Bidirectional transfer of RNAi between honey bee and Varroa destructor: Varroa gene silencing reduces Varroa population.

Yael Garbian,Eyal Maori,Sharoni Shafir,Ilan Sela,Haim Kalev,David S Schneider

doi:10.1371/journal.ppat.1003035

Abstract

The mite Varroa destructor is an obligatory ectoparasite of the honey bee (Apis mellifera) and is one of the major threats to apiculture worldwide. We previously reported that honey bees fed on double-stranded RNA (dsRNA) with a sequence homologous to that of the Israeli acute paralysis virus are protected from the viral disease. Here we show that dsRNA ingested by bees is transferred to the Varroa mite and from mite on to a parasitized bee. This cross-species, reciprocal exchange of dsRNA between bee and Varroa engendered targeted gene silencing in the latter, and resulted in an over 60% decrease in the mite population. Thus, transfer of gene-silencing-triggering molecules between this invertebrate host and its ectoparasite could lead to a conceptually novel approach to Varroa control.

Highlights

The European honey bee, Apis mellifera, plays a key role in pollination
We show that double-stranded RNA (dsRNA) ingested by honey bees is further transmitted to the parasitic mite Varroa destructor that feeds on the honey bee’s hemolymph
We demonstrate that bees ingesting dsRNA of Varroa gene sequences become vectors of dsRNAs, transmitting the signals to the Varroa, engendering silencing of mite genes and resulting in a significant phenotype, Varroa mortality

Summary

Introduction

The European honey bee, Apis mellifera, plays a key role in pollination. One third of the world’s food crops as well as many wild plants depend on honey bees for pollination [1]. Honey bee colonies suffer from severe losses worldwide. Varroa destructor is an obligatory parasite that feeds on the hemolymph of developing and mature honey bees. When the adult bee emerges, the attached female mites emerge with it. Honeybee colonies infested with Varroa destructor typically collapse within 2 to 3 years [3,10]. Beekeepers use chemicals such as the organophosphate coumaphos, tau-fluvalinate and the formamidine amitraz to control Varroa, but the mites evolve resistance to such chemicals [11,12,13,14]. We report that Varroa gene expression can be modulated by RNA interference (RNAi) mediated by the bees, which may lead to a potential new conceptual approach to Varroa control

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Conclusion