and B (1996)
    Springer
    Planta 199 (1996), S. 511-514 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Gravitropism ; phyB-1 ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hypocotyls of dark-grown seedlings of Ara bidosis thaliana exhibit a strong negative gravitropism, which is reduced by red and also by long-wavelength, far-red light treatments. Light treatments using phytochrome A (phyA)- and phytochrome B (phyB)-deficient mutants showed that this response is controlled by phyB in a red/far-red reversible way, and by phyA in a non-reversible, very-low-fluence response. Crosses of the previously analyzed phyB-1 allele (in the ecotype Landsberg erecta background) to the ecotype Nossen wild-type (WT) background resulted in a WT-like negative gravitropism in darkness, indicating that the previously described gravitropic randomization observed with phyB-1 in the dark is likely due to a second mutation independent of that in the PHYB gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195180
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  • 2
    Electronic Resource
    Electronic Resource
    Subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in higher plants: an immunological investigation (1996)
    Springer
    Planta 199 (1996), S. 557-564 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Chlorophyll biosynthesis ; Plastid ; Porphobilinogen deaminase (purification, subcellular location)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase (EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidopsis thaliana (L.) Heynh. has been constructed, and used to transform Escherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-fold) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation of enzyme activity and immuno-gold electron microscopy. The results indicate that the enzyme is confined to plastids in both leaves and roots. The implications of this finding for plant tetrapyrrole synthesis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195187
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  • 3
    Electronic Resource
    Electronic Resource
    The raz1 mutant of Arabidopsis thaliana lacks the activity of a high-affinity amino acid transporter (1996)
    Springer
    Planta 200 (1996), S. 247-253 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Amino acid transport systems ; Gene mapping ; Proline (uptake kinetics)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The raz1 mutant of Arabidopsis thaliana (L.) Heynh. has been selected as resistant to the toxic proline analogue, azetidine-2-carboxylic acid (2AZ). Seedlings of the mutant tolerated fivefold higher concentrations of 2AZ (ED50 = 0.25 mM) than the wild-type seedlings (ED50 = 0.05 mM). The mutant gene was found to be semi-dominant and the corresponding RAZ1 locus was mapped on chromosome 5 at 69.6±1.8 cM. The resistance to 2AZ could be fully and exclusively accounted for by the lower uptake rate of the proline analogue in the mutant. The influx of L-proline in roots of wild-type seedlings could be dissected into two components: (i) a component with a high affinity and a low capacity for l-proline (K m≈20 gmM, V max≈60 nmol·(g FW)-1·h-1) and also a high affinity for L-2AZ (K i≈40 μM) and (ii) a low-affinity, high-capacity component (K m≈5 mM: V max = 1300 nmol·(g FW)-1·h-1). Clearly, the raz1 mutation affects the activity of a high-affinity transporter, because the high-affinity uptake of proline in the mutant was at least fivefold lower than in the wild-type, whereas the low-affinity uptake was unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208315
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  • 4
    Electronic Resource
    Electronic Resource
    Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization (1996)
    Springer
    Planta 200 (1996), S. 229-237 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Cell axialization ; MONOPTEROS gene ; PIN-FORMED gene ; Polar auxin transport ; Vascular development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the embryo of Arabidopsis thaliana (L.) Heynh., formation of the hypocotyl/root axis is initiated at the early-globular stage, recognizable as oriented expansion of formerly isodiametric cells. The process depends on the activity of the gene MONOPTEROS (MP); mp mutant embryos fail to produce hypocotyl and radicle. We have analyzed the morphology and anatomy of mp mutant plants throughout the Arabidopsis life cycle. Mutants form largely normal rosettes and root systems, but inflorescences either fail to form lateral flowers or these flowers are greatly reduced. Furthermore, the auxin transport capacity of inflorescence axes is impaired and the vascular strands in all analyzed organs are distorted. These features of the mutant phenotype suggest that the MP gene promotes cell axialization and cell file formation at multiple stages of plant development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208313
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  • 5
    Electronic Resource
    Electronic Resource
    A second and differentially expressed glutamyl-tRNA reductase gene from Arabidopsis thaliana (1996)
    Springer
    Plant molecular biology 30 (1996), S. 419-426 
    Details
    ISSN: 1573-5028
    Keywords: HEMA ; Glu-tRNA reductase ; Arabidopsis ; porphyrin ; chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 5-Aminolevulinic acid (ALA) is the universal precursor of tetrapyrroles (e.g., chlorophylls and hemes). In the chloroplasts of plants and in several eubacterial species ALA is formed in a two-step process known as the C5 pathway. In the first step, glutamyl-tRNA reductase (GluTR), converts glutamate of glutamyl-tRNA to glutamate 1-semialdehyde (GSA) which is rearranged to ALA by glutamate 1-semialdehyde-2,1-aminomutase (GSA-AM) in the second step. Since ALA formation is a limiting step in chlorophyll biosynthesis, GluTR, which is encoded by the HEMA gene in Arabidopsis thaliana plays a vital role in that biosynthesis. Here we report the occurrence of a second functional HEMA gene (HEMA2) in A. thaliana. This gene was isolated by screening a genomic library with a probe from HEMA1. The nucleotide sequence of the cDNA and the corresponding genomic DNA indicates that the Arabidopsis HEMA2 gene contains two short introns (285 bp and 159 bp). The deduced amino acid sequence predicts a HEMA2 protein of 530 amino acids with 79% identity to the HEMA1-encoded GluTR. The 5′-flanking sequence of the HEMA2 gene includes several motifs (e.g., GT-1 boxes, GATA motifs) similar to light-responsive regulatory elements found in light-inducible genes. Unlike the HEMA1 transcript, which is present in all parts of the plant, HEMA2 is expressed in low levels in roots and flowers. The presence of a second functional HEMA gene in Arabidopsis raises the possibility that two C5 pathways exist in chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049321
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  • 6
    Electronic Resource
    Electronic Resource
    Nucleotide sequence of Chinese rape mosaic virus (oilseed rape mosaic virus), a crucifer tobamovirus infectious on Arabidopsis thaliana (1996)
    Springer
    Plant molecular biology 30 (1996), S. 191-197 
    Details
    ISSN: 1573-5028
    Keywords: tobamovirus ; Cruciferae ; CRMV ; Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The complete nucleotide sequence of Chinese rape mosaic virus has been determined. The virus is a member of the tobamovirus genus of plant virus and is able to infect Arabidopsis thaliana (L.) Heynh systemically. The analysis of the sequence shows a gene array that seems to be characteristic of crucifer tobamoviruses and which is slightly different from the one most frequently found in tobamoviruses. Based on gene organization and on comparisons of sequence homologies between members of the tobamoviruses, a clustering of crucifer tobamoviruses is proposed that groups the presently known crucifer tobamovirus into two viruses with two strains each. A name change of Chinese rape mosaic virus to oilseed rape mosaic virus is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017814
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular cloning of a sulfotransferase in Arabidopsis thaliana and regulation during development and in response to infection with pathogenic bacteria (1996)
    Springer
    Plant molecular biology 30 (1996), S. 995-1008 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; gene expression ; hypersensitive response ; plant-pathogen interactions ; cell suspensions ; sulfotransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone (RaRO47) encoding a sulfotransferase (ST) has been isolated from Arabidopsis cell suspensions. The deduced polypeptide of 302 amino acids is highly related to plant flavonol sulfotrans-ferases (FSTs), characterized for the first time in Flaveria, and also to STs from animal tissue. The expression of the Arabidopsis ST gene(s) corresponding to RaR047 was examined during different developmental stages. It was found that, at the level of steady-state mRNA, expression of gene(s) encoding this ST was rapidly induced in the aerial parts of young seedlings, and during growth of Arabidopsis cell cultures. No expression could be detected in roots. Treatment of Arabidopsis seedlings with hormonal or stress-related compounds, showed that RaR047 mRNA accumulation was more particularly induced in response to salicylic acid and methyl jasmonate. Furthermore, in the leaves of mature plants or in cell suspensions, accumulation of RaR047 mRNA was observed upon infection with bacterial pathogens. This expression was observed preferentially in response to avirulent pathogens causing an hyper-sensitive reaction, as compared to virulent pathogens, which lead to disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020810
