Comparative transcriptomics indicates endogenous differences in detoxification capacity after formic acid treatment between honey bees and varroa mites

Abstract

Formic acid (FA) has been used for decades to control Varroa destructor, one of the most important parasites of the western honey bee, Apis mellifera. The rather unselective molecular mode of action of FA and its possible effects on honeybees have long been a concern of beekeepers, as it has undesirable side effects that affect the health of bee colonies. This study focuses on short-term transcriptomic changes as analysed by RNAseq in both larval and adult honey bees and in mites after FA treatment under applied conditions. Our study aims to identify those genes in honey bees and varroa mites differentially expressed upon a typical FA hive exposure scenario. Five detoxification-related genes were identified with significantly enhanced and one gene with significantly decreased expression under FA exposure. Regulated genes in our test setting included members of various cytochrome P450 subfamilies, a flavin-dependent monooxygenase and a cytosolic 10-formyltetrahydrofolate dehydrogenase (FDH), known to be involved in formate metabolism in mammals. We were able to detect differences in the regulation of detoxification-associated genes between mites and honey bees as well as between the two different developmental stages of the honey bee. Additionally, we detected repressed regulation of Varroa genes involved in cellular respiration, suggesting mitochondrial dysfunction and supporting the current view on the mode of action of FA—inhibition of oxidative phosphorylation. This study shows distinct cellular effects induced by FA on the global transcriptome of both host and parasite in comparison. Our expression data might help to identify possible differences in the affected metabolic pathways and thus make a first contribution to elucidate the mode of detoxification of FA.

Influence of formic acid treatment on the proteome of the ectoparasite Varroa destructor

“…The FMO GS-OXs are considered to be a specific enzyme group of cruciferous plants (Brassicaceae) and catalyze the first structural modification step in the synthesis of aliphatic glucosinolates [ 78 , 79 ]. In contrast to this and also in contrast to the results of a distinct FMO5 transcript analysis [ 80 ], the results of the protein expression analysis showed a significantly reduced concentration of another FMO, FMO5 . FMOs represent a family of enzymes that metabolise xenobiotic compounds in the so-called phase I [ 81 – 83 ].…”

Behavioral and genetic correlates of heterogeneity in learning performance in individual honeybees,Apis mellifera

“…In addition, confirmatory expression analyses were also performed for selected transcripts using RT-qPCRs according to the previously published protocols. [63] [64]. Primers are listed in Supplementary Table 1 (S1) and Actin was chosen as reference gene (TIB Molbiol, Berlin, Germany).…”

Varroa destructor from the Laboratory to the Field: Control, Biocontrol and IPM Perspectives—A Review

“…It inhibits the oxidative phosphorylation, thus impacting the mitochondrial energy metabolism [ 116 ]. Genath et al, (2020) [ 117 ] studied the transcriptome of A. mellifera and V. destructor after topical formic acid treatment and highlighted a difference in detoxification capacity between the host and the acari. Their work supports the hypothesis of interference with cellular respiration through the modified expression of several genes like cytochrome P450 suggesting a stronger toxic selectivity toward the mite.…”