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Honeybee genome sequenced

Analysis finds social insects are more similar in some ways to vertebrates than to other insects

By | October 25, 2006

The genome sequence of the western honeybee may help explain the molecular and genetic basis of this insect's unusual sociality, according to the authors of the published sequence in this week's Nature. The Honeybee Genome Sequencing Consortium has completed the first draft of the sequence, as well as a spate of analyses covering the development, reproduction, gene regulation, neurobiology and behavior, and population genetics of the insect. The paper accomplishes for the honeybee "in a single package" what took more than a decade to produce for the fruit fly, said Sergey Nuzhdin of the University of California, Davis, who was not involved in the project. Besides assembling the genome sequence, the researchers "have managed to interpret genome information in a truly functional sense," Nuzhdin told The Scientist. The research teams cloned and sequenced more than 230 million bases of the Apis mellifera genome, leaving about 26 million bases, which lie in unclonable regions of the genome. They found that the honeybee genome is more A-T rich than other sequenced insects and contains an unusually small number of transposons. The honeybee genome also appears to have evolved more slowly than those of the fruit fly Drosophila melanogaster and the malaria mosquito Anopheles gambiae, making the honeybee much more closely related than the other two insects to humans. Honeybees "do things that are just really complicated that distinguish them from Drosophila and from mosquitoes," said principal investigator Richard Gibbs of Baylor College of Medicine in Houston. The scientists found that several types of honeybee genes are more similar to vertebrate genes than to other insect genes, including many involved in circadian rhythms,RNA interference, DNA methylation, and learning and memory. The authors also found many changes in gene number between honeybees and Drosophila, which they say may underlie the honeybee's distinctive social behavior. For example, honeybees have a larger family of genes for producing major royal jelly proteins, which are needed for brood feeding and for caste development between queens and workers. Honeybees also have greatly expanded families of odorant receptors, which they need to communicate via pheromones and to recognize flower types and family members. On the other hand, honeybees have a much smaller array of taste receptors than do fruit flies and mosquitoes, possibly because adults feed their larvae and rarely encounter toxins in their mutualistic relationships with flowers, the authors speculate. Honeybees also have novel genes involved in using nectar and pollen. Finding these types of genetic differences between honeybees and other insects is "really interesting, because it right away links genome evolution to the ecology of the animal," said Yehuda Ben-Shahar of the University of Iowa in Iowa City, who was not involved in the project. Some of the sequence analyses couldn't be easily explained, however. Honeybees have fewer innate immunity genes, which is a surprise, Gibbs said, since they live in colonies and therefore pass infectious pathogens among themselves. Also, honeybees possess genes similar to known Drosophila sex determination genes, even though honeybees have an entirely different mechanism of determining sex. According to the authors, exploring these paradoxes will "establish the honeybee as a new model for several fundamental processes of life." It's probably too early to say with certainty which gene families underlie social behaviors in the honeybee, Ben-Shahar told The Scientist. Sequencing other eusocial insects like termites or wasps may provide some insight into genes or regulatory regions important for insect sociality, but expecting to find similar genes underlying sociality in primates or dogs, for example, "might be a stretch," Ben-Shahar said. Finishing the sequence allows geneticists to study honeybee polymorphisms and "opens the door to really doing genetics in the organism," Gibbs told The Scientist. "To me, that's the most exciting thing." The Nature article appears simultaneously with related papers in Genome Research, PNAS and Science. Genome Research has devoted its entire issue to the biology of the honeybee, while articles in Science use the genome data to study the honeybee's vertebrate-like DNA methylation; to reveal the honeybee's evolutionary origins in Africa; and to identify neuropeptides that could aid in the study of the honeybee's sociality. Melissa Lee Phillips mphillips@the-scientist.com Links within this article: M.A. Watanabe, "Honeybee Sequencing: One Honey of an Idea," The Scientist, June 24, 2002. http://www.the-scientist.com/article/display/13120 The Honeybee Genome Sequencing Consortium, "Insights into social insects from the genome of the honeybee Apis mellifera," Nature 443:931-949, October 26, 2006. http://www.nature.com/nature/journal/v443/n7114/abs/nature05260.html Honeybee Genome Sequencing Consortium http://www.hgsc.bcm.tmc.edu/projects/honeybee Sergey Nuzhdin http://nlab.ucdavis.edu T.M. Powledge, "How many genomes are enough?" The Scientist, November 17, 2003. http://www.the-scientist.com/news/20031117/07 Richard Gibbs http://www.bcm.edu/cmb/?pmid=2207 G. Dutton, J.M. Perkel, "Shhh: Silencing Genes with RNA Interference," The Scientist, April 7, 2003. http://www.the-scientist.com/article/display/13678 S. Albert et al., "The family of major royal jelly proteins and its evolution," Journal of Molecular Evolution, August 1999. http://www.the-scientist.com/pubmed/10441680 Yehuda Ben-Shahar http://www.medicine.uiowa.edu/WelshLab/YBen-Shahar.htm C. Holding, "Evolution of innate immunity," The Scientist, July 8, 2004. http://www.the-scientist.com/article/display/22271 C. Holding, "Sex and the Honeybee," The Scientist, August 27, 2003. http://www.the-scientist.com/article/display/21550 E.O. Wilson et al., "Eusociality: origin and consequences," PNAS, September 20, 2005. http://www.the-scientist.com/pubmed/16157878
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Comments

