Martin-Hernandez, R. | Search bioRxiv

bioRxiv2026

Genetic Diversity of Cytochrome P450 Genes in Apis mellifera Subspecies

The western honey bee (Apis mellifera) is an essential pollinator facing unprecedented threats from pesticide exposure. While pesticide resistance evolution is well documented in agricultural pests, our understanding of genetic variation in honey bee detoxification systems remains limited. This represents a missed opportunity, as harnessing naturally occurring detoxification diversity could provide new avenues for pollinator protection. Cytochrome P450 monooxygenases (CYPs), which are central to xenobiotic metabolism, offer a promising starting point. Here, we present the first comprehensive analysis of CYP genetic diversity in A. mellifera. We analysed the CYPome of 1,467 individuals representing 18 A. mellifera subspecies from 25 countries and identified 5,756 single-nucleotide polymorphisms (SNPs) in 46 CYP genes. Imputed McDonald-Kreitman testing revealed that 56% of non-synonymous CYP substitutions were driven by positive selection. Of the 1,302 haplotypes identified, 84% resided in CYP3, concentrated in the CYP9 and CYP6AS subfamilies implicated in xenobiotic detoxification. Population-level analysis of nucleotide diversity, Tajimas D selection signatures, FST-based differentiation, and McDonald-Kreitman testing pointed to CYP3 clan genes as the primary locus of adaptive variation. This work provides the first step toward building a comprehensive pharmacogenomic resource for honey bees, enabling the prediction of population-specific pesticide vulnerabilities and leveraging naturally occurring detoxification variants to enhance pollinator resilience - a critical step toward sustainable pollinator management.

genomics↗

bioRxiv2021

First description of Lotmaria passim and Crithidia mellificae haptomonad stage in the honeybee hindgut

The remodelling of flagella into attachment structures is a common and important event in the insect stages of the trypanosomatid life cycle. Among their hymenopteran hosts, Lotmaria passim and Crithidia mellificae can parasitize Apis mellifera, and as a result they might have a significant impact on honeybee health. However, there are details of their life cycle and the mechanisms underlying their pathogenicity in this host that remain unclear. Here we show that both L. passim promastigotes and C. mellificae choanomastigotes differentiate into haptomonad stage covering the ileum and rectum of honeybees. These haptomonad cells remain attached to the host surface via zonular hemidesmosome-like structures, as revealed by Transmission Electron Microscopy. Hence, for the first time this work describes the haptomonad morphotype of these species and their hemidesmosome-like attachment in Apis mellifera, a key trait exploited by other trypanosomatid species to proliferate in the insect host hindgut. Author summaryIn recent years, the mortality of European Honeybees (Apis mellifera) has risen worldwide due to a variety of factors, including their infection by parasites. Former studies have linked the presence of several trypanosomatids species, being Lotmaria passim and Crithidia mellificae the most prevalent ones, with this increase in mortality. Although previous studies have shown that trypanosomatid infection reduces the lifespan of bees, there is little information regarding their development in the gut when honeybees become infected. Here, for the first time we describe the haptomonad morphotype of these two trypanosomatid species in A. mellifera. The most characteristic feature of haptomonads is the extensive remodelling of the flagellum and the formation of junctional complexes at the host gut wall. The presence of this morphotype in the honeybee hindgut increases our understanding of the life cycle of these species and their possible pathogenic mechanisms. We found that they can multiply while attached and that their disposition, covering the hindgut walls, could hinder host nutrient uptake and consequently, represent a pathogenic mechanism itself. This attachment could also be a key stage in the life-cycle to prevent the trypanosomatids leaving the host prematurely, ensuring transmission through infective morphotypes.

pathology↗