The mechanism for sex-determination in honeybees is one of the long-standing problems that geneticists and entomologists have been trying to solve for the past 200 years. Johann Dzierson, a Silesian monk who studied honeybee sex-determination in the mid-1800s, first stated the problem. While Dzierson proposed a probable mechanism, the solution was far from complete.
From Dzierson's initial studies he determined that the amount, as well as the quality of food given to a queen bee, had some effect on whether the queen produced eggs that would grow up to become either worker bees or queen bees. However, both worker and queen bees are female. While Dzierson's shed some light on the subject, techniques available at the time made it difficult to prove Dzierson's theories on male sex-determination. Moreover, understanding the genetic origins of the system proved impractical at the time.
A research team from the Arizona State University may have unlocked the key to solving the mystery of honeybee sex-determination. According to its findings, sex-determination in honeybee colonies is determined by 5 amino acids. These amino acids are the key to understanding the molecular switch that induces haplodiploidy in these bees. This condition, which is responsible for genetic sex-determination, is thought to have evolved slowly as a specialized adaptation for honeybees.
Dzierson was able to lay out a basic theory on how male honeybees came about. He theorized that the male half of this subset of bees only had one set of chromosomes, a condition known as "haploidy." Put simply, this means that male honeybees come from unfertilized eggs while female honeybees come from fertilized eggs. This theory was proven later when improvements to microscope technology came about. However, the question of how this strange sex-determination system evolved remained unsolved.
The Arizona State University paper, co-authored by Robert E. Page Jr., was able to decipher to mystery. The team studied 14 naturally occurring sequence variants in the complementary sex-determining switch. The study also extended across honeybee 76 genotypes, which resulted in the identification of the 5 amino acids said to control the process. The gene representing the control switch for the mechanism, called CSD, controls the femaleness of the egg. If the gene is suppressed, the honeybee egg becomes male.
