We’d all like to be queen for a day, but most of us weren’t born into royalty. In the honey bee world, your queen status is also determined pretty early on—only 96 hours after hatching. New research has uncovered more epigenetic modifications that determine who gets to be queen bee. And who better to study queens than a team out of Queen Mary University in London. Led by Marek Wojciechowski and Robert Lowe, the talented team investigated histone post-translational modifications (PTMs) in the two female honey bee castes: the worker caste and the queen caste. Here they identify novel caste-specific chromatin patterns, and correlate them with caste-specific gene expression and development.
This team must have been busier than bees as they set out to look at three major histone PTMs (H3K4me3, H3K27ac and H3K36me3) across both worker and queen bee genomes at 96 hours after hatching. Using a combination of Chromatin Immunoprecipitation (ChIP) to sequence chromatin and RNA-seq to correlate transcriptional differences, here’s what they found:
- H3K4me3, H3K36me3, and H3K27ac exhibit caste-specific distributions
- Enrichment of H3K4me3 and H3K36me3 corresponds with increased gene transcription
- Gene Ontology (GO) analysis reveals differential expression of caste-specific genes, favoring growth and metabolic processes in the queen and nervous system development in the worker
- Both chromatin enrichment patterns and differential transcription of genes suggest that the queen bee developmental trajectory is already established 96 hours after hatching, whereas the worker bee trajectory is not
- In the worker caste, H3K27ac is more abundant in intronic regions, which are also enriched in transcription factor binding motifs.
- This correlates with increased gene expression, indicating that H3K27ac may mark active enhancer regions in the worker caste
Reiterating the importance of histones, co-senior senior author Paul Hurd commented, “The ability of an individual larva to become a worker or a queen is due to the way genes are switched on or off in response to the specific diet. [Histones] control both structural and functional aspects of the organism’s genetic material and have the capacity to determine which part of the genome, and when, has to be activated to respond to both internal and external stimuli.” Co-senior author Ryszard Maleszka concludes, “The extent of histone modifications uncovered by this study was remarkable and exceeded our expectations.”
To see what the buzz is all about, read the full article at Genome Research, August 2018.