Genetic Conflict Defines Role of Honey Bee Larvae: Queens vs. Workers

In a groundbreaking study, researchers from Penn State University have unveiled the intricate genetic mechanisms that dictate whether honey bee larvae develop into queens or workers. Published on June 18, 2025, in the journal *Genome Biology*, this research highlights the role of parental gene conflict in shaping the destinies of these vital pollinators.

The study, led by Sean Bresnahan, a former doctoral candidate in the Interdisciplinary Graduate Degree Program in Molecular, Cellular, and Integrative Biosciences, reveals that identical genetic instructions can lead to divergent developmental outcomes based on the interplay between genes inherited from the mother and father. "Imagine if your mother's genes and your father's genes were in constant disagreement about how you should develop — that is essentially what genomic imprinting is, and we see that it happens across the tree of life: from honey bees to humans," Bresnahan stated.

Honey bee larvae, depending on their genetic makeup and the timing of environmental cues, can mature into either reproductive queens or sterile workers. The researchers discovered that this pivotal decision occurs within the first 192 hours after an egg is laid. To investigate the underlying genetics, the team utilized instrumental insemination to create specific genetic crosses between selected queens and drones, enabling them to analyze the RNA of the larvae and discern differences in gene expression based on parental origin.

Kate Anton, a research technologist at the Center for Pollinator Research at Penn State, was instrumental in this phase of the research. The findings illustrated that genes inherited from the father, or patrigenes, were more actively expressed in larvae destined to become queens, while genes from the mother, or matrigenes, showed higher expression in those destined to be workers. This pattern indicates a genetic tug-of-war, where the expression of one parent’s genes can suppress the other’s in shared biological pathways.

Further investigation revealed that this genetic conflict is not mediated by DNA methylation, a common mechanism in mammals, but rather by modifications to histone proteins that package DNA. "We found that, in honey bees, parent-of-origin expression is regulated by histone modifications," Bresnahan explained. This novel understanding of gene expression in honey bees could have broader implications, suggesting that similar histone-based mechanisms might be at play in other species as well.

Christina Grozinger, the Publius Vergilius Maro Professor of Entomology and director of the Huck Institutes of the Life Sciences, noted that these insights could inform selective breeding strategies aimed at enhancing bee productivity and resilience. Additionally, Bresnahan indicated that his current research at the University of Texas MD Anderson Cancer Center builds upon these findings, as he explores how genetic conflicts influence maternal-child health outcomes in humans, particularly in the context of placental development.

This research not only sheds light on the complex dynamics within honey bee colonies but also emphasizes the broader implications of parental gene interactions across species. The intricate balance of genetic expression in determining roles within social structures could offer valuable insights into the evolution of cooperation and conflict in both bees and other organisms. As the study unfolds, the potential for applications in agriculture and health continues to expand, fostering a deeper understanding of the genetic foundations that govern life.