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  • 1
    ISSN: 1573-5028
    Keywords: Arabidopsis ; transgenic plants ; auxin ; hypocotyl elongation ; photomorphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transgenic Arabidopsis thaliana plants constitutively expressing Agrobacterium tumefaciens tryptophan monooxygenase (iaaM) were obtained and characterized. Arabidopsis plants expressing iaaM have up to 4-fold higher levels of free indole-3-acetic acid (IAA) and display increased hypocotyl elongation in the light. This result clearly demonstrates that excess endogenous auxin can promote cell elongation in a whole plant. Interactions of the auxin-overproducing transgenic plants with the phytochrome-deficient hy6-1 and auxin-resistant axrl-3 mutations were also studied. The effects of auxin overproduction on hypocotyl elongation were not additive to the effects of phytochrome deficiency in the hy6-1 mutant, indicating that excess auxin does not counteract factors that limit hypocotyl elongation in hy6-1 seedlings. Auxin-overproducing seedlings are also qualitatively indistinguishable from wild-type controls in their response to red, far-red, and blue light treatments, demonstrating that the effect of excess auxin on hypocotyl elongation is independent of red and blue light-mediated effects. All phenotypic effects of iaaM-mediated auxin overproduction (i.e. increased hypocotyl elongation in the light, severe rosette leaf epinasty, and increased apical dominance) are suppressed by the auxin-resistant axr1-3 mutation. The axr1-3 mutation apparently blocks auxin signal transduction since it does not reduce auxin levels when combined with the auxin-overproducing transgene.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0192-253X
    Keywords: Run-on transcription ; developmentally regulated gene expression ; follicle cell nuclei ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: To determine the relative roles of transcriptional and post-transcriptional events in establishing the temporal pattern of chorion gene expression in Drosophila, we have examined chorion gene transcription, RNA accumulation, and protein synthesis in follicles of selected pre-early- and late-choriogenic stages. Chorion gene transcription was assayed in follicle cell nuclei by nuclear run-on reactions. For the s 15, s 16, s 18, s36, and s38 chorion genes, the periods of intense transcription are as predicted from the dynamics of RNA accumulation and protein synthesis, indicating that these genes are primarily regulated at the transcriptional level. In contrast, gene s19 appears subject to post-transcriptional control at stage 14, when transcription rates are substantially higher than predicted from the observed RNA levels.Transcription of regions between the clustered and tandemly oriented chorion genes was also examined. In contrast to many RNA polymerase II transcribed genes, for the s18 and s36 chorion genes run-on transcription appears to terminate within about 100 base pairs downstream of the polyadenylation sites, corroborating previous reports based on electron microscopy of s36 [Osheim et al., EMBO J 5:3591-3596, 1986].
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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