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  • 8
    Electronic Resource
    Electronic Resource
    Over-expression of a C-terminal region of phytochrome B (1996)
    Springer
    Plant molecular biology 31 (1996), S. 1079-1082 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; photomorphogenesis ; phytochrome B ; signal transduction ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an attempt to identify domains directly involved in the signal transduction of phytochrome B (phyB), we over-expressed the achromophoric C-terminal half of phyB under control of the CaMV-35S promoter in transgenicArabidopsis. In three independent transgenic lines, we detected accumulation of the introduced protein of predicted size at levels higher than that of the endogenous phyB by immunoblot analysis. Although these transgenic plants did not show any phenotype in the dark, enhancement of the phyB-dependent inhibition of hypocotyl elongation and reduction of the phytochrome A (phyA)-dependent inhibition were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040726
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  • 9
    Electronic Resource
    Electronic Resource
    Nucleotide sequences of nuclear tRNACys genes from Nicotiana and Arabidopsis and expression in HeLa cell extract (1996)
    Springer
    Plant molecular biology 32 (1996), S. 549-552 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; cysteine tRNA genes ; genome organization ; in vitro transcription ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have recently characterized Nicotiana cytoplasmic (cyt) tRNAGCA Cys as novel UGA suppressor tRNA. Here we have isolated its corresponding (NtC1) and a variant (NtC2) gene from a genomic library of Nicotiana rustica. Both tRNACys genes are efficiently transcribed in HeLa cell nuclear extract and yield mature cyt tRNAsCys. Sequence analysis of the upstream region of the RAD51 single-copy gene of the Arabidopsis thaliana genome revealed a cluster of three tRNACys genes which have the same polarity and comprise highly similar flanking sequences. Of the three Arabidopsis tRNACys genes only one (i.e. AtC2) appears to code for a functional gene which exhibits an almost identical nucleotide sequence to NtC1. These are the first sequenced nuclear tDNAsCys of plant origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019108
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  • 10
    Electronic Resource
    Electronic Resource
    Thi1, a thiamine biosynthetic gene inArabidopsis thaliana, complements bacterial defects in DNA repair (1996)
    Springer
    Plant molecular biology 31 (1996), S. 585-593 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; DNA repair ; tolerance ; DNA damage ; thiamine biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract AnArabidopsis thaliana cDNA was isolated by complementation of theEscherichia coli mutant strain BW535 (xth, nfo, nth), which is defective in DNA base excision repair pathways. This cDNA partially complements the methyl methane sulfonate (MMS) sensitive phenotype of BW535. It also partially corrects the UV-sensitive phenothpe ofE. coli AB1886 (uvrA) and restores its ability to reactivate UV-irradiated λ phage. It has an insert of ca. 1.3 kb with an open reading frame of 1047 bp (predicting a protein with a molecular mass of 36 kDa). This cDNA presents a high homology to a stress related gene from two species ofFusarium (sti35) and to genes whose products participate in the thiamine biosynthesis pathway,THI4, fromSaccharomyces cerevisiae andnmt2 fromSchizosaccharomyces pombe. TheArabidopsis predicted polypeptide has homology to several protein motifs: amino-terminal chloroplast transit peptide, dinucleotide binding site, DNA binding and bacterial DNA polymerases. The auxotrophy for thiamine in the yeastthi4::URA3 disruption strain is complemented by theArabidopsis gene. Thus, the cloned gene, namedthi1, is likely to function in the biosynthesis of thiamine in plants. The data presented in this work indicate thatthi1 may also be involved in DNA damage tolerance in plant cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042231
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  • 11
    Electronic Resource
    Electronic Resource
    Characterization of eight new members of the calmodulin-like domain protein kinase gene family from Arabidopsis thaliana (1996)
    Springer
    Plant molecular biology 31 (1996), S. 405-412 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; calcium ; calmodulin ; gene family ; kinase ; phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A family of calcium-responsive protein kinases is abundant in plant cell extracts but has not been identified in animals and fungi. These enzymes have a unique structure consisting of a protein kinase catalytic domain fused to carboxy-terminal autoregulatory and calmodulin-like domains. In this report, we present the amino acid sequences for eight new Arabidopsis cDNA clones encoding isoforms of this enzyme. Three isoforms were expressed as fusion proteins in Escherichia coli and exhibited calcium-stimulated protein kinase activity. We propose CPK as the gene designation for this family of enzymes and describe a phylogenetic analysis for all known isoforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021802
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  • 12
    Electronic Resource
    Electronic Resource
    Characterization of DNA sequences encoding a novel isoform of the 55 kDa B regulatory subunit of the type 2A protein serine/threonine phosphatase of Arabidopsis thaliana (1996)
    Springer
    Plant molecular biology 31 (1996), S. 419-427 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; PP2A regulatory subunit ; serine/threonine phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have indentified a novel gene (AtBβ) encoding a previously uncharacterized isoform of the B regulatory subunit of the type 2A serine/threonine protein phosphatase (PP2A) of Arabidopsis, and show that mRNA derived from the AtBβ gene accumulates in all Arabidopsis organs. In addition, we examined the expression of the three genes encoding the A regulatory subunit of Arabidopsis PP2A and show these genes are expressed in all organs as well. Taken together, our results suggest a myriad of PP2A subunit combinations, possibly with distinct substrate specificities, may occur within each Arabidopsis cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021804
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  • 13
    Electronic Resource
    Electronic Resource
    Proteolysis in plants: mechanisms and functions (1996)
    Springer
    Plant molecular biology 32 (1996), S. 275-302 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; biotechnology ; ClpAP protease ; protein degradation ; 20S and 26S proteasome ; ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Proteolysis is essential for many aspects of plant physiology and development. It is responsible for cellular housekeeping and the stress response by removing abnormal/misfolded proteins, for supplying amino acids needed to make new proteins, for assisting in the maturation of zymogens and peptide hormones by limited cleavages, for controlling metabolism, homeosis, and development by reducing the abundance of key enzymes and regulatory proteins, and for the programmed cell death of specific plant organs or cells. It also has potential biotechnological ramification in attempts to improve crop plants by modifying protein levels. Accumulating evidence indicates that protein degradation in plants is a complex process involving a multitude of proteolytic pathways with each cellular compartment likely to have one or more. Many of these have homologous pathways in bacteria and animals. Examples include the chloroplast ClpAP protease, vacuolar cathepsins, the KEX2-like proteases of the secretory system, and the ubiquitin/26S proteasome system in the nucleus and cytoplasm. The ubiquitin-dependent pathway requires that proteins targeted for degradation become conjugated with chains of multiple ubiquitins; these chains then serve as recognition signals for selective degradation by the 26S proteasome, a 1.5 MDa multisubunit protease complex. The ubiquitin pathway is particularly important for developmental regulation by selectively removing various cell-cycle effectors, transcription factors, and cell receptors such as phytochrome A. From insights into this and other proteolytic pathways, the use of phosphorylation/dephosphorylation and/or the addition of amino acid tags to selectively mark proteins for degradation have become recurring themes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039386
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  • 14
    Electronic Resource
    Electronic Resource
    Isolation of a new mitotic-like cyclin from Arabidopsis: complementation of a yeast cyclin mutant with a plant cyclin (1996)
    Springer
