Target and non‐target effects of a spider venom toxin produced in transgenic cotton and tobacco plants

Abstract

The peptide ω‐Hexatoxin‐Hv1a (Hvt) is one of the most studied spider toxins. Its insecticidal potential has been reported against species belonging to the arthropod orders Lepidoptera, Diptera and Orthoptera. The gene encoding Hvt has been transformed into cotton and tobacco to protect the plants from damage by lepidopteran pests. This study evaluated the expression of the ω‐HXTX‐Hv1a gene in transgenic plants, and the toxicity of plant‐expressed and purified Hvt on target lepidopteran insects and on several non‐target species. Transgenic Bollgard II cotton plants, which produce Cry1Ac and Cry2Ab2 and purified Cry2Ab2 protein were included in the study as comparators. LC95 values of purified Hvt against Spodoptera littoralis and Heliothis virescens were 28.31 and 27.57 μg/ml of artificial diet, respectively. Larval mortality was 100% on Hvt‐transgenic tobacco plants but not on Hvt‐transgenic cotton, probably because of the significantly lower toxin expression level in the transgenic cotton line. Non‐target studies were conducted with larvae of the predators Chrysoperla carnea and Coccinella septempunctata, adults of the aphid parasitoid Aphidius colemani, and adult workers of the honey bee, Apis mellifera. Even at 40 μg/ml, Hvt did not adversely affect the four non‐target species. Purified Cry2Ab2 at 10 μg/ml also did not adversely affect any of the non‐target species. Our results show that Hvt might be useful for developing insecticidal plant varieties to control pest Lepidoptera.

A sugarcane mosaic virus vector for rapid in planta screening of proteins that inhibit the growth of insect herbivores

“…Although expression of Hvt , ACA and GNA increased resistance in other plant‐insect interaction studies (Ullah et al ., 2015 ; Liu et al ., 2016 ; Vandenborre et al ., 2011 ), expression of these single‐gene SCMV constructs in maize did not significantly reduce S. frugiperda weight gain. Nevertheless, expression of gene fusions, Hvt‐ACA and Hvt‐GNA , reduced S. frugiperda weight gain, indicating that there are additive effects of the spider venom and the lectin (Figure 5c,i ).…”

“…UyCT3 and UyCT5, two antimicrobial peptides that are produced in the venom glands of Urodacus yaschenkoi (inland robust scorpion) decrease the fitness of Acyrthosiphon pisum (pea aphid) and the density of the primary symbiont, Buchnera aphidicola , suggesting that those are promising candidates for the production of insect‐resistant transgenic plants (Luna‐Ramirez et al ., 2017 ). Similarly, Hvt from H. versuta is broadly effective against both lepidopteran and hemipteran pests when expressed in transgenic plants (Ullah et al ., 2015 ; Javaid et al ., 2016 ; Rauf et al ., 2019 ). Given the broad insecticidal activity of these spider and scorpion venom proteins, we hypothesized that they would also be effective in reducing S. frugiperda growth.…”

A transgenic approach to control hemipteran insects by expressing insecticidal genes under phloem-specific promoters

“…Hvt, when expressed from a bacterial expression system, was topically toxic to insects. In feeding experiments with the chewing herbivores H. armigera and Spodoptera littoralis (Egyptian cotton leafworm), insects on transgenic plants expressing Hvt from the 35S promoter were dead within 24 h 53 54 55 56 .…”

Rapid screening of pest resistance genes in maize using a sugarcane mosaic virus vector

“…Although these genes increased resistance in other plant-insect studies (Liu et al, 2016;Ullah et al, 2015;Vandenborre et al, 2011), overexpression of Hvt, ACA, and GNA as singlegene SCMV constructs in maize did not significantly reduce S. frugiperda weight gain. Nevertheless, expression of gene fusions, Hvt-ACA and Hvt-GNA, reduced S. frugiperda weight gain, indicating that there are additive effects of the spider venom and the lectin (Figure 5c,i).…”

“…UyCT3 and UyCT5, two antimicrobial peptides that are produced in the venom glands of Urodacus yaschenkoi (inland robust scorpion) decrease the fitness of Acyrthosiphon pisum (pea aphid) and the density of the primary symbiont, Buchnera aphidicola, suggesting that those are promising candidates for the production of insect-resistant transgenic plants (Luna-Ramirez et al, 2017). Similarly, ω-hexatoxin Hv1a (Hvt, also called ω-ACTX Hv1a) from Hadronyche versuta (Blue Mountains funnel web spider) is broadly effective against both lepidopteran and hemipteran pests when expressed in transgenic plants (Javaid et al, 2016;Ullah et al, 2015;Rauf et al, 2019). Given the broad insecticidal activity of these spider and scorpion venom proteins, we hypothesized that they would also be effective in reducing S. frugiperda growth.…”