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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The regular arrangement of leaves around a plant's stem, called phyllotaxis, has for centuries attracted the attention of philosophers, mathematicians and natural scientists; however, to date, studies of phyllotaxis have been largely theoretical. Leaves and flowers are formed from the shoot ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Key words: Cell wall ; Expansin ; Leaf development ; Lycopersicon (morphogenesis) ; Morphogenesis ; Shoot apex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Our previous work has shown that localised activity of the cell-wall-loosening protein expansin is sufficient to induce primordia on the apical meristem of tomato, consistent with the hypothesis that tissue expansion plays a key role in leaf initiation. In this paper we describe the earliest morphogenic events visible on the surface of the apical meristem of tomato (Lycopersicon esculentum Mill.) following treatment with expansin and report on the spectrum of final structures formed. Our observations are consistent with a proposed primary function of expansin effecting morphogenesis via altered biophysical stress patterns in the meristem. The primordia induced by expansin do not complete the full program of leaf development. We present data indicating that one reason for this might be the inability of exogenous expansin to mimic the endogenous pattern of expansin activity in the meristem. These data provide the first detailed analysis at the cellular level of expansin action on living tissue, the first description of the spectrum of structures induced by expansin on the apical meristem, and give an insight into a potentially fundamental mechanism in plant development.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 25 (1994), S. 319-321 
    ISSN: 1573-5028
    Keywords: tobacco ; transcription factor ; MADS box ; ubiquitous expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments in Antirrinum majus, Arabidopsis thaliana and Petunia hybrida have demonstrated that putative transcription factors of the so-called MADS-box family play an important role in determining floral organ identity. Such regulatory genes are transiently expressed in small numbers of cells in the floral apex. Here we describe the isolation of a cDNA from Nicotiana tabacum coding for a MADS-box protein which is expressed in both the floral and vegetative organs of the plant.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 35 (1997), S. 355-365 
    ISSN: 1573-5028
    Keywords: aldehyde dehydrogenase ; cytoplasmic male sterility ; fermentation ; glyoxylate cycle ; pollen ; tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acetaldehyde is one of the intermediate products of ethanolic fermentation, which can be reduced to ethanol by alcohol dehydrogenase (ADH). Alternatively, acetaldehyde can be oxidized to acetate by aldehyde dehydrogenase (ALDH) and subsequently converted to acetyl-CoA by acetyl-CoA synthetase (ACS). To study the expression of ALDHs in plants we isolated and characterized a cDNA coding for a putative mitochondrial ALDH (TobAldh2A) in Nicotiana tabacum/. TobALDH2A shows 54–60% identity at the amino acid level with other ALDHs and shows 76% identity with maize Rf2, a gene involved in restoration of male fertility in cms-T maize. TobAldh2A transcripts and protein were present at high levels in the male and female reproductive tissues. Expression in vegetative tissues was much lower and no induction by anaerobic incubation was observed. This suggests that TobALDH expression is not part of the anaerobic response, but may have another function. The use of specific inhibitors of ALDH and the pyruvate dehydrogenase (PDH) complex indicates that ALDH activity is important for pollen tube growth, and thus may have a function in biosynthesis or energy production.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 35 (1997), S. 343-354 
    ISSN: 1573-5028
    Keywords: acetaldehyde ; alcohol dehydrogenase ; cytoplasmic male sterility ; fermentation ; pollen ; pyruvate decarboxylase ; tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vegetative organs of plants, the metabolic switch from respiration to fermentation is dictated by oxygen availability. The two genes dedicated to ethanolic fermentation, pyruvate decarboxylase and alcohol dehydrogenase, are induced by oxygen deprivation and the gene products are active under oxygen stress. In pollen, these two genes are expressed in a stage-specific manner and transcripts accumulate to high levels, irrespective of oxygen availability. We have examined the expression pattern of pyruvate decarboxylase and alcohol dehydrogenase at the protein level in developing pollen and show that the active proteins are localized to the gametophytic tissue and begin to accumulate at microspore mitosis. A flux through the ethanolic fermentation pathway could already be detected very early in pollen development, occurring in all stages from premeiotic buds to mature pollen. This flux was primarily controlled not by oxygen availability, but rather by sugar supply. At a high rate of sugar metabolism, respiration and fermentation took place concurrently in developing and germinating pollen. We propose that aerobic fermentation provides a shunt from pyruvate to acetyl-CoA to accommodate the increased demand for energy and biosynthetic intermediates during pollen development and germination. A possible undesirable side-effect is the potential accumulation of toxic acetaldehyde. Our results support a model for cms-T-type male sterility in maize, in which degeneration of the tapetum is caused by the toxic effects of acetaldehyde on mitochondria weakened by the presence of the URF13 protein.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5028
