Mitigating effects of pollen during paraquat exposure on gene expression and pathogen prevalence in Apis mellifera L

Abstract

Honey bee (Apis mellifera L.) populations have been experiencing notable mortality in Europe and North America. No single cause has been identified for these dramatic losses, but rather multiple interacting factors are likely responsible (such as pesticides, malnutrition, habitat loss, and pathogens). Paraquat is one of the most widely used non-selective herbicides, especially in developing countries. This herbicide is considered slightly toxic to honey bees, despite being reported as a highly effective inducer of oxidative stress in a wide range of living systems. Here, we test the effects of paraquat on the expression of detoxification and antioxidant-related genes, as well as on the dynamics of pathogen titers. Moreover, we tested the effects of pollen as mitigating factor to paraquat exposure. Our results show significant changes in the expression of several antioxidant-related and detoxification-related genes in the presence of paraquat, as well as an increase of pathogens titers. Finally, we demonstrate a mitigating effect of pollen through the up-regulation of specific genes and improvement of survival of bees exposed to paraquat. The presence of pollen in the diet was also correlated with a reduced prevalence of Nosema and viral pathogens. We discuss the importance of honey bees' nutrition, especially the availability of pollen, on colony losses chronically reported in the USA and Europe.

Ex Vivo Effect of Ibogaine on the Transcriptional Level of Antioxidant Defense Related Genes in Honey Bee (Apis mellifera, L.) Midgut

“…In our experiment, incubation with paraquat (10µg/mL) for 2 h provoked reactions on the transcriptional level, a significant increase of the Sod1 and Cat genes expression, as fundamentals mediators for ROS removal, while the expression of Nrf2 gene did not change significantly. These results are in agreement with de Mattos and coauthors [15] who showed significant correlation of Sod1 gene expression with the paraquat in honey bees, while Cat expression did not change in their study. The study about the effect of paraquat for 12 h in Drosophila melanogaster found its biphasic effect on the gene expression and enzyme activity of Sod1 and Cat with peak at 2.5 µM dose [18].…”

“…In order to verify the applicability of the midgut cells in primary tissue culture, as model system, we tested cell viability and cultivated the tissue with paraquat the most widely used non-selective herbicide. Despite being considered non-toxic to slightly toxic to adult bees [14], paraquat has been proven to be effective inducer of oxidative stress in this species [9,15]. Gut epithelial cells are of great importance for the insect health, involved in food digestion processes, but also as important component of innate immunity and local deference against microorganisms.…”

Effects of Dual Exposure to the Herbicides Atrazine and Paraquat on Adult Climbing Ability and Longevity in Drosophila melanogaster

“…For example, paraquat and the fungicide maneb affect stress response genes [35] and motor ability [27]. Heat stress [36] and diet [26] also interact with paraquat to affect survival. Several studies have found synergistic interactions between atrazine and organophosphate or pyrethroid insecticides on invertebrates [23,37,38].…”

“…In D. melanogaster , paraquat exposure reduces longevity [18,19,20], decreases dopaminergic neuron number [18,21], changes dopamine and dopamine metabolite levels [21], and alters motor functions [18,19,22]. Both atrazine and paraquat are known to interact with other environmental stressors [23,24,25,26,27]. To our knowledge, however, no other study has specifically examined the combined effects of atrazine and paraquat in vivo.…”

Bioaccumulation and Toxicity of Organic Chemicals in Terrestrial Invertebrates

“…For example, the pure active substance 2,4-dichlorophenoxyacetic acid (2,4-D) may upregulate superoxide dismutase, glutathione S-transferases, and catalase genes expression in Eisenia andrei [40], while siduron-based herbicides may induce downregulation of metallothionein and the expression of heat shock protein genes in E. fetida [41]. In the honey bee A. mellifera, paraquat may downregulate glutathione S-transferase, superoxide dismutase, and peroxiredoxin gene expression levels, but not those of catalase, cytochrome P450s, and vitellogenin genes [42].…”