Researchers from Heinrich Heine University Düsseldorf have identified a key gene and the molecular mechanism associated with determining the sex of bees. In a study published in the scientific journal Science Advances, the researchers describe how this process is similar to a game involving two dice.
The sex of an organism has significant implications for its form, function, and behavior. While humans have a sex-determining “Y chromosome,” bees have a different mechanism. In 1845, Silesian priest Johann Dzierzon examined the sex-determining mechanisms of honeybees and discovered the asexual reproduction of male bees, known as “drones.”
Unlike humans, bees do not have just one sex-determining chromosome. The research team, led by Professor Dr. Martin Beye, found that sex in bees is determined by a single gene called “Csd” (Complementary sex determiner) through a unique mechanism. This gene can have over 100 variations, or alleles, similar to how different alleles of a gene can determine petal color in flowers.
During sexual fertilization, the chromosomes from the egg and sperm cells combine, resulting in a diploid chromosome set. This means that each sexually fertilized bee has two variants of the Csd gene. The researchers discovered that when the two alleles of the Csd gene are different, a female bee develops. On the other hand, if the gene alleles are the same on both chromosomes, a male bee develops. However, worker bees do not raise the eggs of male bees to prevent inbreeding.
The research team also investigated the molecular mechanism behind this sex determination process. They found that each allele of the Csd gene produces a slightly different variant of the associated Csd protein. Only different Csd proteins can bind with each other and activate a molecular switch that determines the development of a female bee. If the Csd proteins are the same, they bind differently, and the switch is not activated, resulting in the development of a male bee that is not raised by worker bees.
Dr. Marianne Otte, the lead author of the study, explained that the Csd protein’s switch function was the key to solving a genetic mystery that has existed for over 100 years. Professor Beye mentioned that further research is needed to understand how worker bees identify whether a fertilized egg contains two different Csd proteins. He suggested that there might be an olfactory clue inside the hive.
The findings of this study will contribute to advancements in bee breeding measures. Understanding the genetic mechanisms behind bee sex determination can help beekeepers and researchers develop strategies for efficient bee breeding and conservation.
Reference:
“Recognition of polymorphic Csd proteins determines sex in the honeybee” by Marianne Otte, Oksana Netschitailo, Stefanie Weidtkamp-Peters, Claus A. M. Seidel, and Martin Beye, 4 October 2023, Science Advances.
DOI: 10.1126/sciadv.adg4239