Insect resistance of transgenic tobacco plants expressing delta-endotoxin gene of Bacillus thuringiensis.
The initiative B.thuringiensis delta-endotoxin (Bt toxin) gene clones TH12 and TH48 contain two different classes of homologous genes, the 5.3 kb class and 6.6 kb class, respectively. Bt toxin genes of both classes, modified at the 5'-end and truncated at the 3'-end, can still be expressed to produce the insecticidal, truncated toxin proteins in E. coli. The modified Bt toxin genes were inserted into the plant binary expression vector pBin 437 (a derivative plasmid of pBin 19) and were transferred into tobacco by Ti plasmid-mediated gene transfer system. Southern blot and DNA slot blot analysis indicate that the Bt toxin genes have been integrated into tobacco genome at a copy number of 1 to 5. Northern blot analysis of polyA+ RNAs from progeny of the transgenic plants revealed that Bt toxin genes of both 5.3 kb and 6.6 kb classes were expressed in transgenic plants, though the transcripts were degraded to RNAs of lower molecular weights. In insecticidal test, 5 plants from the progeny of 5.3 kb class gene-transformed SR1 tobacco plants and 3 plants from those of 6.6 kb class gene-transformed plants were found to be toxic to the testing larvea of H.assulta. In comparison with the control, mortality of the insects fed on transgenic plants reached 40-50% and the growth of the survived insects was remarkably inhibited. These results indicate that the modified Bt genes of the 5.3 kb and 6.6 kb classes were expressed in transgenic plants and could confer on the transgenic plants a new character of insect resistance.
Available from: Luc Belzunces
- "During the past decade, the impacts of new insecticide families and biotechnological processes on cognitive functions have received special attention. Researches were conducted on the insecticide families, neonicotinoids and phenyl pyrazoles, developed in the mid-1990s (Schroeder and Flattum 1984; Johnston et al. 1986; Elbert et al. 1990; Klis et al. 1991a, b; Colliot et al. 1992; Sadler and Nieh 2011), and on the Bacillus thuringiensis toxins used in the development of genetically modified plants (GMP; Barton et al. 1987; Vaeck et al. 1987; Hofte and Whiteley 1989; Leemans et al. 1990; Tian et al. 1991; Jansens et al. 1992). The neonicotinoid family was first investigated in studies on its leading representative, imidacloprid , using various protocols based on olfactive conditioning. "
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ABSTRACT: During their foraging activity, honey bees are often exposed to direct and residual contacts with pesticides, especially insecticides, all substances specifically designed to kill, repel, attract or perturb the vital functions of insects. Insecticides may elicit lethal and sublethal effects of different natures that may affect various biological systems of the honey bee. The first step in the induction of toxicity by a chemical is the interaction between the toxic compound and its molecular target. The action on the molecular target can lead to the induction of observable or non-visible effects. The toxic substance may impair important processes involved in cognitive functions, behaviour or integrity of physiological functions. This review is focused on the neural effects of insecticides that have repercussions on (a) cognitive functions, including learning and memory, habituation, olfaction and gustation, navigation and orientation; (b) behaviour, including foraging and (c) physiological functions, including thermoregulation and muscle activity.
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ABSTRACT: Glycinebetaine is an important quaternary ammonium compound generated in response to salt and other osmotic stresses in many organisms. Its synthesis requires the catalysis of betaine aldehyde dehydrogenase encoded by a Betaine Aldehyde Dehydrogenase (BADH) gene that converts betaine aldehyde into glycinebetaine in some halotolerant plants. In this study, a BADH gene was over expressed in transgenic alfalfa (Medicago sativa L) plants using Agrobacterium-mediated transformation. Transgenic alfalfa plants grown under 9‰ NaCl grew well; while non-transgenic control plants turned yellowish in color, wilted, and eventually died. Polymerase chain reaction (PCR) and Northern blot hybridization analyses demonstrated that the BADH gene was transferred into the T2 generation and segregated in a Mendelian fashion. Transgenic alfalfa plants expressing BADH showed significantly higher BADH enzyme activity and betaine contents when grown under 6‰ NaCl. Moreover, proline content in T2 lines were higher while electrolyte leakage and malonaldehyde content were lower in T2 lines compared with non-transgenic plants. These findings indicated that transgenic plants expressing BADH transgene exhibited higher salt tolerance than non-transgenic plants.
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ABSTRACT: Insect-resistant poplar (Populus nigra L.) plants have been produced by infecting leaves withAgrobacterium tumefaciens strains carrying a binary vector containing different truncated forms of aBacillus thuringiensis (B.t.) toxin gene under a duplicated CaMV 35S promoter. Putative transgenic plants were propagated by cuttings at two experimental farms (in Beijing and Xinjiang, China). At 2–3 years after transformation, 17 of them were selected on the bases of insect-tolerance and good silvicultural traits, and evaluated for insect resistance, for the presence of theB.t. toxin DNA fragment (Southern blots and PCR) and for the expression of the transgene (western and northern blots). Somaclonal variation, as suggested by the appearance of permanent changes in the shape of the leaves, was also investigated with molecular tools (RFLP (restriction fragment length polymorphism), RAPD (random amplified polymorphic DNA) and microsatellite DNA).
Bioassays withApochemia cineraius andLymantria dispar on the leaves of the selected clones showed different and, in some cases, high levels of insecticidal activity. The molecular analysis demonstrated integration and expression of the foreign gene. Somatic changes were correlated to extensive genomic changes and were quantified in dendrograms, in terms of genomic similarity. The analysis of control plants suggested that genomic changes were correlated to thein vitro culture step necessary forA. tumefaciens-mediated gene transfer, rather than to the integration of the foreign genes.
Three transgenic clones (12, 153 and 192), selected for insect resistance, reduced morphological changes and promising silvicultural traits, are now under large-scale field evaluation in six different provinces in China.
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