Project description:Epigenetic modifications are known to profoundly affect the development and behavior of social insects. In the well-known caste differentiation process of honeybee (Apis mellifera), female larvae with identical genomes are fed royal jellydifferently and develop into either normal workers or into very large, long-lived, and extremely fecund queens, and the queen-worker asymmetry of honeybee is known to be result largely to differential genomic imprinting during larval development that involves DNA methylation-based regulation. The discovery of reversible N6-methyladenosine (m6A) RNA methylation modification has defined a new era for RNA-metabolism-related genetic regulation, yet much remains unknown about m6A-mediated post-transcriptional regulatory mechanisms. Here, we report the first honeybee RNA m6A methylome. Specifically, we used the m6A-seq technique to examine the RNA m6A methylomes of honeybee larvae, including queen and worker larvae at multiple instar stages. We identified multiple conserved features of m6A methylation machinery and transcriptome-wide m6A distribution trends among insect species, and observed that m6A marks exert functions in regulating caste differentiation, with apparently particularly strong functional impacts on fifth instar worker larvae. Functional annotation of differentially methylated candidate caste-differentiation-related transcripts revealed many known regulators of caste differentiation (e.g. ILP-2, p110, PI3K, and JHAMT etc.) as well as the widely-studied Vitellogenin gene, which has not previously been implicated in caste differentiation. As ever-more regulatory roles for m6A marks are discovered, honeybees may become an excellent model studying the biology of such epi-transcriptomic regulatory systems, from embryonic development through holometabolous caste-specific development and on towards behavior and the emergent social hierarchies underlying eusociality in animals.
Project description:The major environmental determinants of honeybee caste development come from larval nutrients: royal jelly stimulates the differentiation of larvae into queens, whereas beebread leads to worker bee fate. However, these determinants are not fully characterized. Here we report that plant RNAs, particularly miRNAs, which are more enriched in beebread than in royal jelly, delay development and decrease body and ovary size in honeybees, thereby preventing larval differentiation into queens and inducing development into worker bees. Mechanistic studies reveal that amTOR, a stimulatory gene in caste differentiation, is the direct target of miR162a. Interestingly, the same effect also exists in non-social Drosophila. When such plant RNAs and miRNAs are fed to Drosophila larvae, they cause extended developmental times and reductions in body weight and length, ovary size and fecundity. This study identifies an uncharacterized function of plant miRNAs that fine-tunes honeybee caste development, offering hints for understanding cross-kingdom interaction and coevolution.
Project description:Our aim was to identify the genes that are responsible for caste differentiation in the primitively eusocial bumble bee, Bombus terrestris. To do this we extracted RNA from both queen- and worker-destined larvae. We extracted RNA from three key stages during bumble bee development (before, during, and after their caste becomes fixed), and then sent the sequencing to the Earlham Institute. They used mRNAseq to isolate the RNA from each developmental stage and caste pathway.
Project description:Honeybees are very important eusocial insects and are involved in the pollination of many plants. Queen bees and worker bees develop from the same fertilized eggs, and are thus genetically identical despite their substantial behavioural and physiological differences. The mechanism governing developmental differences between worker and queen bees has always attracted much interest. While there are several reports on mRNA expression related to caste differentiation, no systematic investigation of small RNAs has thus far been carried out. Results: Using deep sequencing we systematically profiled small RNA expression in 4th-6th day worker larvae and queen larvae (the critical stages at which the fates of workers and queens are determined), and found that 38 miRNAs were differentially expressed between worker and queen larvae. In addition, 639 mature miRNA candidates were identified in our work for the first time, of which, 526 were expressed only in workers (318) or queens (208). Conclusion: We present the first profile of honeybee small RNAs and explore the mechanism of caste differentiation between worker and queen bees. Caste-specific expression patterns and large discrepancies in small RNA profiles between worker and queen bees indicate that small RNAs may be related to the differential development of worker and queen bee larvae. Results presented here will make a valuable contribution to understanding the caste switch between worker and queen bees.