Bacterially expressed dsRNA induces Varroa destructor gene knockdown by honey bee-mediated oral administration

Abstract

The ectoparasite Varroa destructor causes serious losses of Apis mellifera colonies and negatively impacts the beekeeping industry around the world. New control methods have been proposed based on the RNA interference technique. Previous reports showed that parasitized honey bees fed with double-stranded RNA (dsRNA) synthesized in vitro reduce the transcription levels of target genes in Varroa mites. An efficient and inexpensive alternative to produce dsRNA is the use of bacteria capable of achieving high levels of in vivo synthesis. In the present study, dsRNA synthetized in vivo was used to induce gene silencing in V. destructor and evaluate their effect on the survival of both honey bees and the parasitic Varroa mites. The results evidenced that dsRNA fed to the bees engendered gene silencing in mites, inhibiting expression levels of target genes by 50%. Indeed, a reduction of 50% in Varroa survival was observed when bacterially expressed dsRNAs were administered to mite-parasitized bees. Worker bees that were fed with Varroa-targeted dsRNA by oral route showed no survival differences compared to control bees, fed with sucrose or dsRNA-GFP solutions. Our results demonstrated that specific dsRNA over-expressed in bacteria is capable of reducing mite survival by bee-mediated oral administration. This study provides an efficient and low-cost method for dsRNA production to control parasites and honey bee diseases.

Keywords:

• Varroa destructor
• honey bees
• gene silencing
• in vivo dsRNA synthesis

Acknowledgments

We thank Lucas Landi and Pablo Nakaya for their assistance with honey bee colony management. On behalf of all authors, we would like to thank Dr. M.A. Palacio and Dr. G.A. Rodriguez for their support during the planification of the bioassays.

Disclosure statement

No potential competing interest was reported by the authors.

Additional information

Funding

This study was funded by Instituto Nacional de Tecnología Agropecuaria (INTA) through the National Program of Apiculture through Grant 1112042. We are grateful for the financial support of the Agencia Nacional de Promoción Científica y Tecnológica of Argentina (through the project Foncyt PICT 2016-0221 to ACS and MCL), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (through the project PIP 2015-0517CO to ACS).