Disruption of vitellogenin gene function in adult honeybees by intra-abdominal injection of double-stranded RNA

Abstract Background The ability to manipulate the genetic networks underlying the physiological and behavioural repertoires of the adult honeybee worker (Apis mellifera) is likely to deepen our understanding of issues such as learning and memory generation, ageing, and the regulatory anatomy of social systems in proximate as well as evolutionary terms. Here we assess two methods for probing gene function by RNA interference (RNAi) in adult honeybees. Results The vitellogenin gene was chosen as target because its expression is unlikely to have a phenotypic effect until the adult stage in bees. This allowed us to introduce dsRNA in preblastoderm eggs without affecting gene function during development. Of workers reared from eggs injected with dsRNA derived from a 504 bp stretch of the vitellogenin coding sequence, 15% had strongly reduced levels of vitellogenin mRNA. When dsRNA was introduced by intra-abdominal injection in newly emerged bees, almost all individuals (96 %) showed the mutant phenotype. An RNA-fragment with an apparent size similar to the template dsRNA was still present in this group after 15 days. Conclusion Injection of dsRNA in eggs at the preblastoderm stage seems to allow disruption of gene function in all developmental stages. To dissect gene function in the adult stage, the intra-abdominal injection technique seems superior to egg injection as it gives a much higher penetrance, it is much simpler, and it makes it possible to address genes that are also expressed in the embryonic, larval or pupal stages.

We appreciate the help of M Beye and M Hasselmann in producing vitellogenin dsRNA, and of AM Nascimento on 33P hybridizations for visualizing small RNA fragments by Northern blot. We also thank A Hagen for technical assistance. We are grateful to K Hartfelder and MJA da Rocha for generous support and critical discussions. We thank G Hunt and K Hartfelder for helpful comments on the manuscript. GVA's contribution was financially supported by the Norwegian Research Council, project no. 133680/110.

We appreciate the help of M Beye and M Hasselmann in producing vitellogenin dsRNA, and of AM Nascimento on 33P hybridizations for visualizing small RNA fragments by Northern blot. We also thank A Hagen for technical assistance. We are grateful to K Hartfelder and MJA da Rocha for generous support and critical discussions. We thank G Hunt and K Hartfelder for helpful comments on the manuscript. GVAs contribution was financially supported by the Norwegian Research Council, project no. 133680/110.