Posts Tagged: Walter Leal
Researchers in the Walter Leal lab, UC Davis Department of Entomology, are engaging in some exciting research.
They just discovered a "generic insect repellent detector" in the fruit fly (Drosophila melanogaster)--research published today (March 16) in PloS One (Public Library of Science).
What's exciting is that this research may lead to more effective and lower-cost products than DEET, the gold standard of insect repellents.
The five-member team found the sensory organs involved when fruit flies detect and avoid three key insect repellents: DEET, IR3535 and picaridin. They identified the olfactory receptor neuron (ORN) and characterized its receptor, DmOr42a.
The research team of Leal; primary author and chemical ecologist Zain Syed; chemical ecologist Julien Pelletier; and undergraduate students Eric Flounders and Rodrigo Chitolina, first found that the fruit fly avoids all three well-known repellents, DEET, IR3535 (a compound known as Avon Corporation’s “Skin-So-Soft Bug Guard”) and picaridin (derived from pepper) and then set out to find olfactory receptor neurons sensitive to those insect repellents. They scanned all olfactory sensilla in the antennae and the mouthpart structure, maxillary palps, using single unit electrophysiological recordings.
The receptor they found “fulfills the requirements for a simplified bioassay for early screening of test insect repellents,” they wrote in the scientific paper.
When you think that it takes about 10 years and $30 million to develop a new repellent--and only one test compound in 20,000 reaches the market--this could really speed up the process.
Zain Syed told us: "In this study, by using established behavioral assays to dissect the mechanism of repulsion in fruit flies, we demonstrated for the first time that Drosophila equally avoid other repellents--picaridin and IR3535. By challenging every type of olfactory sensilla on the antenna and maxillary palps, we identified neurons and then the odorant receptor that detect these repellents."
The UC Davis research, as Syed said, "adds a new dimension in research towards understanding the molecular, cellular and organismal response to repellents."
Chemical ecologist Coby Schal, the Blanton J. Whitmire Distinguished Professor of Entomology at North Carolina State University, praised the research as “an excellent example of translational research that can lead to a streamlined and less expensive path of discovery of new repellents.”
In earlier research, Syed and Leal identified a DEET-sensitive olfactory receptor neuron in the Southern House mosquito. “Going from the neuron to the receptor, however, is like looking for the proverbial needle in a haystack as the mosquito genome has some 181 olfactory receptor genes,” Schal said.
The Leal lab knows DEET. Back in August 2008, Leal and Syed drew international attention when they announced they'd discovered DEET’s mode of action or how it works. Scientists long surmised that DEET masks the smell of the host, or jams or corrupts the insect’s senses, interfering with its ability to locate a host. The Leal-Syed research showed that mosquitoes actually smell DEET and avoid it because they dislike the smell.
DEET, developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, is the go-to insect repellent. Worldwide, more than 200 million use DEET to ward off vectorborne diseases.
Leal, a chemical ecologist and professor of entomology, recently organized and moderated a symposium with professor John Hildebrand of the University of Arizona on "The Diversity in Olfaction and Taste" at the 58th annual Entomological Society of America (ESA) meeting.
Among the nine speakers at the San Diego conference: Bert Hoelldobler of Arizona State University who discussed "Communication and Social Organization Among Insects Via Chemical Cues"; Kristin Scott of UC Berkeley, "Taste Recognition in Drosophila (Flies)"; Julien Pelletier of UC Davis, "Conserved and Diverse Mosquito Odorant Receptors"; Hildebrand, "Olfactory Mechanisms Underlying Moth-Host Plant Interactions"; and Leal, who covered "Odorant Receptors from Moths, Flies and Mosquitoes." (Note the communication between a male and female silkworm moth in the accompanying photo by Samuel Woo of UC Davis.)
It's an exciting field--the field of olfaction and taste. And now the Leal lab has an opening for a postdoc trained in biochemistry/molecular biology to join a group of scholars (http://chemecol.ucdavis.edu/) investigating at the molecular level how insect perceive the world true small chemical molecules like pheromones, oviposition attractants, repellents, etc.
Leal, a fellow of the ESA and the American Association for the Advancement of Science and former president of the International Society for Chemical Ecology, is focusing his current research on the molecular basis of insect olfaction, with particular emphasis on odorant binding, release, and inactivation in the peripheral nervous system and chemical ecology.
Leal has published more than 150 papers in peer reviewed journals, 16 invited chapters and review articles, 28 Japanese patents and 2 US patents. Some of the recent publications:
Postdoc scholars who want to apply can email their CV and a letter of application to firstname.lastname@example.org.
That quote sound familiar? Chemical ecologist Jacques Le Magnen (1916-2002) said that back in 1970.
World-renowned organic chemist Wittko Francke (right) of the University of Hamburg, Germany, called attention to Le Magnen's quote at a UC Davis Department of Entomology seminar on Wednesday noon, Dec. 8.
It bears repeating: "Nature is more a world of scents than a source of noise."
Insects communicate in a chemical language or chemical signals, Francke told the crowd.
Indeed, scientists have long known that methods that can attract or repel insects have important applications for agricultural pests and medical entomology.
