Impact of Proteins Used in Plant Genetic Engineering: Toxicity and Behavioral Study in the Honeybee

Abstract

Genetically modified oilseed rape, Brassica napus L., expressing pest and fungi resistance has been assessed for its impact on the environment before field testing and placing on the market. The evaluation of rape lines for their inocuousness to beneficial insects such as the honeybee, Apis mellifera L., were investigated because changes in the composition of nectar and pollen may occur that affect plant-honeybee interactions. The effects of these plants on bees were evaluated by acute toxicity testing of the gene products and behavioral studies of bees. Acute toxicity was determined by evaluating the mortality over 24- and 48-h periods after ingestion or injection of the gene products. For the bee behavioral study, methods used to study learning processes and foraging behavior were adapted to test the effect of the gene products at both individual and colony levels under confined conditions. The study focused on the effects of proteins inducing resistance to pest insects, cowpea trypsin inhibitor (CpTI), and resistance to fungi, chitinase, and β-1,3 glucanase. Under our experimental conditions, the 3 proteins were shown to be nontoxic at the doses tested. At the individual level, behavior experiments, based on a conditioned proboscis extension response, had the following 3 effects depending on the protein tested; (1) chitinase did not affect learning performance; (2) β-1,3 glucanase affected the level of conditioned responses, with the extinction process occurring more rapidly as the concentration increased; and (3) CpTI induced marked effects in both conditioning and testing phases, especially in high concentrations. The decrease in learning performance induced by CpTI observed at the individual level was confirmed at the colony level. Given their relative simplicity, it is suggested that such bioassays could be used for screening in the development of genetically modified plants.