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  • 1
    Electronic Resource
    Electronic Resource
    Factors influencing Agrobacterium-mediated transient expression of gusA in rice (1992)
    Springer
    Plant molecular biology 20 (1992), S. 1037-1048 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium ; rice ; transformation ; Ti plasmid ; GUS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transient expression of GUS in rice (Oryza sativa L.) mediated by Agrobacterium tumefaciens was characterized using binary vectors containing gusA genes that express minimal (pKIWI105 and pCNL1) or no (p35S-GUS-INT and pCNL56) GUS activity in bacteria. Four-day old seedlings obtained from seeds or immature embryos of rice were cut into shoot, root, and seed remnants and inoculated with various strains of A. tumefaciens. Transient GUS expression events were quantitated histochemically by determining the frequency of explants exhibiting blue spots indicative of GUS at four to six days after cocultivation with A. tumefaciens. A. tumefaciens strains that did not contain the gusA gene (At643) or a Ti-plasmid (At563 and At657) did not elicit any blue staining characteristic of GUS activity. Several parameters were important in obtaining efficient transient expression of GUS in rice mediated by A. tumefaciens. The growth regulator 2,4-D inhibited GUS expression if present during the seed germination period, but the presence of 6 mg/1 2,4-D during cocultivation of the explants with A. tumefaciens slightly enhanced GUS expression efficiency. All 21 rice cultivars tested expressed GUS after co-cultivation with A. tumefaciens. The GUS expression frequency was highest amongst the indica cultivars. The frequencies of GUS expression in japonica cultivars and in Oryza glaberrima cultivars (grown primarily in Africa) were generally one-half to one-third the level found for indica varieties. Leaf explants were more susceptible to A. tumefaciens-facilitated GUS expression than were roots or seed remnants. The vir genes of an agropine-type Ti-plasmid of A. tumefaciens were most effective in directing transient GUS expression in rice, whereas those of a nopaline-type and an octopine-type plasmid were less effective. We have also found that the frequency of transient expression of GUS was higher with pBIN19 as the precursor cloning vector than with pEND4K as the precursor cloning vector. Reasons for differences in effectiveness of these binary vectors are discussed. Using the conditions described here, A. tumefaciens-mediated frequencies of transient GUS expression in four-day old shoots of several rice cultivars were routinely in excess of 50%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028891
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  • 2
    Electronic Resource
    Electronic Resource
    Use of parameter estimation in determining soil hydraulic properties from unsaturated transient flow (1990)
    Springer
    Water resources management 4 (1990), S. 1-19 
    Details
    ISSN: 1573-1650
    Keywords: Soil hydraulic properties ; unsaturation ; parameter estimation ; cumulative drainages ; head profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract This paper proposes a model for determining the parameters given by the closed-form equations of van Genuchten. An objective function is made by the observed data from vertical drainage, and the solutions of optimization show that less computation and more accurate estimates are made as head profiles are taken into account rather than cumulative drainage. Sensitivity analysis of the error vector to parameters interprets this reason. The convergence and stability of solutions are evaluated with different magnitudes of measured errors in the head, and the results show good estimates will be obtained if a sufficient pressure head at the soil bottom is applied. A variable θ k is introduced to avoid the estimations of α and n being affected by the uncertainties of Ks and θ s .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429922
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  • 3
    Electronic Resource
    Electronic Resource
    Genomic organization of an α-zein gene cluster in maize (1992)
    Springer
    Molecular genetics and genomics 231 (1992), S. 304-312 
    Details
    ISSN: 1617-4623
    Keywords: Maize ; Zein ; Gene cluster ; Repetitive sequence ; Cos mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genes encoding the α-zein proteins of maize constitute a large multigene family of some 75 genes. This multigene family can be divided into four subfamilies based on the nucleotide sequences of their genes and the deduced amino acid sequences of their proteins. We describe for the first time evidence of a clustering of five α-zein subfamily 4 (SF4) genes that are members of one of the major α-zein subfamilies in a 56 kb region of the genome of the maize inbred line W22. None of the other three known α-zein gene subfamilies (SF1, SF2, or SF3) are present in this cluster. The genomic region was reconstructed using restriction endonuclease maps to identify and align three overlapping cosmid clones isolated from a genomic library. The α-zein genes are not evenly spaced; the minimum distance between genes is 3.5 kb; the maximum is 13 kb. All the α-zein genes in the cluster have the same transcriptional orientation. The location and sequences of some of the repetitive DNA elements in this gene cluster were determined. We estimate that there are a minimum of eight repetitive DNA elements in this region. The sequences of the repetitive elements (not functionally defined) are located between or among the α-zein genes. The regions containing two of these repetitive elements (Rep1 and Rep4) have been sequenced; they are about 15 kb apart in the genome. These repetitive elements have similar sequences for about 300 by out of the 400 by compared. The regions of sequence similarity, however, are in reverse orientation to one another. Both repetitive elements contain replication origin-like sequences. In addition, Rep4 contains two repeats of a five-base sequence that appear to define its presumptive ends. The presence of the short direct repeats flanking the Rep4 element suggests that the Rep4 element might have originated from a transposition event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279804
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    Paper (German National Licenses)
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