    Plant molecular biology 30 (1996), S. 565-575 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; cell cycle ; cell division ; cyclins ; polymerase chain reaction ; yeast complementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyclins, a large family of proteins, are the regulatory subunits of cyclin-dependent protein kinases that are essential activators of cell cycle progression in eukaryotes. Here we report isolation of a new cyclin cDNA (cyc1bAt) from Arabidopsis cDNA libraries using polymerase chain reaction amplified cyclin-box sequences as probes. The deduced amino acid sequence of the isolated cDNA showed the highest sequence similarity with mitotic cyclins. However, the nucleotide and predicted amino acid sequence of cyc1bAt is different from five other mitotic-like cyclins that have recently been isolated from the same system, indicating that it is a new mitotic-like cyclin. These results, together with previous reports, suggest that there are at least six different mitotic-like cyclins in Arabidopsis. Expression of cyc1bAt in yeast G1 cyclin-minus mutant (DL1) rescued the cyclin-minus phenotype, demonstrating that plant mitotic-like cyclin can complement cyclin function in yeast. Analysis of expression of cyc1bAt in different tissues by reverse transcription-polymerase chain reaction using primers corresponding to a unique region of the cDNA showed that cyc1bAt is differentially expressed in different tissues with highest expression in flowers and no detectable expression in leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049332
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  • 15
    Electronic Resource
    Electronic Resource
    Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn2+-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism (1996)
    Springer
    Plant molecular biology 30 (1996), S. 1169-1179 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; metallothionein-like genes ; MT2 ; smt ; Synechococcus PCC 7942
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zn2+ proteins pervade metabolism and are essential for gene expression. However, no proteins have been ascribed the central roles of Zn2+ donation to, or removal from, metalloproteins, or Zn2+ storage in vegetative plant tissue. In animals, such functions have been proposed for metallothioneins. Plants contain multiple metallothionein-like genes but their predicted products, which differ significantly from animal metallothioneins, remain to be isolated from vegetative tissue and their roles are uncertain. The type 2 metallothionein-like gene from Arabidopsis, MT2, was expressed under the control of Zn2+-responsive elements derived from the cyanobacterial metallothionein divergon, smt. Zn2+-dependent expression of MT2 transcripts in Synechococcus PCC 7942 was confirmed by northern analysis. The Arabidopsis MT2 gene partly complemented Zn2+ hypersensitivity in mutants of Synechococcus PCC 7942 which are functionally deficient in an endogenous Zn2+-metallothionein gene, smtA. MT2 was also expressed as a recombinant fusion protein in Escherichia coli, purified and shown to bind Zn2+ in vitro. The mean pH of half displacement of Zn2+ from MT2 was estimated to be 5.05. This suggests that MT2 has a greater affinity for Zn2+ than phytochelatins. The results presented here reveal that MT2 is capable of binding Zn2+ in vitro, conferring tolerance to elevated [Zn2+] in vivo within cyanobacteria and is likely to compete with other polypeptides for cellular Zn2+ in planta.
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    URL: http://dx.doi.org/10.1007/BF00019550
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  • 16
    Electronic Resource
    Electronic Resource
    Temperature-dependent increase in the DNA-binding activity of a heat shock factor in an extract of tobacco cultured cells (1996)
    Springer
    Plant molecular biology 31 (1996), S. 13-22 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; DNA-binding activity ; HSE (heat shock element) ; HSF (heat shock factor) ; tobacco (Nicotiana tabacum)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The DNA-binding activity of a tobacco heat shock factor (HSF) was induced by heat treatment (37–40 °C) of a cell-free extract that contained extra-nuclear fraction, but not in an extract of isolated nuclei. These observations suggest that an inactive form of HSF can directly recognize and transduce the heat shock signal and that such transduction requires components of the extranuclear fraction. Addition of ATP or of most other nucleoside triphosphates reduced the binding of the HSF to the heat shock element (HSE) in the same extract, and removal of ATP by dialysis from the extract restored the ability of the HSF to bind to DNA. The restored activity of the HSF could be eliminated again by a second addition of ATP. Our observations provide the first example of the involvement of ATP in the regulation of the reversible changes in HSF that control its ability to bind to HSEs in a cell-free extract.
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    URL: http://dx.doi.org/10.1007/BF00020602
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  • 17
    Electronic Resource
    Electronic Resource
    Cloning of the cDNA and genomic clones for glutathione synthetase fromArabidopsis thaliana and complementation of agsh2 mutant in fission yeast (1996)
    Springer
    Plant molecular biology 31 (1996), S. 1093-1104 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; glutathione ; heavy metals ; phytochelatin ; Schizosaccharomyces pombe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glutathione is essential for protecting plants from a range of environmental stresses, including heavy metals where it acts as a precursor for the synthesis of phytochelatins. A 1658 bp cDNA clone for glutathione synthetase (gsh2) was isolated fromArabidopsis thaliana plants that were actively synthesizing glutathione upon exposure to cadmium. The sequence of the clone revealed a protein with an estimated molecular mass of 53858 Da that was very similar to the protein from higher eukaryotes, was less similar to the gene from the fission yeast,Schizosaccharomyces pombe, and shared only a small region of similarity with theEscherichia coli protein. A 4.3 kbSstI fragment containing the genomic clone for glutathione synthetase was also isolated and sequenced. A comparison of the cDNA and genomic sequences revealed that the gene was composed of twelve exons. When theArabidopsis cDNA cloned in a special shuttle vector was expressed in aS. pombe mutant deficient in glutathione synthetase activity, the plant cDNA was able to complement the yeast mutation. Glutathione synthetase activity was measurable in wild-type yeast cells, below detectable levels in thegsh2 - mutant, and restored to substantial levels by the expression of theArabidopsis cDNA. TheS. pombe mutant expressing the plant cDNA had near wild type levels of total cellular thiols,109Cd2+ binding activity, and cadmium resistance. Since theArabidopsis cDNA was under control of a thiamine-repressible promoter, growth of the transformed yeast on thiamine-free medium increased expression of the cDNA resulting in increases in cadmium resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040827
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  • 18
    Electronic Resource
    Electronic Resource
    Lysine and threonine metabolism are subject to complex patterns of regulation in Arabidopsis (1996)
    Springer
    Plant molecular biology 32 (1996), S. 727-734 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; essential amino acids ; lysine ; threonine ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the regulation of lysine and threonine metabolism in plants, we have transformed Arabidopsis thaliana with chimeric genes encoding the two bacterial enzymes dihydrodipicolinate synthase (DHPS) and aspartate kinase (AK). These bacterial enzymes are much less sensitive to feedback inhibition by lysine and threonine than their plant counterparts. Transgenic plants expressing the bacterial DHPS overproduced lysine, but lysine levels were quite variable within and between transgenic genotypes and there was no direct correlation between the levels of free lysine and the activity of DHPS. The most lysine-overproducing plants also exhibited abnormal phenotypes. However, these phenotypes were detected only at early stages of plant growth, while at later stages, new buds emerged that looked completely normal and set seeds. Wild-type plants exhibited relatively high levels of free threonine, suggesting that in Arabidopsis AK regulation may be more relaxed than in other plants. This was also supported by the fact that expression of the bacterial AK did not cause any dramatic elevation in this amino acid. Yet, the relaxed regulation of threonine synthesis in Arabidopsis was not simply due to a reduced sensitivity of the endogenous AK to feedback inhibition by lysine and threonine because growth of wild-type plants, but not of transgenic plants expressing the bacterial AK, was arrested in media containing these two amino acids. The present results, combined with previous studies from our laboratory, suggest that the regulation of lysine and threonine metabolism is highly variable among plant species and is subject to complex biochemical, physiological and environmental controls. The suitability of these transgenic Arabidopsis plants for molecular and genetic dissection of lysine and threonine metabolism is also discussed.
