Development and Evaluation of Synthetic vip3A Gene in Transgenic Cotton for Protection against Chewing Insect Pests

Abstract

Insect pests are among the main factors limiting crop productivity worldwide, amongst which lepidopteran pests contribute a significant amount of damage. Genetically modified crops provide useful germplasm for the protection of various commercial agricultural commodities against insect pest infestation. The codon-optimized synthetic vip3A gene was designed, synthesized and cloned in a plant expression vector under CaMV 2X 35S promoter and CaMV terminator that subsequently transformed in Gossypium hirsutum cv. Coker-312 to estimate its efficacy against two lepidopteran insects, i.e., Helicoverpa armigera and Spodoptera litura. Twenty-eight putative T0 transgenic plants were recovered from the agro-inoculated hypocotyls following callus formation, selection and embryogenesis. PCR amplification and Southern hybridization revealed the successful vip3A transgene integration into plant nuclear genome. Transgenic lines of various transformed events were subjected to detached leaf insect bioassays using first-instar larvae of H. armigera and S. litura. A complete insect mortality of H. armigera and S. litura was observed in 96 h after the release of caterpillars under laboratory conditions. Moreover, the observed LT50 for H. armigera (1.01 days) and S. litura (1.26 days) suggests the high expression of self-designed codon-optimized synthetic vip3A toxin in these cotton lines. The enhanced insecticidal expression of synthetic vip3A gene has shown great potential for its inclusion in the list of promising genes that can be used to develop insect resistant transgenic plants. © 2021 Friends Science Publishers