Epigenetic effects of neonicotinoid pesticides on the important pollinator, the buff tailed bumble bee, Bombus terrestris

This project will quantify, for the first time, the epigenetic effects of neonicotinoids on bumblebees, by examining treated bees’ methylomes and transcriptomes. The social epigenetics lab at the University of Leicester has pioneered the study of bumblebee epigenetics. Neonicotinoid insecticides have been strongly implicated in the decline of bees affecting a number of important biological functions; an exciting possibility is that they do this by affecting the methylation system of bees.

The role of insect pollinators in feeding a growing population and their recent declines is explicitly mentioned in NERC’s “The business of the environment” (page 5). This project fits into two NERC research areas; 1) Ecotoxicology - Diagnostics, tolerance and adaption in relation to natural and anthropogenic toxic substances and 2) Environmental genomics - Understanding the response of organisms to their natural environment at the level of the genome.

Neonicotinoids are effective insecticides used on many important crops, often as seed dressing. They are systemic, meaning they are absorbed by the plant and transported to all tissues where they remain active for many weeks. However, their tissue distribution and stability, which are important for their efficacy, determines their lack of species-specificity and their negative effects on the environment. In 2013 the European Union imposed a partial restriction on their use.

Laboratory and field studies have found effects on the behaviour, mortality and colony performance of bees exposed to neonicotinoids. The effects are so broad as to be likely caused by mechanisms additional to the primary toxicity, namely the block of the nicotinic acetylcholine receptors (nAChRs) resulting in major dysfunction of neuronal transmission. In mice, nicotine reduces DNA methylation in AChRs cells suggesting epigenetic consequences following repeated activation of nAChRs.

Methylation, the addition of a methyl group to a cytosine, has important effects on the biology of bees, including the control of reproductive status, task switching and memory. Methylation affects gene expression and alternative splicing in social insects. In a small preliminary BS-seq we found over thirty genes with differential methylation due to neonicotinoid exposure.