    Keywords: cell size ; constitutive gene expression ; histochemistry ; in situ hybridization ; shoot apical meristem ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The NeIF-4A10 gene belongs to a family of at least ten genes, all of which encode closely related isoforms of translation initiation factor 4A. The promoter region of NeIF-4A10 was sequenced, and four mRNA 5′ ends were determined. Deletions containing 2750, 689 and 188 bp of untranscribed upstream DNA were fused to the GUS reporter gene and introduced into transgenic tobacco. The three constructs mediated GUS expression in all cells of the leaf, stem and shoot apical meristem. Control experiments using in situ hybridization and tissue printing indicated that the observed GUS expression matches the expression patterns of NeIF-4A mRNA and protein. This detailed analysis at the level of mRNA, protein and reporter gene expression shows that NeIF-4A10 is an ideal constitutively expressed control gene. We argue that inclusion of such a control gene in experiments dealing with specifically expressed genes is in many cases essential for the correct interpretation of observed expression patterns.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 28 (1995), S. 739-750 
    ISSN: 1573-5028
    Keywords: alcohol dehydrogenase ; fermentation ; gene expression ; pollen ; pyruvate decarboxylase ; respiration ; tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We characterized the genes coding for the two dedicated enzymes of ethanolic fermentation, alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), and show that they are functional in pollen. Two PDC-encoding genes were isolated, which displayed reciprocal regulation: PDC1 was anaerobically induced in leaves, whereas PDC2 mRNA was absent in leaves, but constitutively present in pollen. A flux through the ethanolic fermentation pathway could be measured in pollen under all tested environmental and developmental conditions. Surprisingly, the major factor influencing the rate of ethanol production was not oxygen availability, but the composition of the incubation medium. Under optimal conditions for pollen tube growth, approximately two-thirds of the carbon consumed was fermented, and ethanol accumulated into the surrounding medium to a concentration exceeding 100 mM.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 26 (1994), S. 1747-1757 
    ISSN: 1573-5028
    Keywords: cDNA gene family ; NeIF-4A ; RNA helicase ; translation initiation factor ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Characterization of cDNAs encoding eukaryotic translation initiation factor 4A (eIF-4A) indicates the expression of a minimum of ten related genes in tobacco leaf cells. The ten groups fall into two gene families, NeIF-4A2 and NeIF-4A3. The majority of the cDNAs exhibit significant sequence similarity to the NeIF-4A2 family at both the DNA and deduced amino acid levels. Northern analysis using specific probes indicates variable expression of four family members in various tobacco organs. Western analysis, using an anti-tobacco eIF-4A polyclonal antibody, reveals a complex pattern of immunologically related polypeptides of approximately 46 kDa. Subcellular fractionation suggests that at least one eIF-4A-related polypeptide is located in the chloroplast where it is ribosome-associated.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 27 (1995), S. 637-649 
    ISSN: 1573-5028
    Keywords: eIF-4A ; DEAD-box ; translation initiation ; pollen-specific ; microspore mitosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A pollen-specific sequence, NeIF-4A8, has been isolated from a cDNA library from mature pollen of Nicotiana tabacum cv. Samsun. NeIF-4A8 is a full-length cDNA whose deduced amino acid sequence exhibits high homology to the eucaryotic translation initiation factor eIF-4A from mouse, Drosophila and tobacco. eIF-4A is an RNA helicase which belongs to the supergene family of DEAD-box proteins. Northern blot analysis with a gene-specific probe showed strict anther-specific expression of NeIF-4A8 starting at microspore mitosis. With antibodies raised against tobacco eIF-4A the presence of abundant eIF-4A-related proteins in developing anthers and pollen grains was demonstrated. The genomic analysis shows that the coding region is split by three introns whereas a large, fourth intron is situated in the 5′-untranslated region. A promoter construct with 2137 bp of upstream sequence fused to the GUS reporter gene was used to confirm that the expression is confined to the haploid cells within the anther. NeIF-4A8 is a prime candidate for mediating translational control in the developing male gametophyte.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 178 (1996), S. 75-82 
    ISSN: 1573-5036
    Keywords: cold acclimation ; ecophysiology ; fermentation ; flooding ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acorus calamus L is an amphibious plant, which is exposed to periods of flooding and consequently hypoxic conditions as a part of its natural life cycle. Previous experiments under laboratory conditions have shown that the plant can survive for two months in the complete absence of oxygen, and that during this period the expression of genes encoding the glycolytic enzymes fructose-1,6-bisphosphate aldolase (ALD), pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) is induced in leaves and rhizomes (Bucher and Kuhlemeier, 1993). Here we studied the expression of ALD and ADH through two years in the natural habitat of A. calamus. Under natural conditions roots and rhizomes were always submerged but newly grown leaves emerged in spring; in autumn the leaves senesced and the whole plant was submerged again. High Ald and Adh mRNA levels in leaf and rhizome were found only in winter when the leaves were entirely submerged. Upon leaf emergence in spring the mRNA levels rapidly declined. Under controlled experimental conditions expression of Ald and Adh was not induced by low temperature. The combination of laboratory and field experiments supports the hypothesis that oxygen deprivation rather than low temperature is a major regulator of glycolytic gene expression in A. calamus. The possible role of other environmental factors is also discussed.
    Type of Medium: Electronic Resource
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