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The aim of the present study was to explore the usability of Arabidopsis cruciferin C (CRUC) promoter in the Cre/loxP self-excision strategy with the minimal rate of an ectopic expression of the cre recombinase. For this, a plant transformation vector containing the gus reporter gene driven by the light-sensitive Lhca3.St1 instead of double dCaMV 35S promoter and one pair loxP sites flanking the cre and the nptII genes was prepared. Agrobacterium-mediated transformations of three economically important oilseed rape (Brassica napus L.) cultivars Campino, Hunter and Topas as well as tobacco (Nicotiana tabacum L.) as a reference system were performed. The integration of the T-DNA into genome of all Brassica cultivars was accompanied by DNA deletions/rearrangements on the both T-DNA ends. The disruption of the Cre/ loxP recombination system in oilseed rape was observed. On the contrary, no such events were detected in tobacco. The applied strategy did restrict an ectopic CRUC activity to some extent and a set of transgenic tobacco T₀ plants without premature excision event was obtained. Our data showed that a choice of the promoter can limit undesired activation of the Cre/loxP cassette.
Flax suspension cultures have been established from the callus induced from the cotyledons, hypocotyls, and immature zygotic embryos (iZE). The growth of flax suspension culture (expressed as a sedimented cell volume) was compared in both conditioned (by liquid from embryogenic Pinus nigra suspension culture) and nonconditioned media. Conditioning of media significantly increased the growth of the cell lines of hypocotyl and iZE origin; however, it had no promotive effect on embryogenic response of these flax liquid cultures. Formation of embryo-like structures (ELS), confirmed also histologically, has only been found in the cell line derived from iZE and cultivated in non-conditioned MS medium supplemented with 1 mg l⁻¹ 2,4-D. The process of ELS formation in this cell line was accompanied by the expression of the protein(s) with chitinolytic activity and molecular weight approximately of 25 kDa. The relationship between the formation of ELS and secretion of chitinase(s) is discussed.
The Cre/loxP-based self-excision represents a promising strategy for removal of hazardous transgene(s) from genomes of targeted crops prior to their introduction into environment. Here, we applied the Cre/loxP self-excision strategy in which the cre recombinase gene is driven by the embryo-specific CRUC promoter from Arabidopsis thaliana. Besides, the Cre/loxP cassette, the T-DNA also consisted of the β-glucuronidase gene, controlled by the double dCaMV 35S promoter and the selectable neomycin phosphotransferase gene; the latter was aimed to be removed from the transgenic genome. The Cre/loxP self-excision cassette was introduced into genomes of four commercial oilseed rape cultivars Haydn, Heros, Hunter and Topas (Brassica napus L.) via Agrobacterium tumefaciens. Transgenic T₀ plants were regenerated from all cultivars. Their detailed molecular analyses revealed premature activation of the CRUC promoter that resulted in partial excision of the nptII gene. Progenies of four self-pollinated T₀ lines were further analysed, and the data confirmed complete excision event in 5 out of 105 (4.8%) of T₁ transgenic oilseed rape plants. The excision efficiency does not seem to depend on the target cultivar. However, the poor transformation efficiency of rapeseed and the limited specificity of the CRUC promoter are clearly the bottleneck of this approach, and the feasibility of (tissue-specific) self-excision of selectable marker gene from genomes of each commercial rapeseed variety adds to their perspective to cope the increasing negative impacts of climate changes.
The genes encoding for a cucumber class III chitinase and Nicotiana plumbaginifolia class I glucanase were co-introduced into Slovak potato (Solanum tuberosum L.) cultivar ETA using Agrobacterium tumefaciens. Expression of both genes was driven by wound-inducible polyubiquitin promoter isolated from Slovak potato breeding line 116/86. Analyses showed inducible, peel-specific expression of both transgenes under stress conditions. The effect of transgene expression on fungal susceptibility of transformants was evaluated in vitro and in vivo. Experiments with crude protein extracts isolated from transgenic microtubers showed growth inhibition of Rhizoctonia solani hyphae in the range from 7.3 to 14.2%. In contrast, experiments performed in growth chamber conditions revealed that the polyubiquitin promoter driven transgene expression did not ensure any obvious increase of transgenic potato resistance against Rhizoctonia solani.
Arsenic is a serious soil pollutant with toxic effects on biological systems. Elevated soil concentrations may negatively affect crop production and food safety. The impact of arsenic on plants depends on many factors, including nitrogen availability. Nitrogen (N) as an essential mineral affects overall energetics of plants, while its non-optimal doses have been shown to also impact plant performance and yield, as well as tolerance to environmental constraints. The combined effects of these two factors, however, have been rarely studied. Here we investigated the impact of sublethal doses of As³⁺ (5 mM) on wheat plants grown in hydropony, applying a set of 8 different N concentrations spanning from starvation (0 mM N in the media) through optimum (7.5 mM N) to excessive amounts (up to 35 mM N). The results showed that the content of photosynthetic pigments varies depending on N concentration and As³⁺ presence. The different energetic status of plants also affected the final As uptake. Establishing nutrition conditions might be important for limiting metal(loid) uptake from soil in contaminated areas.
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