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    URL: http://dx.doi.org/10.1007/BF00020213
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  • 19
    Electronic Resource
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    Noncoding RNA for CR20, a cytokinin-repressed gene of cucumber (1996)
    Springer
    Plant molecular biology 32 (1996), S. 797-808 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; Cucumis ; cytokinin ; noncoding RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The CR20 gene was identified as a cytokinin-repressed gene in excised cotyledons of cucumber. We determined the sequences of some CR20 cDNAs with different structures and sequenced genomic clones for CR20. This gene consisted of three exons, and there were at least three types of transcript, which seemed to be generated by alternative splicing of the second intron. None of the CR20 transcripts included a long open reading frame (ORF). We isolated a cDNA of Arabidopsis thaliana with cucumber CR20 cDNA as a probe. This cDNA for a gene designated AtCR20-1 also lacked a long ORF. A region of 180 nucleotides was conserved in the CR20 RNA of cucumber and the AtCR20-1 RNA of Arabidopsis, although the homology was relatively low when the entire sequences were compared. Each conserved region consisted of seven elements, and seems to form stable secondary structure. These suggest that CR20 RNA may function as an RNA that is not translated into a protein.
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    URL: http://dx.doi.org/10.1007/BF00020478
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    Genetic similarity among Arabidopsis thaliana ecotypes estimated by DNA sequence comparison (1996)
    Springer
    Plant molecular biology 32 (1996), S. 915-922 
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    ISSN: 1573-5028
    Keywords: Arabidopsis ; DNA sequence polymorphism ; ecotypes ; genetic similarity ; sequence comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA polymorphisms among Arabidopsis thaliana ecotypes are widely used as genetic markers in map-based cloning strategies. New PCR-based molecular markers do not only facilitate molecular mapping, but can also be used to obtain reliable sequence information for cladistic analyses. We have used CAPS (cleaved amplified polymorphic sequences) markers and a direct sequencing strategy to estimate genetic similarity among eighteen Arabidopsis ecotypes. Sequences at four loci, two from the nuclear and two from a non-nuclaar genome, were analysed. For each ecotype more than 1000pb of sequence information was obtained, and genetic similarity was calculated from a total of 35 polymorphic sites using a character-based approach. Divergence ranged from zero up to 50 discordant characters among the 72 characters defined by the polymorphisms. Separate calculations based on the nuclear and the non-nuclear sequences were performed and revealed a number of common features, including the existence of small clusters of very closely related ecotypes separated from each other by extensive sequence divergence. Our results provide information useful especially to investigators setting up crosses for chromosome landing strategies.
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    URL: http://dx.doi.org/10.1007/BF00020488
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    Identification of a light-regulated MYB gene from an Arabidopsis transcription factor gene collection (1996)
    Springer
    Plant molecular biology 32 (1996), S. 987-993 
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    ISSN: 1573-5028
    Keywords: Arabidopsis ; differential screening ; light-regulated gene expression ; MYB-related proteins ; transcription factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seven different MYB-related genes have been isolated from a genomic Arabidopsis library with probes based on MYB DNA-binding motifs. The predicted amino acid sequence of these genes showed high similarity in the MYB domain but outside this region virtually no similarities were found. The set of MYB-related genes was used to identify differentially expressed genes following the transfer of etiolated seedlings to light. This differential screen resulted in the selection of the ATM4 gene which is induced by light within one hour of exposure of etiolated or dark-adapted seedlings.
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    URL: http://dx.doi.org/10.1007/BF00020495
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    Role of ω-3 fatty acid desaturases in the regulation of the level of trienoic fatty acids during leaf cell maturation (1996)
    Springer
    Planta 199 (1996), S. 439-442 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; ω-3 fatty acid desaturase ; Leaf cell maturity ; Linolenic acid ; Lipid transfer ; Mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Trienoic fatty acids, namely α-linolenic acid and hexadecatrienoic acid, present in leaf lipids are produced by ω-3 fatty acid desaturases located in the endoplasmic reticulum and plastid membranes. The changes in the level of trienoic fatty acids during leaf maturation were investigated in wild-type plants of Arabidopsis thaliana (L.) Heynh. and in the fad7 mutant deficient in the activity of a plastid ω-3 desaturase. The levels of trienoic fatty acids increased in 26 °C- and 15 °C-grown wild-type plants with maturation of leaves. The increase in trienoic fatty acids was mainly due to galactolipids enriched in plastid membranes. In addition, the relative levels of trienoic fatty acids in major glycerolipids, including phospholipids enriched in the endoplasmic reticulum membranes, also increased with leaf maturation. By contrast, when the fad7 mutant was grown at 26 °C, the relative levels of trienoic fatty acids in individual lipids decreased with leaf maturation. The decreases in the levels of trienoic fatty acids, however, were alleviated when the fad7 mutant was grown at 15 °C. These results suggest that the plastid ω-3 desaturase plays a major role in increasing the levels of trienoic fatty acids with leaf maturation.
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    The role of calmodulin in the gravitropic response of the Arabidopsis thaliana agr-3 mutant (1996)
    Springer
    Planta 199 (1996), S. 343-351 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; Calmodulin ; Gravitropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Calmodulin, a primary plant calcium receptor, is known to be intimately involved with gravitropic sensing and transduction. Using the calmodulin-binding inhibitors trifluoperazine, W7 and calmidazolium, gravitropic curvature of Arabidopsis thaliana (L.) Heynh, ecotype Landsberg, roots was separable into two phases. Phase I was detected at very low concentrations (0.01 μM) of trifluoperazine and calmidazolium, did not involve growth changes, accounted for about half the total curvature of the root and may represent the specific contribution of the cap to gravity sensing. Phase II commenced around 1.0 μM and involved inhibition of both growth and curvature. The agr-3 mutant exhibited a reduced gravitropic response and was found to lack phase I curvature, suggesting that the mutation alters either use or expression of calmodulin. The sequences of wild-type and agr-3 calmodulin (CaM-1) cDNAs, which are root specific were completely determined and found to be identical. Upon gravitropic stimulation, wild-type Arabidopsis seedlings increased calmodulin mRNA levels by threefold in 0.5 h. On the other hand, gravitropic stimulation of agr-3 decreased calmodulin mRNA accumulation. The possible basis of the two phases of curvature is discussed and it is concluded that agr-3 has a lesion located in a general gravity transmission sequence, present in many root cells, which involves calmodulin mRNA accumulation.
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    URL: http://dx.doi.org/10.1007/BF00195725
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    Cytosolic ascorbate peroxidase from Arabidopsis thaliana L. is encoded by a small multigene family (1996)
    Springer
    Planta 198 (1996), S. 64-69 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; Ascorbate peroxidase (cytosolic, plastidial) ; Multigene family ; Oxidative stress ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A second cytosolic ascorbate peroxidase (cAPX; EC 1.11.1.11) gene from Arabidopsis thaliana has been characterised. This second gene (designated APX1b) maps to linkage group 3 and potentially encodes a cAPX as closely related to that from other dicotyledonous species as to the other member of this gene family (Kubo et al, 1993, FEBS Lett 315: 313–317; here designated APX1a), which maps to linkage group 1. In contrast, the lack of sequence similarity in non-coding regions of the genes implies that they are differentially regulated. Under non-stressed conditions only APX1a is expressed. APX1b was identified during low-stringency probing using a cDNA coding for pea cAPX which, in turn, was recovered from a cDNA library by immunoscreening with an antiserum raised against tea plastidial APX (pAPX). No pAPX cDNAs were recovered, despite the antiserum displaying specificity for pAPX in Western blots.
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    Intracellular magnetophoresis of amyloplasts and induction of root curvature (1996)
    Springer
    Planta 198 (1996), S. 87-94 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; Gravitropism ; High-gradient magnetic field ; Linum ; Root growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, ▽(H2/2), was about 109 Oe2 · cm−1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.
