Isolation of an orally active insecticidal toxin from the venom of an Australian tarantula

Hardy, Margaret C., Daly, Norelle L., Mobli, Mehdi, Morales, Rodrigo A.V., and King, Glenn F. (2013) Isolation of an orally active insecticidal toxin from the venom of an Australian tarantula. PLoS ONE, 8 (9). e73136. pp. 1-12.

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Abstract

Many insect pests have developed resistance to existing chemical insecticides and consequently there is much interest in the development of new insecticidal compounds with novel modes of action. Although spiders have deployed insecticidal toxins in their venoms for over 250 million years, there is no evolutionary selection pressure on these toxins to possess oral activity since they are injected into prey and predators via a hypodermic needle-like fang. Thus, it has been assumed that spider-venom peptides are not orally active and are therefore unlikely to be useful insecticides. Contrary to this dogma, we show that it is possible to isolate spider-venom peptides with high levels of oral insecticidal activity by directly screening for per os toxicity. Using this approach, we isolated a 34-residue orally active insecticidal peptide (OAIP-1) from venom of the Australian tarantula Selenotypus plumipes. The oral LD50 for OAIP-1 in the agronomically important cotton bollworm Helicoverpa armigera was 104.2±0.6 pmol/g, which is the highest per os activity reported to date for an insecticidal venom peptide. OAIP-1 is equipotent with synthetic pyrethroids and it acts synergistically with neonicotinoid insecticides. The three-dimensional structure of OAIP-1 determined using NMR spectroscopy revealed that the three disulfide bonds form an inhibitor cystine knot motif; this structural motif provides the peptide with a high level of biological stability that probably contributes to its oral activity. OAIP-1 is likely to be synergized by the gut-lytic activity of the Bacillus thuringiensis Cry toxin (Bt) expressed in insect-resistant transgenic crops, and consequently it might be a good candidate for trait stacking with Bt.

Item ID: 32118
Item Type: Article (Research - C1)
ISSN: 1932-6203
Additional Information:

Copyright: © 2013 Hardy et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funders: Australian Research Council (ARC), University of Queensland Research Scholarship, Australian Government International Postgraduate Research Scholarship
Projects and Grants: Australian Research Council (Discovery Grant DP0774245)
Date Deposited: 30 Apr 2014 01:16
FoR Codes: 03 CHEMICAL SCIENCES > 0304 Medicinal and Biomolecular Chemistry > 030401 Biologically Active Molecules @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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