The Genome of an Agricultural Pest
The red flour beetle, a widespread pest in flour mills, silos, and pantries, has become the fourth insect–and the first significant agricultural pest–to have its genome sequenced. The work should give scientists an even better understanding of insect biology, development, and evolution, and help them develop new ways of controlling the voracious beetle.
“Maybe we can make a more selective insecticide,” says project leader Stephen Richards, assistant professor in the Baylor College of Medicine Human Genome Sequencing Center.
The ubiquitous beetle–Tribolium castaneum–has been “found in every inhabited place on earth, everywhere people live and store grain,” says Richard Beeman, a research entomologist with the U.S. Department of Agriculture, who worked on the beetle project. However, there’s currently no effective way of controlling the beetle because it has developed resistance to all the chemicals that have been deployed to fight it.
Many insects have evolved the ability to detoxify chemicals used against them–both those produced naturally as a defense by plants, and insecticides used in pest control. But it’s often difficult to figure out how they do it, says Barry Pittendrigh, an associate professor in the Department of Entomology at Purdue University, who was not involved in the sequencing work. But the sequencing project could help: scientists identified a number of enzymes that enable it to break down various insecticides. The research was published Sunday in an advance online version of the journal Nature.
The sequencing work may also help researchers figure out new ways of combating the beetle by targeting genes that affect vital processes like digestion and the formation of the insect’s exoskeleton. “That’s one of the big hopes and promises of the genome project,” says Beeman. The researchers, for example, found more than 100 genes that are important in the synthesis of the beetle’s tough but flexible exoskeleton, providing “a huge number of potential targets,” for pest control, he says.
A better understanding of how the exoskeleton is formed might also have applications in materials science. “Just imagine a football helmet made of insect chitin,” Beeman says.
The sequencing work, which cost $3 to $4 million, is part of an effort to analyze the genetic codes of model organisms in order to better understand their biology, as well as the human genome. The red flour beetle is the first beetle to have its genome sequenced; the only other insects to share that honor are the fruit fly, the honeybee, and the malaria-carrying mosquito.
The beetle consortium used the high-throughput sequencing facilities at Baylor College of Medicine to sequence the insect’s 16,000 genes–a fairly small genome for an insect, Beeman says. The researchers also manually analyzed about 2,000 of the beetle’s genes, focusing on those that are important in development and in pesticide resistance.
The beetle is an ideal subject for genetic work because it’s easily cultured and amenable to RNA interference, which involves inserting double-stranded RNA corresponding to a particular gene into an organism so that the gene is knocked out. “We can ask, what does that beetle look like without that gene working?” Richards says.
Researchers also uncovered clues to the beetle’s ability to withstand very dry conditions–down to as little as 10 percent humidity–like those found in grain storage facilities. The researchers found a gene for the receptor for vasopressin, a hormone that regulates water storage. It’s the first time that such a gene has been found in a sequenced insect, and it presumably helps the beetle survive in arid conditions, the researchers say. The gene shares the same ancestry as the vasopressin gene in humans.
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