Activity of wild-type and hybrid Bacillus thuringiensis δ-endotoxins against Agrotis ipsilon
ABSTRACT Twelve Cry1 and two Cry9 delta-endotoxins from Bacillus thuringiensis were tested for their activity against black cutworm ( Agrotis ipsilon). A. ipsilon was not susceptible to many toxins, but three toxins had significant activity. Cry9Ca was the most toxic, followed by Cry1Aa and Cry1Fb. Hybrids between these three active proteins were made by in vivo recombination and analyzed for activity against A. ipsilon. Analysis of hybrids between Cry1Aa and Cry1Fb indicated that domain I of Cry1Aa protein was involved in its higher activity.
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- "Domain II, the middle domain, is a b-prism that is implicated in receptor interactions and insect specificity (Rajamohan et al. 1996; Wu and Dean 1996; G omez et al. 2003; Fernández et al. 2008). Domain III, the C-terminus domain, is a b-sandwich that affects receptor interactions, insect specificity (Schnepf et al. 1998; de Maagd et al. 2003), and stabilization of molecular structure (Grochulski et al. 1995). Cry toxins are thought to bind cadherin-like receptors via loop a8 (Gó mez et al. 2003), loop 1 (Wu and Dean 1996), loop 2 (Gó mez et al. 2001), and loop 3 (Xie et al. 2005) of domain II. "
ABSTRACT: Directed evolution of a Cry1Aa toxin using phage display and biopanning was performed to generate an increased binding affinity to the Bombyx mori cadherin-like receptor (BtR175). Three mutant toxins (371WGLA374, 371WPHH374, 371WRPQ37425) with 16-, 16-, and 50-fold higher binding affinities, respectively, for BtR175 were selected from a phage library containing toxins with mutations in domain II loop 2. However, the observed toxicities of the three mutants against B. mori larvae and cultured cells expressing the BtR175 toxin-binding region did not increase, suggesting that increased binding affinity to cadherins does not contribute to the insecticidal activity. Affinity maturation of a Cry toxin to a receptor via directed evolution was relatively simple to achieve, and seems to have potential for generating a toxin with increased insecticidal activity.MicrobiologyOpen 08/2014; 3(4). DOI:10.1002/mbo3.188 · 2.21 Impact Factor
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- "Oliver et al. 2003, 2005, 2008, 2010; Scarborough et al. 2005; Douglas 2006; Nakabachi et al. 2006; Thao and Baumann 2004; Baumann et al. 2002; Kaltenpoth 2009; Schoenian et al. 2011; Oh et al. 2009a, b, 2011; Brachmann et al. 2006; Piel et al. 2004; Barke et al. 2010; Haeder et al. 2009; Scott et al. 2008; Leroy et al. 2011; Sabri et al. 2010) and several examples illustrate pathogenic interactions (e.g. Grenier et al. 2006; Harada and Ishikawa 1997; Ffrench-Constant et al. 2007; Herbert and Goodrich-Blair 2007; Harada et al. 1997; Lecadet et al. 1999; Schnepf et al. 1998; de Maagd et al. 2003) while the semiochemically mediated interactions are more rarely described. However, plenty of bacteria have been "
ABSTRACT: In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests. KeywordsSemiochemically mediated interactions–Bacterial volatiles–Semiochemicals–Behaviours–Insects–Pests–Biological controlChemoecology 09/2011; 21(3):113-122. DOI:10.1007/s00049-011-0074-6 · 1.92 Impact Factor
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ABSTRACT: PurposeThe prevailing controversies on the potential environmental risks of genetically modified organisms [GMOs] still fuel ongoing discussions among European Union [EU] member states, risk assessors, applicants and scientists, even several years after the commercial introduction of GMOs. The disagreements mainly derive from the current risk assessment practice of GMOs and differences in the perceived environmental risks. Against this background, the aim of this study was to scrutinize the current practice of environmental risk assessment [ERA] of several GMO applications currently pending for authorisation in the EU. MethodsWe analysed the data presented for three assessment categories of the ERA of genetically modified [GM] maize applications for cultivation in the European Union: the agronomic evaluations and the assessments of the effects of GM maize on target organisms and of its potential adverse effects on non-target organisms. ResultsMajor shortcomings causing considerable uncertainties related to the risk assessment were identified in all three categories. In addition, two principles of Directive 2001/18/EC are largely not fulfilled - the consideration of the receiving environment and the indirect effects, as mediated, e.g. by the application of the complementary herbicide in the case of herbicide-tolerant GM maize. ConclusionsWe conclude that the current practice of ERA does not comprehensively fulfil the scientific and legal requirements of Directive 2001/18/EC, and we propose improvements and needs for further guidance and development of standards. The recommendations address likewise applicants, risk assessors as well as decision makers.01/2011; 23(1):1-15. DOI:10.1186/2190-4715-23-33