Francke told how a queen bee secretes compounds that regulate development and behavior of the colony, and how an orchid releases the scent of a female wasp to attract male wasps— a scent that results in pollination. He also touched on the “calling cards” of a number of other insects, including bumble bees, wasps, pea gall midges, stingless bees, bark beetles and leafminers. He pointed out that that plants, too, send chemical signals.
UC Davis graduate students James Harwood and Amy Morice of the James R. Carey lab video-taped the seminar. It will be online soon at http://entomology.ucdavis.edu/news/webcastlinks.html
Francke was introduced by chemical ecologist-forest entomologist (and UC Davis Department of Entomology affiliate) Steve Seybold of the USDA Forest Service, Pacific Southwest Research Station, Davis.
No stranger to UC Davis, Francke previously collaborated with chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology, on attractants for navel orangeworm.
In his talk, Francke mentioned Leal’s discovery of a sophisticated mechanism for the isolation of the chemical communication channels of two species of scarab beetles.
Seybold and Francke are collaborating on the chemical signals of the walnut twig beetle, which in association with a newly described fungus, causes thousand cankers disease, a killer of walnut trees.
Thousand cankers disease (TCD) is now found in seven western states, plus Tennessee. Seybold is a key researcher in California.
Scientists believe that TCD occurs only on walnut, predominantly native black walnut, Juglans californica and J. hindsii, although the disease has been recorded on 10 species of walnuts or their hybrids in California.
Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, said Seybold, who has been studying the chemical ecology and behavior of bark beetles for more than 25 years. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus.
A USDA/UC Davis research team is tracking the pathogen and the beetle throughout California, particularly in commercial orchards.
That all points back to “Nature is more a world of scents than a source of noise.”
They Deal with Scents
"He is slim and intense, with graying hair and clipped sentences jagged with inflections from his years in Brazil and Japan. And he does not, perhaps cannot, quit."
So wrote freelance journalist Carrie Peyton Dahlberg, formerly with the Sacramento Bee, in her excellent profile of chemical ecologist Walter Leal, published today on the American Association for the Advancement of Science website.
Leal, professor of entomology at the University of California, Davis, "tries to understand at the molecular level exactly what an insect is smelling, and how it relies on scent to interact with the world," she wrote.
Her article included a great quote from Leal's colleague, John Hildebrand, a neurobiology professor at the University of Arizona, Tucson.
“He’s one of the most dynamic people in the field. He’s a remarkably energetic and passionate person about his work … and notorious almost for the rapid fire way he speaks. He loves to joke that he can say twice as much in a lecture as anyone else because he only says half of each word.”
It was the Leal lab that discovered the secret mode of DEET. The groundbreaking research proved that “DEET doesn’t mask the smell of the host or jam the insect’s senses," Leal said in a UC Davis Department of Entomology news story. "Mosquitoes don’t like it because it smells bad to them.”
DEET’s mode of action or how it works puzzled scientists for more than 50 years. The chemical insect repellent, developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, is considered the "gold standard" of insect repellents worldwide. Worldwide, more than 200 million use DEET to ward off vectorborne diseases.
Scientists long surmised, incorrectly, that DEET masks the smell of the host, or jams or corrupts the insect’s senses, interfering with its ability to locate a host. Mosquitoes and other blood-feeding insects find their hosts by body heat, skin odors, carbon dioxide (breath), or visual stimuli. Females need a blood meal to develop their eggs.
In her article, Peyton Dahlberg said Leal is trying to find something better than DEET.
Wrote Peyton Dahlberg: "DEET is a flawed tool, a chemical that needs to be used at high doses, can affect human biology, and isn’t recommended for very young infants, according to Leal and others who have studied it. The point is finding something better than DEET, something more targeted to the most problematic insects and less dangerous for everything else, including people."
Leal told her that that to search for safer alternatives to DEET and other insecticides, researchers need to better understand the mechanisms of scent detection and chemical communication.
Leal indeed has a "nose for insects' sense of smell," as the AAAS headline pointed out.
The female silkworm moth releases a sex pheromone, bombykol, that's very enticing to the male. He can detect it from miles away.
Now researchers in the UC Davis Department of Entomology have discovered that the fruit fly has a native odorant receptor that detects the silkworm moth’s sex pheromone, and that it’s “amazingly more sensitive” than the moth’s odorant receptor.
Their work could open research doors for insect-inspired biosensors.Proceedings of the National Academy of Science (PNAS).
Their research follows on the heels of another study they published in PNAS in 2006 with the Deborah Kimbrell genetics lab in the UC Davis College of Biological Sciences. Bottom line: they found that genetically engineered fruit flies responded to the silkworm moth scent of a female.
Now Leal and Syed have identified the odorant receptor in the male fruit fly that detects the sex pheromone.Ecologist and evolutionary biologist Fred Gould of North Carolina State University, not affiliated with the research, says the work of the UC Davis researchers "provides important guidance and tools for other researchers who want to explore the pheromone communication systems of other species, or who want to further dissect the mechanisms within the specialized hairs of silkworms that enable this high sensitivity.”
What we have here with the silkworm moths and fruit flies is definitely not a "failure to communicate."
Scent of a Female