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    Chilling, oxidative stress and antioxidant responses inArabidopsis thaliana callus (1996)
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    Planta 198 (1996), S. 371-377 
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    ISSN: 1432-2048
    Keywords: Antioxidant enzymes ; Arabidopsis ; Chilling stress ; Glutathione ; Hydrogen peroxide ; Lipid peroxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chilling ofArabidopsis thaliana (L.) Heynh. callus tissue to 4 °C led to conditions of oxidative stress, as indicated by increased levels of the products of peroxidative damage to cell membranes. Cellular H2O2 was also observed to increase initially upon chilling but by day 8 cellular levels had declined to below control levels. Although levels of catalase activity remained similar to those in unchilled tissue, activity of ascorbate peroxidase increased between days 4 and 8 of chilling to 4 °C. In callus held at 23 °C, levels of reduced glutathione remained static whereas they rose in callus held at 4 °C. Levels of oxidised glutathione were initially low but increased significantly by day 4 in the chilled callus. At 23 °C, however, levels of oxidised glutathione remained low. Between days 1 and 3 at 4 °C, levels of glutathione reductase activity increased but by day 8 glutathione reductase activity was similar to that in cells held at 23 °C. Exposure of callus to abscisic acid at 23 °C also led to increased activities of ascorbate peroxidase and glutathione reductase.
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    Modification of reproductive development in Arabidopsis thaliana under spaceflight conditions (1996)
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    Planta 198 (1996), S. 588-594 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; Female gametophyte ; Pollen ; Reproduction ; Spaceflight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive development in Arabidopsis thaliana (L.) Heynh. cv. Columbia plants was investigated under spaceflight conditions on shuttle mission STS-51. Plants launched just prior to initiation of the reproductive phase developed flowers and siliques during the 10-d flight. Approximately 500 flowers were produced in total by the 12 plants in both the ground control and spaceflight material, and there was no significant difference in the number of flowers in each size class. The flower buds and siliques of the spaceflight plants were not morphologically different from the ground controls. Pollen viability tests immediately post-flight using fluorescein diacetate indicated that about 35% of the pollen was viable in the spaceflight material. Light-microscopy observations on this material showed that the female gametophytes also had developed normally to maturity. However, siliques from the spaceflight plants contained empty, shrunken ovules, and no evidence of pollen transfer to stigmatic papillae was found by light microscopy immediately post-flight or by scanning electron microscopy on fixed material. Short stamen length and indehiscent anthers were observed in the spaceflight material, and a film-like substance inside the anther that connected to the tapetum appeared to restrict the release of pollen from the anthers. These observations indicate that given appropriate growing conditions, early reproductive development in A. thaliana can occur normally under spaceflight conditions. On STS-51, reproductive development aborted due to obstacles in pollination or fertilization.
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    Isolation of high-chlorophyll-fluorescence mutants ofArabidopsis thaliana and their characterisation by spectroscopy, immunoblotting and Northern hybridisation (1996)
    Springer
    Planta 198 (1996), S. 385-396 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; High-chlorophyll-fluorescence mutants ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thirty-four recessive photosynthetic mutants of the high-chlorophyll-fluorescence (hcf) phenotype have been isolated by screening 7700 M2 progenies of ethyl methane sulfonate-treated seeds ofArabidopsis thaliana. Most of the mutants isolated were found to be seedlinglethal, but could be grown on sucrose-supplemented media. Chlorophyll (Chl) fluorescence induction, absorption changes in the reaction-centre chlorophyll of PS I (P700) at 830 nm and Chla/Chlb ratios were recorded in order to probe the photosynthetic functions and to define the mutational lesion. These studies were complemented by immunoblot and Northern analyses which finally led to the classification of the mutants into six different groups. Four classes of mutants were affected in PS I, PS II (two different classes) or the intersystem electron-transport chain, respectively. A fifth mutant class was of pleiotropic nature and the sixth class comprised a Chlb-deficient mutant. Several of the mutants showed severe deficiencies in the levels of subunits of PS I, PS II or the cytochromeb 6/f complex. Thus the mutational lesions could be located precisely. Only one mutant was defective in the transcript patterns of some plastid-encoded photosynthesis genes. Hence most of the mutants isolated appear to be affected in translational and post-translational regulatory processes of thylakoid membrane biogenesis or in structural genes encoding constituent subunits of the thylakoid protein complexes.
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    The 5′ untranslated region of Arabidopsis thaliana calmodulin cDNA is an independent cDNA containing an open reading frame (1996)
    Springer
    Planta 198 (1996), S. 162-163 
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    ISSN: 1432-2048
    Keywords: Arabidopsis ; Calmodulin cDNA (5′ untranslated region) ; Complementary DNA ; Open reading frame
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone, pAUK1, with an open reading frame (ORF) coding for a hypothetical 164-amino-acid protein was isolated from an Arabidopsis thaliana (L.) Heynh cDNA library. The clone was attached, tail to tail, to the 3′ end of A. thaliana hexokinase cDNA. An almost identical sequence had been previously described as the 5′ untranslated region (5′ UTR) of A. thaliana calmodulin cDNA (ACaM-2). Sequence comparison with three additional A. thaliana truncated cDNA clones which appear in a database (GenBank) supports the conclusion that pAUKl is identical to the 5′ UTR of ACaM-2 and that the 5′ UTR of ACaM-2 is an independent cDNA artificially linked to A. thaliana calmodulin cDNA.
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    Interaction of FLC and late-flowering mutations in Arabidopsis thaliana (1996)
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    Molecular genetics and genomics 251 (1996), S. 69-74 
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    ISSN: 1617-4623
    Keywords: Key words Flowering ; Arabidopsis ; Photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The phenotype caused by mutations that affect the timing of flowering in Arabidopsis thaliana has been most extensively analyzed in the Landsberg erecta (Ler) genetic background. In Ler, the late-flowering phenotype of FRIGIDA and mutations in LUMINIDEPENDENS is suppressed by the Ler allele of FLC. In this study, the interactions of nine mutations conferring late flowering with the FLC allele of the Columbia ecotype (FLC-Col), which does not suppress late flowering, were examined. The effect on flowering time of combining six of the mutations with FLC-Col was additive; plants containing FLC-Col with fd, gi, fwa, fha, ft, and fe flowered slightly later than plants containing these mutations with the Ler allele of FLC. In contrast, a synergistic effect was observed between FLC-Col and three mutations; fca, fpa, and fve plants became extremely late flowering when combined with FLC-Col. Maximum delay in flowering for the majority of the mutant strains required FLC-Col in a homozygous state, although for fpa and fe a single copy of FLC-Col allowed maximum lateness. In addition, the fd and fe mutations became more dominant in the presence of FLC-Col.
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    Correlation of nonanucleotide motifs with transcript initiation of 18S rRNA genes in mitochondria of pea, potato and Arabidopsis (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 429-436 
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    ISSN: 1617-4623
    Keywords: Key words 18S rRNA transcription ; Plant mitochondrial promoters ; Arabidopsis ; Pea ; Potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Transcription initiation sites for the mitochondrial 18S rRNA genes in the dicot plants Arabidopsis thaliana, potato and pea were identified by a combination of in vitro capping, primer extension and S-1 analyses. These promoters contain a nonanucleotide motif and an AT-rich sequence similar to many mRNA and tRNA promoters in dicot mitochondria. In Arabidopsis and potato, active promoters are located within 120 nucleotides upstream of the 18S rRNA genes, as in Oenothera. The nucleotide sequence in the corresponding region in pea mitochondria is well conserved, but is not used as promoter in this plant. Instead a novel promoter sequence is used that lies several hundred nucleotides upstream. These results show that rRNAs can be transcribed from the same promoter types as mRNAs and tRNAs in plant mitochondria. However, the sequence features presently attributed to plant mitochondrial promoters – the conserved nonanucleotide and the upstream AT-rich box – do not allow to deduce the presence of an active promoter from genomic sequence data alone.
