Transcriptome profiling of the honeybee parasite Varroa destructor provides new biological insights into the mite adult life cycle

Abstract

BackgroundThe parasite Varroa destructor represents a significant threat to honeybee colonies. Indeed, development of Varroa infestation within colonies, if left untreated, often leads to the death of the colony. Although its impact on bees has been extensively studied, less is known about its biology and the functional processes governing its adult life cycle and adaptation to its host. We therefore developed a full life cycle transcriptomic catalogue in adult Varroa females and included pairwise comparisons with males, artificially-reared and non-reproducing females (10 life cycle stages and conditions in total).ResultsExtensive remodeling of the Varroa transcriptome was observed, with an upregulation of energetic and chitin metabolic processes during the initial and final phases of the life cycle (e.g. phoretic and post-oviposition stages), whereas during reproductive stages in brood cells genes showing functions related to transcriptional regulation were overexpressed. Several neurotransmitter and neuropeptide receptors involved in behavioural regulation, as well as active compounds of salivary glands, were also expressed at a higher level outside the reproductive stages. No difference was detected between artificially-reared phoretic females and their counterparts in colonies, or between females who failed to reproduce and females who successfully reproduced, indicating that phoretic individuals can be reared outside host colonies without impacting their physiology and that mechanisms underlying reproductive failure occur before oogenesis.ConclusionsWe discuss how these new findings reveal the remarkable adaptation of Varroa to its host biology and notably to the switch from living on adults to reproducing in sealed brood cells. By spanning the entire adult life cycle, our work captures the dynamic changes in the parasite gene expression and serves as a unique resource for deciphering Varroa biology and identifying new targets for mite control.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4668-z) contains supplementary material, which is available to authorized users.

Deformed wing virus type A, a major honey bee pathogen, is vectored by the mite Varroa destructor in a non-propagative manner

“…Detection mainly included the genomic positive strand DWV RNA (Supplementary Data Table S1). RT-qPCR was carried out essentially as previously described 28,39 , DWV RNA copy numbers were log-transformed prior to statistical analyses. Negative-strand DWV RNA quantification was carried using two sets of primers designed for targeting different regions in the DWV genome, Assay 1 (region 4909-5008 nt) 16 and Assay 2 (region 7303-7503 nt) 40 .…”

A gene for resistance to the Varroa mite (Acari) in honey bee (Apis mellifera) pupae

“…As well as being involved in the initiation of pupation in honey bees, ecdysone and its derivatives also act as a trigger for vitellogenesis in the Acari (Cabrera et al, ; Mondet et al, ; Roe, Donohue, Khalil, & Sonenshine, ). Like many specialized parasites, Varroa exhibits reduced metabolic pathways even when compared to other parasitic Acari and Arthropods (Cabrera et al, ; Grbić et al, ).…”

Varroa chemosensory proteins: some are conserved across Arthropoda but others are arachnid specific

“…The Varroa genome is estimated as 565 Mbp, but consists of short and mostly unannotated sequences (Cornman et al, 2010;Campbell et al, 2015). Recently, transcriptomic and proteomic analysis by us and others showed differential expression in the different developmental stages of the adult mite, emphasizing the profound modifications taking place thorough the mite's life cycle (Eliash et al, 2017;Mondet et al, 2018). The aim of the present research focuses on the Varroa chemosensory machinery by comparing transcriptomic and proteomic profiles between the forelegs (at different physiological stages) and the rear legs.…”

“…However, very little is known regarding chemosensing in non-insect arthropods such as ticks and mites, despite their economic and agricultural significance. Nonetheless, in recent years, data on Chelicerata have begun to accumulate, mostly from genomic, transcriptomic and proteomic studies (Gulia-Nuss et al, 2016;Hoy et al, 2016;Iovinella et al, 2016;Vizueta et al, 2016;Eliash et al, 2017;Mcafee et al, 2017;Renthal et al, 2017;Mondet et al, 2018). These studies have revealed potential homologues of some of the known insect chemosensory protein families, based on sequence similarities.…”