Expression of modified snowdrop lectin (Galanthus nivalis agglutinin) protein confers insect resistance in Arabidopsis and cotton

Abstract Background: Cotton is a major fiber crop in the world that can be severely infested by pests in agricultural fields. Identifying new insect-resistance genes and increasing expression of known insect-resistance genes are imperative in cultivated cotton. Galanthus nivalis agglutinin, a type of plant lectin that is reportedly toxic towards Homoptera sap-sucking pests when administered in their artificial diet or when fed transgenic plant material expressing the gene. The natural GNA gene is mainly expressed in monocotyledons instead of in dicotyledons, thus modification of the gene is necessary to effectively express the GNA gene in transgenic cotton. Results: We report the artificial synthesis of a modified GNA gene (ASGNA), via codon augmentation, and its insertion into Arabidopsis thaliana and cotton to test its efficacy as an insect-resistance gene against cotton aphids and Plutella xylostella. The level of ASGNA expression in transgenic plants was determined by the enzyme-linked immunosorbent assay (ELISA), and the amount of ASGNA among transgenic plants reached approximately 6.5 μg/g fresh weight. A feeding bioassay showed that survival and reproductive rates of aphids fed transgenic tissues were significantly lower than those fed wild type tissues. Likewise, larvae mortality of P. xylostella fed with transgenic plants showed significantly increased levels. Similar results were recorded of aphids feeding on cotton cotyledons with transient expression of ASGNA. Conclusions: Altogether, results show that ASGNA exhibited high insecticidal activity towards sap-sucking insects and is a promising candidate gene to improve insect resistance in cotton and other dicot plants.