Impact of neonicotinoids on gene expression and synaptic plasticity in bee brains

Abstract

Pollination by Apis mellifera is extremely important ecologically as well as in agriculture securing food production worth billions worldwide. Recently bee populations have been declining described as Colony Collapse Disorder - CCD - for which the exact causes are not known. Xenobiotic compounds, such as thiamethoxam introduced in agro ecosystems e.g. as seed protectant, have been linked to CCD as they are toxic to bees causing mass disappearance of colonies in several countries. Thiamethoxam is extremely active in the insect nervous system, acting as an agonist of acetylcholine. Therefore, this study aims to evaluate the acute oral toxicity of thiamethoxam to Africanized Apis mellifera and investigate how the brain of these insects reacts to the intoxication by sublethal doses of thiametoxam. In particular, we expect that toxic insult will result in changes of gene expression of important neuronal genes such as splicing regulators and a consequence result in changes of alternative splicing of ion channels and mediators of synaptic function. These studies will be complemented by ultra-structural examination of changes in synaptic patterns by immunolocalization of the protein synapsing and spatial distribution of the proteins present in the brain by Maldi-imaging technique. These techniques, together, will provide information about which brain structures are affected by thiamethoxam, which suggest possible physiological and behavioral consequences that such exposure may cause to the insect. This study can contribute to clarify whether such insecticides would be among the causes of the Colony Collapse Disorder - CCD currently. (AU)