Abstract
Study and research of Bt (Bacillus thuringiensis) transgenic plants have opened new ways to combat insect pests. Over the decades, however, insect pests, especially the Lepidopteran, have developed tolerance against Bt delta-endotoxins. Such issues can be addressed through the development of novel toxins with greater toxicity and affinity against a broad range of insect receptors. In this computational study, functional domains of Bacillus thuringiensis crystal delta-endotoxin (Cry1Ac) insecticidal protein and vegetative insecticidal protein (Vip3Aa) have been fused to develop a broad-range Vip3Aa-Cry1Ac fusion protein. Cry1Ac and Vip3Aa are non-homologous insecticidal proteins possessing receptors against different targets within the midgut of insects. The insecticidal proteins were fused to broaden the insecticidal activity. Molecular docking analysis of the fusion protein against aminopeptidase-N (APN) and cadherin receptors of five Lepidopteran insects (Agrotis ipsilon, Helicoverpa armigera, Pectinophora gossypiella, Spodoptera exigua, and Spodoptera litura) revealed that the Ser290, Ser293, Leu337, Thr340, and Arg437 residues of the fusion protein are involved in the interaction with insect receptors. The Helicoverpa armigera cadherin receptor, however, showed no interaction, which might be due to either loss or burial of interactive residues inside the fusion protein. These findings revealed that the Vip3Aa-Cry1Ac fusion protein has a strong affinity against Lepidopteran insect receptors and hence has a potential to be an efficient broad-range insecticidal protein.
Highlights
Cotton (Gossypium hirsutum) is among the most important crops worldwide, cultivated in more than 80 countries
The functional domains of Cry1Ac-Vip3Aa fusion protein sequence were defined using the InterPro tool (Figure 1), which was further subjected to modeling
The resulted Cry1Ac-Vip3Aa fusion protein model consisted of 892 residues (Cry1Ac; 1-616 residues and Vip3Aa; 617-892 residues)
Summary
Cotton (Gossypium hirsutum) is among the most important crops worldwide, cultivated in more than 80 countries. There are many threats to cotton production, including weeds, insect pests, drought and cotton leaf curl virus (CLCuV). Fusion Protein Against Lepidopteran Insects of the total global cotton crop (http://www.statista.com/study/ 15461/cotton-statista-dossier/). China is the leading importer, with a global share of 20%. The US is the leading exporter of cotton, with a global share of 42% (Sabir et al, 2011). The use of genetically modified plants, especially Bt (Bacillus thuringiensis) transgenic plants, has opened new channels to control such control problems that arise from insect-pests (Schnepf et al, 1998). The first transgenic cotton with crystal delta-endotoxin insecticidal protein from the gram-positive bacterium Bacillus thuringiensis (Cry1Ac) was commercially available in 1995 (Ellsworth et al, 2000), and since many new advances have been achieved
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