Overview

This project will quantify, for the first time, the genetic and epigenetic effects of long term neonicotinoid exposure on bumblebee populations.  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. This project will identify the selection in response to this pressure We have previously found epigenetic effects due to acute exposure of neonicotinoids. Recent work in evolutionary biology suggests that the heritable epigenetic system can respond rapidly to selectional pressures.

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 eighty genes with differential methylation due to neonicotinoid exposure.

Probably Maurice Maeterlinck not Einstein.

Methodology

Using the PUSSTAT database identify three matched pairs of sites; sites routinely exposed to neonicotinoids over the last two decades and control site not exposed. From these sites collect twenty samples per site. Half of each homogenized bee will be used to make BS-RADseq libraries and the other half to make the RAD-seq libraries. The RADseq data will be analysed to look for selection in response to neonicotinoid exposure. The BS-RADseq will be analysed to look for long term epigenetic changes due to neonicotinoid exposure.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research  themes. 

The student will be provided with training, as required, in R, a powerful and increasing popular statistical programming language, Python, a general-purpose, high-level programming language widely used in bioinformatics, molecular biology and bee husbandry.

Timeline

Year 1:  Collecting samples from the fieldsites.. Production and sequencing of libraries. Begin analysis.

Year 2: Complete analysis of BS-RAD-seq and RAD-seq libraries. Publish resultant papers.

Year 3: Explore other avenues opened by previous two years. For example candidate gene approach and common garden experiments to examine the evolution of tolerance in bees in the field exposed to neonicontinoids.

Partners and collaboration (including CASE)

This is a collaborative project between the lead supervisor Mallon and co-supervisor Rosato. The supervisors have complimentary interests and expertise in ecotoxicology and social insects and of next generation sequencing techniques to investigating these areas.  Mallon will provide specific expertise in the role of epigenetics and gene expression, while Rosato provides expertise in ecotoxicology and candidate gene molecular biology. This proposal will benefit greatly from the ongoing collaboration between M and R in co-supervising a current PhD student working on bumblebees.

Further Details

Please contact Eamonn Mallon, Department of genetics and genome biology, University of Leicester, ebm3@le.ac.uk for further details.