Variable induction of vitellogenin genes in the varroa mite, Varroa destructor (Anderson & Trueman), by the honeybee, Apis mellifera L, host and its environment

Abstract

Transcript levels of vitellogenins (Vgs) in the varroa mite, Varroa destructor (Anderson & Trueman), were variably induced by interactions between the developing honeybee, Apis mellifera L, as a food source and the capped honeybee cell environment. Transcripts for two Vgs of varroa mites were sequenced and putative Vg protein products characterized. Sequence analysis of VdVg1 and VdVg2 proteins showed that each had greater similarity with Vg1 and Vg2 proteins from ticks, respectively, than between themselves and were grouped separately by phylogenetic analyses. This suggests there was a duplication of the ancestral acarine Vg gene prior to the divergence of the mites and ticks. Low levels of transcript were detected in immature mites, males and phoretic females. Following cell invasion by phoretic females, VdVg1 and VdVg2 transcript levels were up-regulated after cell capping to a maximum at the time of partial cocoon formation by the honeybee. During oviposition the two transcripts were differentially expressed with higher levels of VdVg2 being observed. A bioassay based on assessing the transcript levels was established. Increases in VdVg1 and VdVg2 transcripts were induced experimentally in phoretic females when they were placed inside a cell containing an early metamorphosing last instar bee but not when exposed to the metamorphosing bee alone. The variable response of Vg expression to the food source as well as environmental cues within the capped cell demonstrates that perturbation of host-parasite interactions may provide avenues to disrupt the reproductive cycle of the varroa mites and prevent varroasis.

A selective sweep in a Varroa destructor resistant honeybee (Apis mellifera) population

“…Vitellogenines are proteins produced in the fat body and are taken up by the maturing oocytes. During embryogenesis vitellin (glycosylated vitellogenin) contained in the yolk is a very important source of nutrients (Cabrera Cordon et al, 2013). The sensing of nutrients taken up due to a blood meal occurs via the target of rapamycin (TOR) signalling pathway, which is a regulatory network that controls cellular activity according to nutrient availability and is essential for the yolk protein precursor (YPP) expression in mosquitoes (Hansen et al, 2004) and ticks (UmemiyaShirafuji et al, 2012).…”

Flowers promote ovarian development and vitellogenin gene expression in Apolygus lucorum (Heteroptera: Miridae)

“…It is important to understand the inherent mechanisms of well-developed ovary of A. lucorum fed by plant flowers, this information also will facilitate the artificial rearing of this species and better understand the ecological significance of the flower preference of the adults. In insects, vitellogenesis is the central event supporting egg development, and the yolk is the main source of nutrition for future embryos (Kawakami et al 2009;Cabrera Cordon et al 2013). For example, reduced Vg production in the planthopper Nilaparvata lugens resulted in undeveloped ovaries with Vg depletion in the basal oocyte and smaller ovarioles as well as infertility .…”

A feeding protocol for delivery of agents to assess development in Varroa mites

“…These nine genes were selected based on previous work assessing differential transcription during the mite reproductive phase [33, 34, 59, 60]. Total RNA was isolated from these samples using the RNeasy Mini Kit (Qiagen Inc.), following the manufacturer’s recommendation.…”

“…Initiation of oogenesis is observed within 6 h after cell capping [31, 32]. Vitellogenesis is initiated within 10 h after cell capping as the vitellogenin transcripts become elevated [33], the large lipid transfer protein (LLTP) transcripts are depressed [34] and yolk spheres can be observed accumulating within the oocyte [35]. The first egg is laid approximately 70 h after cell capping [32, 36] and is a haploid male [37].…”