Manduca sexta toxicity

Kruger, D. and D. Walters. 1996. Evaluation of the Pollen Expression of CrylA(c) Insecticidal Protein in DEKALB Transformant DBT418 Using Manduca sexta Toxicity Assays Lab Project Number DGC-95-A21. Unpublished study prepared by DEKALB Genetics Corp. and Wildlife Int l. Ltd. 43 p. 

The 29-fluorophytosterols (Fig. 3) all showed significant impairment of growth and development of larval tobacco hornworms when fed at 1 to 100 ppm to Manduca sexta. It is clear that the A22 sterols and were more toxic and caused more severe... 

In addition to the circumstantial iji vivo evidence for fluorocitrate as the ultimate biochemical lesion we desired to demonstrate unambiguously that it was produced as a metabolite of 29-fluorostigmasterol. The toxicity of fluorocitrate and the resulting lethal accumulation of citrate in mouse, fly and cockroach tissues have been shown in early experiments with fluoroacetamide and fluoroacetate(24). However, to our knowledge, complete characterization of (2R,3R)-2-fluorocitrate as the lethal metabolite in vivo has not previously been reported. We thus prepared( ) [29- ]-29-fluorostigmasterol, [29- H]-29-Huorositosterol and [16- H]-16-fluorohexadec-9-enoic acid to enable isolation of [2-3H]-2-fluorocitrate from vivo incubations using Manduca sexta. 

The wild tomato, Lycopersicon hirsutum f, glabratum is covered with trichomes which contain 2-tridecanone. The level of this compound is much lower in the domesticated tomato, U esculentum. This exudate proved to be toxic to Manduca sexta (tobacco hornworm) and to Heliothis zea (121). The density of glandular trichomes, which secrete 2-tridecanone, was influenced... 

A mixture of A -hydroxyacylnornicotines (4), including lV -(3-hydroxy- 12-methyl-tridecanoyl)nomicotine as the major component, was extracted from leaves of Nicotiana repanda, N. stocktonii and N. nesophila [63]. The mixture was toxic to larvae of the tobacco homworm, Manduca sexta [63]. Feeding experiments with [2-14C]-nicotine and [2-l cj-nornicotine suggested that the hydroxyacylnomicotines were biosynthesized in trichomes and then rapidly secreted from the plant [64], The hydroxyacylnomicotines inhibited the growth of wheat coleoptiles and displayed antibiotic activity [65]. 

Lepidopteran larvae exposed to anthranilic diamides exhibit rapid feeding cessation, general lethargy, constrictive muscle paralysis, and regurgitation. One of the earliest symptoms observed was reduction in heart rate. Manduca sexta larvae showed greater than a 50% decrease in heart beat frequency ten minutes following injection with Rynaxypyr (30 ng). Among anthranilic diamides evaluated, similar rank potency was found for this cardio-inhibitory effect and lepidopteran toxicity. 

It was mentioned earlier in this chapter that alkaloids have no selective toxicity to invertebrates. Therefore, for many insects, these compounds are more attractive than toxins (Figure 4.5). The cases of butterfly or beetle behaviors just mentioned are very evident examples of the importance of plants for invertebrates. In both cases, alkaloids are secondary compounds that take part in the attraction for feeding. Moreover, it is also known that Manduca sexta flourish on alkaloid-rich Nicotiana plants and bmchid beetles BrucMdius villosus) on quinolizidine-alkaloid-iich plants.Such examples are a consequence of the herbivore model for choosing a specific plant diet. This model is based on the plant-herbivore interaction. The plant alone can either attract or deter the insect adult or larvae. It is necessary to highlight that alkaloids represent only one group of the secondary compounds through which plants worldwide interact with insects and other animals. 

Lepidopteran larvae exposed to anthranilamides exhibit rapid feeding cessation, general lethargy, and partial paralysis. Further, dorsal vessel (heart) studies with DP-012, revealed a rapid cardio-inhibitoiy effect in Manduca sexta larvae. Contraction frequency was attenuated in a dose-dependent manor with injection of 3 ng/g (body weight) attenuating the contraction by 27%. As shown in Table II, the rank potency for anthranilamides is comparable to its lepidopteran toxicity with DP-012 > DP-010 > DP-002. 

Nicotine (43) inhibits radicle growth in Lepidium and is toxic to Lemna (Wink, 1993). It is a useful insecticide and probably serves as a defensive compound in the plant (Wink, 1993). Some coadapted insects, such as the tobacco horn-worm, Manduca sexta, are highly resistant to the effects of... 

Jenkins, J.L., M.K. Lee, S. Sangadala, M.J. Adang, and D.H. Dean. 1999. Binding of Bacillus thuringiensis Cryl Ac toxin to Manduca sexta aminopeptidase-N receptor is not directly related to toxicity. FEBS Lett. 462 373-376. 

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