The NHGRI published a high-quality draft genome sequence of the Western honey bee, finding that its genome is more similar to humans than either of the other two insects sequenced thus far.
The honey bee's social behavior makes it an important model for understanding how genes regulate behavior through the development of the brain and central nervous system. That may lead to insights into common mental and brain disorders, such as depression or schizophrenia or Alzheimer's disease. Moreover, the bee genome may also provide a window into immunity and aging.
In a paper published in the October 26 issue of Nature, the Honey Bee Genome Consortium, led by Richard Gibbs, Ph.D., director of the Human Genome Sequencing Center at Baylor College of Medicine (BCM-HGSC) in Houston, describes the approximately 260 million DNA base pair genome of the honey bee (Apis mellifera). Although only 9% the size of the 3 billion base pairs in the human genome, the honey bee contains nearly half as many genes as the human genome, more than 10,000 in the bee compared to around 20,000 genes in the human.
The other two insects that have been sequenced are the malaria-carrying mosquito (Anopheles gambiae), completed in 2002, and the fruit fly (Drosophila melanogaster), an extensively used model organism in genetics research completed in 2000. The honey bee genome is 50% larger than fruit flies but contains roughly the same number of genes.
In the analysis, the researchers report that the honey bee has evolved more slowly than the fruit fly or mosquito and contains 10,157 known genes. Researchers caution that this gene count will increase as other insects are sequenced and compared to the honey bee in the future.
When compared to other insects, the honey bee genome contains fewer genes involved in innate immunity, detoxification enzymes, and gustatory receptors. It contains more genes for olfactory receptors and novel genes for nectar and pollen utilization. Interestingly, the honey bee genome shows greater similarities to vertebrates than insects for genes involved in circadian rhythm, as well as biological processes involved in turning genes on or off.
Researchers discovered nine genes in the royal jelly protein family, which appear in the honey bee genome but not the mosquito genome. These genes have gained new functions through evolution and are believed to contribute to the sociality of the honey bee. Royal jelly is produced by glands in the head of adult worker bees and an important nutritional component in queen and brood care. This process is vital in the early development of a honey bee and determines whether it becomes a queen or an altruistic worker.
All organisms' genomes contain common types of transposons, small DNA sequences that move around in a genome that can cause mutations, but there are substantially fewer transposons in the honey bee genome. To understand why the honey bee has so few transposons, researchers will need to obtain genomes from insects more closely related to honey bee than the insect genomes that already have been studied.
While the honey bee shares similar genes with other insects in developmental pathways, there is a dramatic difference in how these genes influence sex determination, brain function and behavior. In most organisms, high fertility is achieved at the expense of lifespan. This process is regulated by a gene for insulin-like growth factor. However, researchers discovered that queen honey bees are able to achieve high fertility without affecting their lifespan. Future experiments studying this biological pathway could uncover how this process has been modified in the honey bee giving insights into human reproduction and human aging.