{"id":200571,"date":"2025-06-20T18:47:10","date_gmt":"2025-06-20T18:47:10","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/200571\/"},"modified":"2025-06-20T18:47:10","modified_gmt":"2025-06-20T18:47:10","slug":"how-a-genetic-tug-of-war-decides-the-fate-of-a-honey-bee","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/200571\/","title":{"rendered":"How a genetic tug-of-war decides the fate of a honey bee"},"content":{"rendered":"

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Queen bees emit a pheromone that attracts worker bees \u2014 the queen’s daughters \u2014 to her side. The differentiation of bee larvae into either workers or queens has baffled researchers, and now a team led by researchers at Penn State has revealed the molecular mechanism underpinning this genetic mystery.\u00a0<\/p>\n

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Credit: Sean Bresnahan<\/p>\n

UNIVERSITY PARK, Pa. \u2014 Despite having identical genetic instructions, female honey bee larvae can develop into either long-lived reproductive queens or short-lived sterile workers who help rear their sisters rather than laying their own eggs. Now, an interdisciplinary team led by researchers at Penn State has uncovered the molecular mechanisms that control how the conflict between genes inherited from the father and the mother determine the larva\u2019s fate.<\/p>\n

They published their findings this week (June 18) in\u00a0Genome Biology<\/a>.<\/p>\n

\u201cImagine if your mother’s genes and your father’s genes were in constant disagreement about how you should develop \u2014 that is essentially what genomic imprinting is, and we see that it happens across the tree of life: from honey bees to humans,\u201d said Sean Bresnahan, the lead author of the study who conducted the study as a doctoral candidate in the\u00a0Interdisciplinary Graduate Degree Program in Molecular, Cellular, and Integrative Biosciences<\/a>\u00a0in the Huck Institutes of the Life Sciences at Penn State. Supported by a U.S. National Science Foundation (NSF) Graduate Research Fellowship at the time, Bresnahan graduated in 2024 and is now a data scientist at the University of Texas MD Anderson Cancer Center. \u201cWe found that this genetic \u2018argument\u2019 can be detected during a critical developmental window where a honey bee larva becomes either a queen or a worker.\u201d<\/p>\n

That critical window closes and the bee\u2019s fate becomes irreversible 192 hours after the egg is laid. To distinguish between patrigenes \u2014 genes inherited from the father \u2014 and matrigenes \u2014 genes inherited from the mother, study co-author Kate Anton, a research technologist in the\u00a0Center for Pollinator Research<\/a>\u00a0at Penn State, used instrumental insemination to create specific genetic crosses between selected queens and male bees, known as drones. The researchers worked with the\u00a0Penn State Genome Research Incubator\u00a0<\/a>to analyze the larvae\u2019s RNA, which contains and uses inherited genetic information to create proteins and support cellular activity, and identify the genes that were expressed differently between the two groups. The researchers also sequenced the parents\u2019 genomes and used genetic markers to trace parent-of-origin gene expression in the larvae, meaning they could see how gene expression differed depending on whether the gene was from the mother or father.<\/p>\n

\u201cWe found patrigenes were expressed at higher levels in queen-destined larvae, and matrigenes were expressed at higher levels in worker-destined larvae,\u201d Bresnahan said.<\/p>\n

The researchers then examined cellular and physiological pathways to determine if the genes showing parent-of-origin expression were functioning in the same pathway.<\/p>\n

\u201cWe saw a striking match between the expression of matrigenes and patrigenes in the same pathway,\u201d Bresnahan said, explaining that if a matrigene had increased expression then a patrigene would have decreased expression in the same pathway, or vice versa, showing that the two genes were working against each other. \u201cIf one gene showed parent-specific expression, another gene in the same pathway showed parent-specific expression from the opposite parent.\u201d<\/p>\n

Previously, the team examined whether DNA methylation \u2014 a process in which protein tags change how a gene is expressed without altering the underlying DNA \u2014 was the molecular mechanism underlying these differential gene expression patterns.<\/p>\n