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    Novel structure of a high molecular weight FK506 binding protein fromArabidopsis thaliana (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 510-517 
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    ISSN: 1617-4623
    Keywords: FK506 binding protein (FKBP) ; Immunophilins ; Tetratricopeptide repeat (TPR) ; Plant stress ; Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated clones of an Arabidopsis gene (ROF1, forrotamaseFKBP) encoding a high molecular weight member of the FK506 binding protein (FKBP) family. The deduced amino acid sequence of ROF1 predicts a 551-amino acid, 62 kDa polypeptide which is 44% identical to human FKBP59 — a 59 kDa FKBP which binds to the 90 kDa heat shock protein and is associated with inactive steroid hormone receptors. ROF1 contains three FKBP12-like domains in the N-terminal portion of the protein (in contrast to two domains in mammalian FKBP59), an internal repeat structure associated with protein-protein interactions (tetratricopeptide repeats), and a putative calmodulin binding domain near the C-terminal region of the protein. No sequences associated with protein translocation out of the cytosol were found in ROF1.ROF1 mRNA was found at equivalent low levels in light-grown roots, stems, and flowers and at slightly higher levels in leaves. The abundance ofROF1 mRNA increased several-fold under stress conditions such as wounding or exposure to elevated NaCl levels.
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    Molecular analysis of theArabidopsis pattern formation geneGNOM: gene structure and intragenic complementation (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 681-691 
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    ISSN: 1617-4623
    Keywords: Arabidopsis ; GNOM gene ; Intragenic complementation ; Conserved regions ; YeastYEC2 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TheGNOM gene is required for pattern formation along the main body axis of the embryo in the flowering plantArabidopsis thaliana. Mutations in theGNOM gene alter the asymmetric division of the zygote and interfere with the formation of distinct apical-basal regions in the developing embryo. We have isolated theGNOM gene by positional cloning, characterised its structure and determined the molecular lesions in mutant alleles. Although the predicted 163 kDa GNOM protein has a conserved domain in common with the yeast secretory protein Sec7p, it is most closely related in size and overall similarity to the product of the yeastYEC2 gene, which is not essential for cell viability. Four fully complementinggnom alleles carry missense mutations in conserved regions, seven partially complementing alleles have premature stop codon mutations and two non-complementing alleles have splice-site lesions. Our results suggest that the GNOM protein acts as a complex of identical subunits and that partial complementation may involve low levels of full-length protein generated by inefficient translational read-through.
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    Dynamics of vegetative cytoplasm during generative cell formation and pollen maturation inArabidopsis thaliana (1996)
    Springer
    Protoplasma 194 (1996), S. 81-90 
    Details
    ISSN: 1615-6102
    Keywords: Arabidopsis ; Pollen ; Vegetative cytoplasm ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural changes of pollen cytoplasm during generative cell formation and pollen maturation inArabidopsis thaliana were studied. The pollen cytoplasm develops a complicated ultra-structure and changes dramatically during these stages. Lipid droplets increase after generative cell formation and their organization and distribution change with the developmental stage. Starch grains in amyloplasts increase in number and size during generative and sperm cell formation and decrease at pollen maturity. The shape and membrane system of mitochondria change only slightly. Dictyo-somes become very prominent, and numerous associated vesicles are observed during and after sperm cell formation. Endoplasmic reticulum appears extensively as stacks during sperm cell formation. Free and polyribosomes are abundant in the cytoplasm at all developmental stages although they appear denser at certain stages and in some areas. In mature pollen, all organelles are randomly distributed throughout the vegetative cytoplasm and numerous small particles appear. Organization and distribution of storage substances and appearance of these small particles during generative and sperm cell formation and pollen maturation are discussed.
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    Consistent handedness of microtubule helical arrays in maize and Arabidopsis primary roots (1996)
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    Protoplasma 190 (1996), S. 8-15 
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    ISSN: 1615-6102
    Keywords: Arabidopsis ; Handedness ; Helical array ; Maize ; Microtubule organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The orientation of cortical microtubules in plant cells has been extensively studied, in part because of their influence on the expansion of most plant cell types. Cortical microtubules are often arranged in helical arrays, which are well known to occur with a specific pitch as a function of development or experimental treatment; however, it is not known if the handedness of helical arrays can also be specified. We have studied the handedness of helical arrays by using Vibratome sectioning of maize primary roots and confocal microscopy of Arabidopsis primary roots. In cortical cells of maize roots, the helical array was found to have the same handedness at a given position, not only for the cells of a single root, but also for the cells of more than one hundred roots examined. Quantification of angular distribution of apparent individual microtubules showed that defined regions of the root were composed of cells with highly uniform microtubule orientation. In the region between transverse and longitudinal microtubules (5–10.5 mm from the tip), the array formed a right-handed helix, and basal of cells with longitudinal microtubules (11.5–15 mm from the tip), the array formed a left-handed helix. Similarly, in epidermal cells of Arabidopsis roots right-handed helical arrays were found in the region between transverse and longitudinal microtubules. These results suggest that, in addition to the orientation of microtubules, the handedness of helical microtubule arrays is under cellular control.
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    Root apical organization inArabidopsis thaliana 1. Root cap and protoderm (1996)
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    Protoplasma 192 (1996), S. 178-188 
    Details
    ISSN: 1615-6102
    Keywords: Arabidopsis ; Root apical meristem development ; Dermatogen/calyptrogen histogen ; Spiral pattern ; Root cap ; Protoderm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the development of the root cap and protoderm inArabidopsis thaliana root tips.A. Thaliana roots have closed apical organization with the peripheral root cap, columella root cap and protoderm developing from the dermatogen/calyptrogen histogen. The columella root cap arises from columella initials. The initials for the peripheral root cap and protoderm are arranged in a collar and the initiation event for these cells occurs in a sequential pattern that is coordinated with the columella initials. The resulting root cap appears as a series of interconnected spiraling cones. The protoderm, in three-dimensions, is a cylinder composed of cell files made up of packets of cells. The number of cell files within the protoderm cylinder increases as the root ages from one to two weeks. The coordinated division sequence of the dermatogen/calyptrogen and the increase in the number of protoderm cell files are both features of post-embryonic development within the primary root meristem.
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    Are the phytochromes protein kinases? (1996)
    Springer
    Protoplasma 195 (1996), S. 12-17 
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    ISSN: 1615-6102
    Keywords: Protein histidine kinases ; Two-component systems ; Sensory photoreceptors ; Site-directed mutagenesis ; Arabidopsis ; Transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The biochemical mechanism of phytochrome action is unknown. We have examined the proposal, based on sequence similarities to the sensor histidine kinase components of bacterial two-component signaling systems, that the phytochromes may be functional homologs of these kinases. Four amino acids, three highly conserved between the phytochrome and bacterial kinase molecules and the other, the histidine residue putatively the target of autophosphorylation, were changed singly in the oat phytochrome A sequence by in vitro site-directed mutagenesis, and the resultant mutant photo-receptor molecules were assayed for activity by overexpression in transgenic Arabidopsis. Three of the four mutant molecules retained activity equivalent to that of the unmutagenized parent sequence, whereas the fourth mutant could not be evaluated because of low expression. The data show that the former three mutagenized residues are not essential for phytochrome A function in transgenic Arabidopsis, but, because of the negative nature of the results, the possibility cannot be precluded that the photoreceptor functions as a protein kinase independent of these residues.
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    Interaction ofFLC and late-flowering mutations inArabidopsis thaliana (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 69-74 
    Details
    ISSN: 1617-4623
    Keywords: Flowering ; Arabidopsis ; Photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phenotype caused by mutations that affect the timing of flowering inArabidopsis thaliana has been most extensively analyzed in the Landsbergerecta (Ler) genetic background. In Ler, the late-flowering phenotype ofFRIGIDA and mutations inLUMINIDEPENDENS is suppressed by the Ler allele ofFLC. In this study, the interactions of nine mutations conferring late flowering with theFLC allele of the Columbia ecotype (FLC-Col), which does not suppress late flowering, were examined. The effect on flowering time of combining six of the mutations withFLC-Col was additive; plants containingFLC-Col withfd, gi, fwa, fha, ft, andfe flowered slightly later than plants containing these mutations with theLer allele ofFLC. In contrast, a synergistic effect was observed betweenFLC-Col and three mutations;fca, fpa, andfve plants became extremely late flowering when combined withFLC-Col. Maximum delay in flowering for the majority of the mutant strains requiredFLC-Col in a homozygous state, although forfpa andfe a single copy ofFLC-Col allowed maximum lateness. In addition, thefd andfe mutations became more dominant in the presence ofFLC-Col.
