A Transmissible RNA Pathway in Honey Bees.

Systemic RNAi, initiated by double-stranded RNA (dsRNA) ingestion, has been reported in diverse invertebrates, including honey bees, demonstrating environmental RNA uptake that undermines homologous gene expression. However, the question why any organism would take up RNA from the environment has remained largely unanswered. Here, we report on horizontal RNA flow among honey bees mediated by secretion and ingestion of worker and royal jelly diets. We demonstrate that transmission of jelly-secreted dsRNA to larvae is biologically active and triggers gene knockdown that lasts into adulthood. Worker and royal jellies harbor differential naturally occurring RNA populations. Jelly RNAs corresponded to honey bee protein-coding genes, transposable elements, and non-coding RNA, as well as bacteria, fungi, and viruses. These results reveal an inherent property of honey bees to share RNA among individuals and generations. Our findings suggest a transmissible RNA pathway, playing a role in social immunity and signaling between members of the hive.

PAP1 transcription factor enhances production of phenylpropanoid and terpenoid scent compounds in rose flowers.

• Floral scent is a complex trait of biological and applied significance. To evaluate whether scent production originating from diverse metabolic pathways (e.g. phenylpropanoids and isoprenoids) can be affected by transcriptional regulators, Arabidopsis PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1) transcription factor was introduced into Rosa hybrida. • Color and scent profiles of PAP1-transgenic and control (ß-glucuronidase-expressing) rose flowers and the expression of key genes involved in the production of secondary metabolites were analyzed. To evaluate the significance of the scent modification, olfactory trials were conducted with both humans and honeybees. • In addition to increased levels of phenylpropanoid-derived color and scent compounds when compared with control flowers, PAP1-transgenic rose lines also emitted up to 6.5 times higher levels of terpenoid scent compounds. Olfactory assay revealed that bees and humans could discriminate between the floral scents of PAP1-transgenic and control flowers. • The increase in volatile production in PAP1 transgenes was not caused solely by transcriptional activation of their respective biosynthetic genes, but probably also resulted from enhanced metabolic flux in both the phenylpropanoid and isoprenoid pathways. The mechanism(s) governing the interactions in these metabolic pathways that are responsible for the production of specialized metabolites remains to be elucidated.

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

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.