\u201cIn mammals and plants, differential expression in imprinted genes \u2014 genes where only the information inherited from one parent is expressed \u2014 is typically mediated by differences in DNA methylation in the regulatory regions, where specific DNA sequences control expression, of these genes,\u201d said study co-author, Christina Grozinger, Publius Vergilius Maro Professor of Entomology and director of the Huck Institutes of the Life Sciences. \u201cBut our previous work found that DNA methylation does not have this function in honey bees.\u201d<\/p>\n

The researchers then turned to the idea that it may not be tags on the DNA that influence gene expression in honey bees, but rather tags on the structures around which DNA packages itself.\u00a0\u00a0 DNA is wound around histone proteins, in a structure called chromatin. During cellular reproduction, chromatin condenses into chromosomes. Typically developing multicellular organisms inherit equal numbers of chromosomes from each parent, providing the pool of genes from which an organism\u2019s specific genetic composition is made up. The team hypothesized that changes in the structure of histone proteins \u2014 due to chemical \u201ctags\u201d placed on the tails of the proteins as the result of cellular processes \u2014 could make the patrigenes and matrigenes more or less accessible to other regulatory factors. Such control could potentially change their expression.<\/p>\n

To test this hypothesis, the team used a method developed by study co-author, Shaun Mahony, associate professor in the\u00a0Center for Eukaryotic Gene Regulation<\/a>\u00a0and the Department of Biochemistry and Molecular Biology at Penn State. The process involves fragmenting DNA that is bound to a protein \u2014 histone proteins, in this case \u2014 and then using antibodies that are specific to the tagged proteins to capture and isolate these from the rest of the chromatin. Researchers can then analyze the DNA crosslinked to the captured protein and determine which genes are involved and whether they are expressed or inhibited.<\/p>\n

\u201cWe found that, in honey bees, parent-of-origin expression is regulated by histone modifications,\u201d Bresnahan said.<\/p>\n

He explained that the chemical tags modifying the histone proteins appears to mediate whether patrigenes or matrigenes are expressed and, ultimately, whether a honey bee becomes a queen or a worker. While the underpinning mechanism is not DNA methylation like the researchers initially thought, Bresnahan said it\u2019s not a surprising finding.<\/p>\n

\u201cWhat we’re seeing in honey bees isn’t actually that unusual when you take a step back \u2014 histone-based mechanisms for parent-of-origin effects are more widely utilized across the tree of life than DNA methylation-based systems,\u201d Bresnahan said. \u201cWe see these chromatin-mediated imprinting mechanisms in flowering plants and in placental mammals as well. So, honey bees, and maybe other social insects, might be using the more ancestral toolkit for mediating these genetic conflicts.\u201d<\/p>\n

This understanding could potentially help selectively breed for honey bees with different behaviors and traits, which could help produce more productive and resilient bee colonies, according to Grozinger, who said her lab plans to study how intragenomic conflict influences how well a subset of honey bees, called nurse bees, rear young bees, among other traits.<\/p>\n

Bresnahan said the project expands beyond honey bees, as the skills learned for this project translate to his current work. In his new role, Bresnahan continues to explore how genetic conflicts shape complex traits and social systems \u2014 but he\u2019s now focused on how the placenta mediates traits for maternal-child health in humans.<\/p>\n

\u201cThe skills I developed studying parent-of-origin effects translate directly to my current studies of maternal-child health mediated through the placenta,\u201d Bresnahan said. \u201cI am particularly interested in parent-of-origin gene expression associated with placenta-mediated traits, like early-life programming of metabolic and neuropsychiatric disease risk, that could help us better understand pregnancy complications and offspring health outcomes.\u201d<\/p>\n

Brock Harpur, associate professor of entomology at Purdue University also contributed to this study. The U.S. National Science Foundation, the U.S. Department of Agriculture National Institute of Food and Agriculture and Hatch Appropriations, the Publius Maro Professorship and the Huck Institutes of the Life Sciences supported this work.<\/p>\n

Article Title<\/p>\n

Intragenomic confict associated with extreme phenotypic plasticity in queen-worker caste determination in honey bees (Apis mellifera)<\/p>\n

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