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  • 1
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Somatic embryogenesis ; Gene expression ; Heat shock protein ; Picea ; Polyethylene glycol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three cDNAs (PgEMB22, 27 and 29) predicted to encode low-molecular-weight (LMW) heat-shock proteins (HSPs) were cloned and characterized from white spruce [Picea glauca (Moench) Voss] somatic embryo tissues by differentially screening a cotyledonary embryo cDNA library. Clone PgEMB22 is predicted to encode a putative mitochondria-localized LMW HSP, and PgEMB27 and 29 are predicted to encode different cytoplasmic class II LMW HSPs, although they share 84.7% identity within DNA coding regions and 83.0% identity for predicted proteins. They are developmentally regulated during somatic embryo development and subsequent embryo germination, in addition they show strong response to heat-shock stress. Transcripts of the two kinds of hsp genes could be detected in embryogenic tissues before induction of embryo maturation, but subsequently increased, being most abundant at late embryo stages. Gene expression levels were very low or not detectable in germinated plantlets or needle tissues from older plants. Abscisic acid and polyethylene glycol, stimulators for spruce embryo maturation, could also induce the hsp genes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Endochitinase ; Fungal elicitation ; β-1,3-Glucanase ; Picea glauca ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two cDNAs isolated from white spruce [Picea glauca (Moench) Voss] somatic embryos, are predicted to encode a basic class IV chitinase and a β-1,3-glucanase, respectively corresponding to genesPgChi-1 andPgGlu-1. Each represents a multigene family in spruce. Transcripts homologous toPgChi-1 orPgGlu-1 genes were highly abundant in embryogenic tissues and gradually decreased after tissues were placed on abscisic acid-containing maturation medium, with lowest abundance in globular embryos. Transcripts related toPgGlu-1 became highly abundant again in early cotyledonary embryos but decreased thereafter, whereas transcripts related toPgChi-1 were also highly abundant in late cotyledonary embryos and plantlets in vitro; transcripts were either low (PgChi-1) or were not detectable (PgGlu-1) in needles. Wounding, drying and flooding stresses enhancedPgChi-1-andPgGlu-1-related gene expression. Fungal cell wall suspension enhancedPgGlu-1-related transcript accumulation, but reducedPgChi-1-related transcript abundance within 24 h.PgChi-1 andPgGlu-1 and their homologues may have roles in plant defense, and possibly developmental roles during spruce somatic embryo maturation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Embryo abundant gene ; Gene expression ; Polyethylene glycol ; Picea ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryogenic tissues of white spruce [Picea glauca (Moench) Voss] remain in an early developmental stage while cultured on 2,4-dichlorophenoxyacetic acid and N6-benzyladenine, but develop to cotyledonary embryos when these phytohormones are replaced by abscisic acid. Twenty-eight cDNAs were isolated from cotyledonary embryos by differential screening against immature embryo and non-embryonic tissues. Temporal expression patterns of these cDNAs during ABA-stimulated somatic embryo development were observed. This showed that clones could be allocated to various groups, including embryo-abundant, embryo-maturation-induced, and those whose expression was modulated during embryo development, germination or in non-embryogenic tissues. Expression corresponding to these cDNA clones showed that there were various responses to exogenous ABA or polyethylene glycol during a period of 48 h. Analyses of DNA and predicted amino acid sequence revealed that 12 of 28 cDNA clones had no known homologues, while others were predicted to encode different late-embryogenesis-abundant proteins, early methionine-labelled proteins, storage proteins, heat-shock proteins, glycine-rich cell wall protein, metallothionein-like protein and some other metabolic enzymes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 403-412 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transfer constants to chain-transfer agent (CTA) and to monomer can be obtained by consideration of the complete molecular weight distribution, using the slope of a plot of the natural logarithm of number-molecular weight distribution against molecular weight, in the limit of high molecular weight and low radical flux (P. A. Clay, R. G. Gilbert, Macromolecules 28, 552 (1995)). This method is applied to the bulk polymerisations of methyl methacrylate (MMA) with added triethylamine (TEA) and with added tert-dodecylmercaptan (mixture of 2,4,4,6,6-pentamethylheptane-2-thiol and 2,2,4,6,6-pentamethylheptane-4-thiol, TDM). The transfer rate coefficients are found to be 74 (±20) dm3 · mol- · s-l at 60°C for TEA, and 56 (±13) dm3 · mol-1 · s-1 at 25°C for TDM.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 663-663 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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