Development of broad-spectrum insect-resistant tobacco by expression of synthetic cry1Ac and cry2Ab genes

Abstract

Efficacy of two newly synthesized cry1Ac and cry2Ab genes was checked in tobacco before their expression in cotton. Both genes were artificially synthesized and codon optimized with respect to cotton-preferred codon usage. These genes were cloned in a plant expression vector and then transformed into tobacco. Fifty-eight putative transgenic plants were recovered from the selected explants. Successful integration of both genes in plant genome was confirmed by PCR amplification. Expression of transgenes was confirmed by PCR amplification from total plant RNA. Detached leaf insect bioassays were conducted with Helicoverpa armigera and Spodoptera exigua larvae. About 12 % of the transgenic plants showed significantly high resistance to S. exigua. Significant mortality (62 %) of H. armigera was recorded within 24 h of bioassays. Both toxins showed synergistic effect in tobacco and broadened the spectrum of plant activity against insects.

Mendelian segregation pattern and expression studies of insecticidal gene (cry1Ac) in insect resistant cotton progeny

“…The advent of genetic engineering technologies has helped plant reseachers to transfer genes from irrelevant origin into significantly important crop plants to induce insect resistance (Dhaliwal et al, 1998). Insect resistant Bt plants have emerged as potential alternative to the synthetic insecticides (Khan et al, 2011;Sohail et al, 2012).…”

Current trends in genetic manipulations to enhance abiotic and biotic stresses in tobacco

“…Resistance to Spodoptera exigua and Helicoverpa armigera larvae Sohail et al (2012) Cadherin gene silencing…”

“…Insect resistant transgenic plants have emerged as potential alternatives to the synthetic insecticides. Genes encoding the insecticidal crystal protein were isolated from Bacillus thuringiensis (Bt) and successfully transformed into plants to produce insectresistant plants (Porta et al, 2011;Sohail et al, 2012). Bt toxins are safe to non-target insects due to their specific activity towards target insects.…”

“…This problem was overcome by expressing more than one toxin simultaneously. Sohail et al (2012) investigated a combination of toxins such as cry1Ac and cry1Ab, artificially constructed genes, to broaden the action spectrum in tobacco. They found 12% and 62% resistance to Spodoptera exigua and Helicoverpa armigera larvae.…”

“…Resistance to Cry toxins, produced by B. thuringiensis, has been linked with mutations in the cadherin gene (Porta et al, 2011;Sohail et al, 2012). One strategy effective to overcome larval resistance to Cry1A toxins is the production of Cry1AMod toxins that lack helix α-1since helix α-1is responsible for resistance (Porta et al, 2011).…”