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    URL: http://dx.doi.org/10.1007/BF02174346
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    Complementation of anArabidopsis thaliana biotin auxotroph with anEscherichia coli biotin biosynthetic gene (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 261-266 
    Details
    ISSN: 1617-4623
    Keywords: Biotin ; Arabidopsis ; Complementation ; bioA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TheArabidopsis thaliana biotin auxotrophbio1 was rendered prototrophic by transformation with a chimeric transgene containing theEscherichia coli bioA gene driven by a constitutive promoter. ThebioA gene encodes the biotin biosynthetic enzyme 7,8-diaminopelargonic acid aminotransferase. Unlike the untransformed control plants, transgenic plants expressing the bacterial transgene synthesized biotin and grew to maturity without biotin-deficiency symptoms. These findings demonstrate thatbio1/bio1 mutant plants are defective in the gene encoding 7,8-diaminopelargonic acid aminotransferase.
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    URL: http://dx.doi.org/10.1007/BF02172516
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    A novel repetitive sequence associated with the centromeric regions of Arabidopsis thaliana chromosomes (1996)
    Springer
    Molecular genetics and genomics 253 (1996), S. 247-252 
    Details
    ISSN: 1617-4623
    Keywords: Key words Middle repetitive sequence ; Arabidopsis ; In situ hybridization ; Centromere ; Physical mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The middle repetitive fraction of the Arabidopsis genome has been relatively poorly characterized. We describe here a novel repetitive sequence cloned in the plasmid mi167, and present in ∼90 copies in the genome of Arabidopsis thaliana ecotype Columbia. Hybridization analysis to physically mapped YAC clones representing Arabidopsis chromosome 4 revealed four mi167-hybridizing loci, all clustered near the centromere. No other loci were detected on YAC clones covering chromosome 4. In situ hybridisation experiments to Arabidopsis chromosome spreads showed that mi167-hybridizing sequences are clustered at the centromeric heterochromatin of all five chromosomes; on two chromosomes the hybridization appeared to be localised on one arm. Additional mi167-hybridizing loci were detected, one of which was adjacent to a non-centromeric, heterochromatic region. This work supports the idea that the majority of middle repetitive DNA in the Arabidopsis genome is clustered. It also adds to our understanding of the organization of the centromere of Arabidopsis chromosome 4.
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    URL: http://dx.doi.org/10.1007/s004380050319
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  • 41
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    Correlation of nonanucleotide motifs with transcript initiation of 18S rRNA genes in mitochondria of pea, potato andArabidopsis (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 429-436 
    Details
    ISSN: 1617-4623
    Keywords: 18S rRNA transcription ; Plant mitochondrial promoters ; Arabidopsis ; Pea ; Potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcription initiation sites for the mitochondrial 18S rRNA genes in the dicot plantsArabidopsis thaliana, potato and pea were identified by a combination of in vitro capping, primer extension and S-1 analyses. These promoters contain a nonanucleotide motif and an AT-rich sequence similar to many mRNA and tRNA promoters in dicot mitochondria. InArabidopsis and potato, active promoters are located within 120 nucleotides upstream of the 18S rRNA genes, as inOenothera. The nucleotide sequence in the corresponding region in pea mitochondria is well conserved, but is not used as promoter in this plant. Instead a novel promoter sequence is used that lies several hundred nucleotides upstream. These results show that rRNAs can be transcribed from the same promoter types as mRNAs and tRNAs in plant mitochondria. However, the sequence features presently attributed to plant mitochondrial promoters — the conserved nonanucleotide and the upstream AT-rich box — do not allow to deduce the presence of an active promoter from genomic sequence data alone.
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    URL: http://dx.doi.org/10.1007/BF02173008
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  • 42
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    Complementation of an Arabidopsis thaliana biotin auxotroph with an Escherichia coli biotin biosynthetic gene (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 261-266 
    Details
    ISSN: 1617-4623
    Keywords: Key words Biotin ; Arabidopsis ; Complementation ; bioA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The Arabidopsis thaliana biotin auxotroph bio1 was rendered prototrophic by transformation with a chimeric transgene containing the Escherichia coli bioA gene driven by a constitutive promoter. The bioA gene encodes the biotin biosynthetic enzyme 7,8-diaminopelargonic acid aminotransferase. Unlike the untransformed control plants, transgenic plants expressing the bacterial transgene synthesized biotin and grew to maturity without biotin-deficiency symptoms. These findings demonstrate that bio1/bio1 mutant plants are defective in the gene encoding 7,8-diaminopelargonic acid aminotransferase.
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    URL: http://dx.doi.org/10.1007/BF02172516
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    The KEULE gene is involved in cytokinesis in Arabidopsis (1996)
    Springer
    Molecular genetics and genomics 253 (1996), S. 267-277 
    Details
    ISSN: 1617-4623
    Keywords: Key words KEULE ; Cytokinesis ; Arabidopsis ; Multinucleate cells ; Wall stubs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We present evidence to show that the KEULE gene of Arabidopsis is involved in cytokinesis. Mutant keule embryos have large multinucleate cells with gapped or incomplete cross walls, as well as cell wall stubs that are very similar to those observed upon caffeine inhibition of cytokinesis in plants. These defects are observed in all populations of dividing cells in the mutant, including calli, but less frequently in mature cells. Cell division appears to be slowed down, and the planes of cell division are often misoriented. In late embryos and seedlings, cross-wall formation usually appears complete, suggesting that the requirement for KEULE during cytokinesis is not absolute. Nonetheless, keule mutants die as seedlings with large polyploid cells. The bloated surface layer of keule seedlings does not uniformly behave like wild-type epidermis, and patches of this layer assume characteristics of the underlying ground tissue. The cytokinesis defect of keule mutants may influence aspects of cellular differentiation.
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    URL: http://dx.doi.org/10.1007/PL00008594
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    Novel structure of a high molecular weight FK506 binding protein from Arabidopsis thaliana (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 510-517 
    Details
    ISSN: 1617-4623
    Keywords: Key words FK506 binding protein (FKBP) ; Immunophilins ; Tetratricopeptide repeat (TPR) ; Plant stress ; Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have isolated clones of an Arabidopsis gene (ROF1, for rotamase FKBP) encoding a high molecular weight member of the FK506 binding protein (FKBP) family. The deduced amino acid sequence of ROF1 predicts a 551-amino acid, 62 kDa polypeptide which is 44% identical to human FKBP59 – a 59 kDa FKBP which binds to the 90 kDa heat shock protein and is associated with inactive steroid hormone receptors. ROF1 contains three FKBP12-like domains in the N-terminal portion of the protein (in contrast to two domains in mammalian FKBP59), an internal repeat structure associated with protein-protein interactions (tetratricopeptide repeats), and a putative calmodulin binding domain near the C-terminal region of the protein. No sequences associated with protein translocation out of the cytosol were found in ROF1. ROF1 mRNA was found at equivalent low levels in light-grown roots, stems, and flowers and at slightly higher levels in leaves. The abundance of ROF1 mRNA increased several-fold under stress conditions such as wounding or exposure to elevated NaCl levels.
