| MicroRNAs(miRNAs)are a class of naturally occurring,small non-coding RNA molecules,approximately 19-24 nucleotides(nt)in length.In eukaryote,miRNAs negatively regulate gene expression at the post-transcriptional level by directly targeting the 3’-untranslated region(3’-UTR)of mRNA and thereby inhibiting protein expression or causing the degradation of mRNA.miRNA exits in plant,animal,fungi,bacteria and virus,which play roles in many biological process,such as cell proliferation,cell metabolism,developmental transition and lipornetabolism.Recent studies have showed that miRNA not only function in the original cells but also can communicate in different cell types.Besides,some stricking findings suggest that miRNAs can be transmitted from one species to another and regulate genes in different species.The paper we published before reported an unexpected finding that plant miRNAs which are ingested from plant foods can pass through the gastrointestinal tract,enter into the blood,accumulate in tissues and regulate endogenous gene expression in animals.In this paper,we investigated the role of plant miRNAs playing in honeybee caste differentiation.Honeybee caste formation is assumed to be determined by larval nutrient status:royal jelly stimulates the differentiation of larvae into queen,whereas beebread leads to worker bee fate.Here,we reported that plant RNA particularly miRNAs,which were significantly enriched in beebread than royal jelly,delayed development and decreased body and ovary size in honeybees,thereby preventing larval differentiation towards queens but inducing worker bees.Plant RNA and miRNA also led Drosophila larvae to develop into adults similar to worker bee phenotype,characterized by extended developmental time and reductions in body weight and length,ovary size and fecundity.Mechanistic studies revealed the amTOR gene that plays a stimulatory role in caste differentiation was the direct target of MIR 162a.Taken together,this study identified a previously uncharacterized function of plant miRNAs in larval food to fine-tune caste diffrentiation,which offer valuable hints for understanding cross-kingdom interaction.In summary,we identified far more enriched plant miRNAs in beebread and pollen rather than royal jelly and we provided the evidence that regulation of the worker bee caste may be attributable to a previously uncharacterized effect executed by the enriched plant miRNAs in beebread and pollen to young larvae.In this study,we first proved that plant miRNAs play role in honeybee caste differention and further demonstrated the function of exogenous miRNAs in animals. |
