Gene expression in Carniolan honey bee (Apis mellifera carnica) exposed to pesticides
1 University of Ljubljana, Biotechnical Faculty, Department of Animal Science, Groblje 3, SI-1230 Domzale, Slovenia
2 University of Ljubljana, Biotechnical Faculty, Department of Biology, Vecna pot 111, SI-1000 Ljubljana, Slovenia
The Carniolan honey bee, Apis mellifera carnica, is important pollinator to diverse agricultural crop plants in Slovenia. Intensive agriculture depends on the use of plant protection products that can have negative effects even on non-target organisms, including honey bees. Since 2006 losses of honey bee colonies all over the world concern beekeepers and agriculture producers. Pathogens, parasitic mites and exposure to pesticides have been investigated as potential causes of honey bee death. There are three main routes of honey bee exposure to pesticide: (i) exposure from residues in nectar and pollen in the flowers of treated plants; (ii) exposure from dust produced during the sowing of treated seeds or application of granules; (iii) and exposure from residues in guttation fluid produced by treated plants. Moreover, pesticide could have an impact via pollen consumption not only on foraging honey bees but also on entire honey bee colony. The role of pesticide and their sub-lethal doses are subjects of an increasing number of studies. It is known that prolonged exposure to pesticides weaken the immune defence mechanisms of bees and increase sensitivity to certain chemicals. Separate pesticide could not be highly toxic to bees but combination of two or even more of different pesticides might lead to higher honey bee sensitivity or mortality. In our study we investigated the molecular response of honey bee workers exposed (a) to the insecticide thiamethoxam and the fungicide mancozeb and (b) to the acaricide coumaphos and the fungicide prochloraz. Expression of immune-, development- and detoxification-related genes was examined by quantitative RT-PCR. Negative impacts of pesticides and/or their combinations differed between each treatment. All combinations of pesticides up-regulated the expression of majority of immune-related genes. The expression of development-related genes (hexamerin 70B and vitellogenin) was down-regulated in honey bees treated with thiamethoxam and mancozeb, while in the expression of hexamerin 70B was up-regulated in coumaphos and prochloraz treated honey bees. Some of the detoxification‑related genes were up-regulated and some of them were down-regulated, depending on pesticides that were used. Our results clearly show the negative effect of pesticides on honey bees at the molecular level.