Effects of dsRNA-GFP as exogenous control on honey bee RNAi assays: gene expression changes in workers

A green fluorescence protein (GFP)-derived dsRNA (dsRNA-GFP) has been used as an exogenous control for Apis mellifera RNAi assays by multiple research groups. Its sequence does not share any significant homology with any known honey bee genes. Although dsRNA-GFP is not expected to trigger an RNAi response in treated bees, undesirable effects on gene expression, pupal pigmentation or developmental timing have been routinely observed. To better understand the multiple molecular and phenotypic effects of dsRNA-GFP in honey bees and to evaluate its use as a control for RNAi studies, we examined the impact of dsRNA-GFP on global gene expression patterns in developing workers. We found that dsRNA-GFP causes large-scale changes in gene expression associated with multiple biological processes. Furthermore, dsRNA-GFP exposure tended to preferentially decrease, rather than increase, expression of genes compared to controls. Gene expression differences were analyzed using a dye-swap design. Second instar worker larvae received 0.5 μg of dsRNA-GFP. Non-treated and dsRNA-GFP treated 7 day-old workers (W7d) were sampled.