Honey Bee Genome: Social Insect Creates Buzz For Agricultural, Biomedical Research

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 important insights into common mental and brain disorders, such as depression, schizophrenia or Alzheimer's disease. Moreover, the bee genome may also provide an important window into immunity and aging.

In a paper published in the Oct. 26 issue of Nature, the Honey Bee Genome Consortium, led by George Weinstock, Ph.D., co-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). Over 40 other companion manuscripts describing further detailed analyses are in current issues of Insect Molecular Biology, Genome Research, Science, Proceedings of the National Academy of Sciences (USA), and other journals.

"Comparing the genome of the honey bee with other species separated over evolutionary time from humans has provided us with powerful insights into the complex biological processes that have evolved over hundreds of millions of years," said NHGRI Director Francis S. Collins, M.D., Ph.D. "The genome of the honey bee has been added to a growing list of organisms whose sequence can be compared side by side to better understand the structure and functions of our own genes. And that will help speed our understanding of how genes contribute to health and what goes wrong in illness."

Although only 9 percent 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 honey bee is the third insect to have its genome sequenced and analyzed. The malaria-carrying mosquito (Anopheles gambiae) was completed in 2002 and the fruit fly (Drosophila melanogaster), an extensively used model organism in genetics research, was completed in 2000. The honey bee genome is 50 percent larger than fruit fly genome but contains roughly the same number of genes.

Sequencing of the honey bee genome began in early 2003. NHGRI provided about $6.9 million in funding for the project and the U.S. Department of Agriculture contributed $750,000. Additional support was provided by the National Institute of Allergy and Infectious Diseases (NIAID) and the National Library of Medicine (NLM), both components of the NIH.

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 (taste) receptors, while not surprisingly, 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.

Other findings from the Nature paper include:

* 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 is 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 the 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.

In addition to its value as a resource for comparative genomics, the honey bee is widely used in agricultural and biomedical research. The honey bee is valued by farmers for its ability to produce honey and pollinate crops. Beside its importance in agriculture, the honey bee serves as a model organism for studying human health issues including immunity, allergic reaction, antibiotic resistance, development, mental health, longevity and diseases of the X chromosome. The honey bee is also studied for its social instincts and behavioral traits.

After assembly of the genome at the BCM-HGSC, the center led an analysis team of more than 170 investigators representing nearly 100 research groups from 16 countries. Researchers deposited the initial assembly in 2004, based on 7.5-fold sequence coverage of the honey bee genome, into the NIH-run, public database, GenBank (www.ncbi.nih.gov/Genbank). In turn, Genbank distributed the sequence data to the European Molecular Biology Laboratory's Nucleotide Sequence Database, EMBL-Bank (www.ebi.ac.uk/embl/index.html), and the DNA Data Bank of Japan, DDBJ (www.ddbj.nig.ac.jp).