Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [24]
Once the sequence data can be used to identify functional genes, it should be possible to detect which genes are responsible for, say, successful transmission of the microorganisms that carry disease inside the mosquito's body, or for the mosquito's ability to use odor cues in sweat or exhaled breath to find a human to bite. The hope then is to tinker with these genes and breed a mosquito with a gut that is inhospitable to the malaria parasite, or one that cannot smell a delectably pungent victim nearby. Genes that are used to resist the effects of insecticides could similarly be altered to ensure that the mosquitoes remain vulnerable to certain chemicals.
If the fruit flies were sequenced to take advantage of the classic model system for genetics, and mosquitoes were sequenced in hopes of applying the knowledge to curing human disease, the flour beetle Tribolium castaneum could be said to have been sequenced because, well, no project in animal biology is complete without including a beetle. More kinds of beetles have been described than any other single group of animals—with over 350,000 species, one-quarter of all of the species of animals in the world is a type of beetle. The scientists who collaborated to sequence the flour beetle genome boast that beetles are "by far the most evolutionarily successful" multicelled organisms, and list, as if the insects were trying out for some kind of all-star reality television show, the many talents found in the group: "Beetles can luminesce, spit defensive liquids, visually and behaviorally mimic bees and wasps, or chemically mimic ants." I am not sure why these particular abilities are showcased, although there is a kind of "animals you might want with you on a desert island" kind of flavor to the selection. Interestingly, the beetles share with that other highly successful insect group, the ants, a lack of flight in day-to-day life; although most beetles can fly if necessary, their lives are mainly spent walking and tunneling on the ground. Whether this sacrifice of fragile wings is the key to their profligacy is not clear.
Tribolium itself is a good choice, among all those hard-shelled crawling candidates. Because it is easy to rear in large numbers in Petri dishes or other small containers, it has already been the subject of other types of genetic studies for many years. It is also an economically important pest in stored grains, which means that discoveries about its genome could reveal genetic Achilles heels to be exploited in its control, an urgent need since up to now it resists all kinds of insecticides that have been used against it.
Despite all the attention paid to the fruit fly Drosophila and its kin, it turns out that Tribolium is more of an "ur-insect," so to speak, than the fly—in other words, the flour beetle's genes seem to be less specialized and more like that of the ancestor of the entire class of insects than do the Drosophila genes. Over 125 groups of genes that the beetle has in common with humans, for example, don't occur in the other insects whose genomes had been sequenced as of 2009, suggesting that Tribolium has some pretty basic genetic material. In fact, nearly half of its genes are ancient, with counterpart genes occurring in vertebrates. This primordial nature means that it will be easier to determine how genes have changed through evolutionary time by comparing various groups to the Tribolium, and to determine which genes are responsible for general features of insect biology, such as metamorphosis or molting, and which are more idiosyncratic, say, those controlling the ability to make honey.
As is the case for genome size, and for that matter body shape and appearance, the genetic