Insecticidal fern proteins protect genetically modified cotton from pests

Cotton farmers have a fight to pick with whiteflies. The sap-sucking insects stunt crop growth, and their sticky excrement fosters detrimental fungal infections. Whiteflies also carry hoards of viruses that can wipe out entire fields. Farmers often plant genetically modified (GM) crops including corn, soybeans, and cotton that produce their own insecticides called Bt toxins. But whiteflies are unfazed by Bt toxins, leaving cotton fields defenseless. That inspired Pradhyumna Kumar Singh of India’s National Botanical Research Institute to search for an alternative. Noticing that whiteflies rarely bother fern plants, he screened 38 fern species to uncover natural insecticides against the whitefly species Bemisia tabaci. Singh and colleagues discovered a protein in the edible fern Tectaria macrodonta that they named Tma12. When inserted into cotton plants, the Tma12 gene provided resistance to more than 99% of the whitefly population while leaving ladybugs—natural predators of whiteflies and aphids—unharmed. Toxicity studies in rats found no adverse effects from Tma12 exposure (Nat. Biotechnol. 2016, DOI: 10.1038/nbt.3665). The authors note that “the absence of known allergenic motifs suggests that Tma12 might be a promising candidate for the development of GM crops.”