Thiamethoxam exposure deregulates short ORF gene expression in the honey bee and compromises immune response to bacteria

Pamela Decio, Pinar Ustaoglu, Kamila Derecka, Ian C. W. Hardy, Thaisa C. Roat, Osmar Malaspina, Nigel P. Mongan, Reinhard Stoger, Matthias Soller

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Maximizing crop yields relies on the use of agrochemicals to control insect pests. One of the most widely used classes of insecticides are neonicotinoids that interfere with signalling of the neurotransmitter acetylcholine, but these can also disrupt crop-pollination services provided by bees. Here, we analysed whether chronic low dose long-term exposure to the neonicotinoid thiamethoxam alters gene expression and alternative splicing in brains of Africanized honey bees, Apis mellifera, as adaptation to altered neuronal signalling. We find differentially regulated genes that show concentration-dependent responses to thiamethoxam, but no changes in alternative splicing. Most differentially expressed genes have no annotated function but encode short Open Reading Frames, a characteristic feature of anti-microbial peptides. As this suggested that immune responses may be compromised by thiamethoxam exposure, we tested the impact of thiamethoxam on bee immunity by injecting bacteria. We show that intrinsically sub-lethal thiamethoxam exposure makes bees more vulnerable to normally non-pathogenic bacteria. Our findings imply a synergistic mechanism for the observed bee population declines that concern agriculturists, conservation ecologists and the public.
Original languageEnglish
Article number1489
JournalScientific Reports
Issue number1
Publication statusPublished - 15 Jan 2021

Bibliographical note

Funding Information:
We thank N. Parker and the Winterbourne garden for bees, N. Parker for bee suits, D. Scocchia, V. Soller-Haussmann and K. Nallasivan for help with bee collections. G. Salmond for bacterial strains, D. Scocchia for help with bacterial culturing and genotyping, and L. Orsini, E. Davies and I. Haussmann for comments on the manuscript. For this work we acknowledge funding from the Foundation for Research Support of the State of São Paulo, FAPESP (2012/13370-8; 2013/07251-9; 2014/23197-7; 2015/22368-5), the Biotechnology and Biological Sciences Research Council (BBSRC), the Nottingham-Birmingham Fund, and the Sukran Sinan Memory Fund.


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