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    URL: http://dx.doi.org/10.1007/BF02172397
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    Root apical organization inArabidopsis thaliana ecotype ‘WS’ and a comment on root cap structure (1996)
    Springer
    Plant and soil 187 (1996), S. 91-95 
    Details
    ISSN: 1573-5036
    Keywords: Arabidopsis ; histogems ; root apical meristem ; root cap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Arabidopsis thaliana roots have closed apical organization with three initial tiers. The dermatogen/calyptrogen tier consists of two parts-the central initials form the columella root cap, and the peripheral initial cells form the protoderm (epidermis) and the peripheral root cap. These peripheral initials divide in a sequence to form a root cap consisting of interconnected cones. the periblem initial tier forms the ground meristem (cortex). For the first week after germination the periblem consists of one layer of initial cells. The peripheral cells of the tier divide periclinally and then anticlinally (a T-division) to form the two-layered cortex (outer cortex and endodermis). After about one week, all the peripheral cells have divided periclinally forming two initials; the outermost produces the outer cortex while the inner initial produces the endodermis and middle cortex layer. The latter two cells arise via a periclinal division. During this time, other cells within the tier divide periclinally to form a two-layered tier. The plerome forms the cells of the procambium (vascular cylinder) by simple anticlinal divisions followed by longitudinal divisions to fill out the cell files of the vascular cylinder. A survey (27 dicot species in 17 families) of roots with closed apical organization revealed that there are three different types of root cap-concentric cylinders of cells (e.g.Linum), interconnecting cones (e.g.Arabidopsis) or overlapping arcs (e.g.Gossypium). H Lambers Section editor
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    URL: http://dx.doi.org/10.1007/BF00011660
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    Mutational analysis of root initiation in theArabidopsis embryo (1996)
    Springer
    Plant and soil 187 (1996), S. 1-9 
    Details
    ISSN: 1573-5036
    Keywords: Arabidopsis ; cell axialization ; embryo ; root ; vascular tissues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In dicotyledonous plants, primordia of most seedling organs are laid down between fertilization and the formation of the heart-stage embryo. InArabidopsis embryogenesis, highly regular cell divisions and cell expansions facilitate the characterization of mutant development. We have taken a genetic approach to identify genes involved in organising the hypocotyl/root axis. The initiation of this axis is marked by oriented expansions and longitudinal division of cells in the lower tier of the early globular embryo. These cells go on to form a defined number of parallel cell files that constitute the hypocotyl and most of the radicle. Mutants impaired in the initiation or elaboration of the hypocotyl/root axis were selected by their seedling phenotype and subsequently analysed at embryonic stages. Several conclusions are suggested by the phenotypes of these mutants. First, hypocotyl/root axis formation can be genetically separated from other aspects of embryonic pattern formation. Second, initiation of the hypocotyl/root axis appears to be genetically distinct from post-embryonic root initiation. Third, four loci were identified that appear to contribute to the elaboration of the axial pattern. Finally, an anatomical inspection of one of the mutants, amenable to an analysis at post-embryonic stages, suggests a genetic link between basal pattern formation in the embryo and aspects of vascular differentiation in the adult plant. H Lambers Section editor
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    URL: http://dx.doi.org/10.1007/BF00011652
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    Ethylene binding sites in higher plants (1996)
    Springer
    Plant growth regulation 18 (1996), S. 71-77 
    Details
    ISSN: 1573-5087
    Keywords: Arabidopsis ; ethylene ; ethylene binding protein ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A review of work carried out on ethylene binding in higher plants is presented. The use of radio-labelled displacement assays has identified specific 14C-ethylene binding in all tissues so far studied. virtually all higher plants studied contain at least two classes of ethylene binding site, one of which fully associates and dissociates in about 2 h and a class of sites that takes up to 20 h to become fully saturated. Although the types of site differ in their rate constants of association they have similar and high affinities for ethylene. A series of Arabidopsis thaliana mutants shown to vary in sensitivity to ethylene have been analysed for 14C-ethylene binding. One mutant, eti 5, which was shown to be unaffected by ethylene concentrations of up to 10,000 μL L−1 was also shown to exhibit reduced binding. In vivo and in vitro studies on pea have shown that ethylene binding can be detected in this tissue. In vitro studies have shown that both membrane and cytosolic fractions contain measurable amounts of ethylene binding. Interestingly, cytosolic ethylene binding consisted only of the fast associating/dissociating type. Developing cotyledons of Phaseolus vulgaris contain a higher concentration of ethylene binding sites that other tissues and only contain the slow dissociating component. These facets have allowed the purification of ethylene binding protein(s) (EBP) from this tissue. The proteins which bind ethylene can be resolved into two bands of 26 and 28 kDa on semi-denaturing PAGE and the proteins appear to be single entities on a 2-D gels. Data will be presented which indicate a possible role for heterotrimetric G-proteins in the early stages of the ethylene signal transduction pathway.
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    URL: http://dx.doi.org/10.1007/BF00028490
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    DNA regions flanking the major Arabidopsis thaliana satellite are principally enriched in Athila retroelement sequences (1996)
    Springer
    Genetica 97 (1996), S. 141-151 
    Details
    ISSN: 1573-6857
    Keywords: Arabidopsis ; heterochromatin ; retroviral element ; satellite DNA ; transposon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An analysis of Arabidopsis thaliana heterochromatic regions revealed that genomic sequences immediately flanking the major 180 bp satellite are essentially made of middle repetitive sequences and that most of these sequences correspond to defective Athila retroelements. Using YAC and λ clones, we evaluated the distribution of Athila elements in the Arabidopsis genome and showed that, despite the presence of numerous euchromatic copies, these elements are especially concentrated in or near heterochromatic regions. Sequencing of the various DNA transitions between satellite and Athila repeats provides strong evidence that most of the heterochromatic elements retrotransposed directly into 180 bp satellite clusters.
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    URL: http://dx.doi.org/10.1007/BF00054621
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    Experimental and genetic analysis of root development inArabidopsis thaliana (1996)
    Springer
    Plant and soil 187 (1996), S. 97-105 
    Details
    ISSN: 1573-5036
    Keywords: Arabidopsis ; cell fate ; embryogenesis ; laser ablation ; root meristem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The cellular organisation of theArabidopsis thaliana root is remarkably regular. A fate map of the primary root and root meristem that predicts the developmental destinies of cells within the embryonic root primordium has been constructed. Nevertheless, laser ablation experiments demonstrate that root meristem cells develop according to position and not according to lineage. Mutational analysis has identified genes required for cell specification in the radial as well as in the apical-basal dimension. The corresponding gene functions appear to be necessary during embryogenesis for the formation of a correctly patterned primary root. H Lambers Section editor
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    URL: http://dx.doi.org/10.1007/BF00011661
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    Studies on the possible role of protein phosphorylation in the transduction of the ethylene signal (1996)
    Springer
    Plant growth regulation 18 (1996), S. 135-141 
    Details
    ISSN: 1573-5087
    Keywords: Arabidopsis ; EBP ; ethylene ; phosphorylation ; receptors ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Previous work in our laboratory has demonstrated the existence of high affinity binding sites for the plant growth regulator ethylene. The ethylene binding protein (EBP), from Phaseolus cotyledons, shows many of the characteristics of a functional receptor for ethylene, has been purified on SDS-PAGE and polyclonal antibodies raised in rabbits. Current work involves the investigation of the ethylene transduction signal in a number of ethylene-responsive tissues. In peas, it has been shown that ethylene promotes the phosphorylation of specific proteins of similar molecular weight to the EBP from Phaseolus. Such ethylene-induced phosphorylation can be inhibited by the ethylene antagonist, 2,5-NBD. The antibodies raised to the EBP from Phaseolus have been shown to immunoprecipitate 32P-labelled proteins from membrane protein preparations obtained from pea tissue. Studies on ethylene binding in pea have also shown that the binding of ethylene may be regulated by phosphorylation. Thus, under conditions which promote phosphorylation, binding is inhibited, whereas the reverse is true under conditions which enhance dephosphorylation. Further work is described which examines the effect of protein kinase, protein phosphatase and calcium channel inhibitors on ethylene-induced phosphorylation in peas, together with wild-type (WT) and ethylene insensitive (eti) mutants of Arabidopsis thaliana. The effects of these treatments can be monitored in vivo using the ethylene-induced triple response as a screen. Furthermore, the protein profiles of such treated seedlings can then be compared by labelling protein extracts with 32P and subjecting the samples to SDS-PAGE followed by autoradiography.
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    URL: http://dx.doi.org/10.1007/BF00028498
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