Avatar of: Tom Wanamaker

Tom Wanamaker

Posts: 4

October 25, 2006

Your article about the honeybee genome contains the following: \n\n"The honeybee genome also appears to have evolved more slowly than those of the fruit fly Drosophila melanogaster and the malaria mosquito Anopheles gambiae, making the honeybee much more closely related than the other two insects to humans."\n\nThis inaccuracy is very misleading -- all insects are equally related (or unrelated, depending upon how you look at it) to humans and all other vertebrates. It would have been more accurate to say, "The honeybee genome is more similar to that of humans and other vertebrates," or , "Anopheles and Drosophila are more genetically different from vertebrates than the honeybee." \n\nInaccurate statements like this make it more difficult for people to understand and therefore accept evolutionary theory, thus making my job as a biology teacher more difficult.
Avatar of: David Bump

David Bump

Posts: 15

October 26, 2006

As the evolutionary biology teacher pointed out, it would be better to say that some genes have more or less similarity to those in mammals. For example, as another part of the study revealed, the circadian clock (and the relevant genes) of the honeybee are more like those in mammals than those in other insects, but this would be called "convergence." And as this article here indicates, there are other "paradoxes" in that they don't fit expectations based on posited evolutionary relationships.\n\nOf course, if evolution were true, a less-evolved insect would have changed less from the common ancestor with vertebrates, and so in that sense be more closely related to humans and other mammals. To illustrate with a case much closer and more obvious: If we discovered an ape that had evolved less than chimpanzees from our common ancestor (was more "primitive" or like a \n"living fossil"), we'd say it was more closely related to us, wouldn't we? \n\nMaybe evolutionary biology is so hard to teach because it's just a bunch of confusing, changing stories connecting dots of data in ways that can never be demonstrated to be true.
Avatar of: John Simkiss

John Simkiss

Posts: 1

November 2, 2006

Mr. Bump wrote:\n\n"Maybe evolutionary biology is so hard to teach because it's just a bunch of confusing, changing stories connecting dots of data in ways that can never be demonstrated to be true."\n\nA better explanation would be that it is hard to teach because people like yourself refuse to relinquish the creation myths that your parents told you were true and to never question.\n\nEvolution is a theory in the same sense that gravity is a theory. If the Bible contradicted the theory of gravity, would you jump off a tall building?\n\njas3\n\np.s. I'll arrange the gravity test for you at your convenience.

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