Abstract
Securing food supply for a growing population is a major challenge and heavily relies on the use of agrochemicals to maximize crop yield. It is increasingly recognized, that some neonicotinoid insecticides have a negative impact on non-target organisms, including important pollinators such as the European honeybee Apis mellifera. Toxicity of neonicotinoids may be enhanced through simultaneous exposure with additional pesticides, which could help explain, in part, the global decline of honeybee colonies. Here we examined whether exposure effects of the neonicotinoid thiamethoxam on bee viability are enhanced by the commonly used fungicide carbendazim and the herbicide glyphosate. We also analysed alternative splicing changes upon pesticide exposure in the honeybee. In particular, we examined transcripts of three genes: (i) the stress sensor gene X box binding protein-1 (Xbp1), (ii) the Down Syndrome Cell Adhesion Molecule (Dscam) gene and iii) the embryonic lethal/abnormal visual system (elav) gene, which are important for neuronal function. Our results showed that acute thiamethoxam exposure is not enhanced by carbendazim, nor glyphosate. Toxicity of the compounds did not trigger stress-induced, alternative splicing in the analysed mRNAs, thereby leaving dormant a cellular response pathway to these man-made environmental perturbations.
Highlights
Worldwide honeybees and other insects encounter new man-made compounds at potentially harmful concentrations in agricultural landscapes
Thiamethoxam toxicity in bees is not enhanced by carbendazim and glyphosate
The commonly used fungicide carbendazim and herbicide glyphosate, both at highest water soluble concentrations of 2 mM and 32 mM were not lethal (Fig. 1)
Summary
Worldwide honeybees and other insects encounter new man-made compounds at potentially harmful concentrations in agricultural landscapes. The combinatorial use of many herbicides, fungicides and pesticides is increasingly recognized for having a negative impact on many pollinators including the honeybee Apis mellifera[1,2]. During their foraging for nectar, pollen and water, forager bees can be exposed to agrochemicals which have been applied to crops[3,4]. Through the contaminated food harvested by bees and brought into the hive, the entire colony can be exposed to complex cocktails of xenobiotics[5] Such exposure to sub-lethal mixtures of pesticides may cause a reduction in vigour and productivity of the hive[5,6]. This intron is spliced through a mechanism normally operative in tRNA genes leading to expression of the full length Xbp[1] transcription factor, which triggers the UPR
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