Posts Tagged: Walter Leal
However, not everyone wants to use DEET, a synthetic insect repellent. There's that smell, for one thing. "Properties that people do not like in addition to the smell is that DEET is a solvent for plastic," says chemical ecoloigst Walter Leal of the University of California, Davis. "So, one gets eyeglass frames and watchbands dissolved by DEET."
There's also "the misconception that everything synthetic is bad."
So what is it with DEET that repels mosquitoes? What odorant receptor is involved? Mosquitoes, as we know, detect smells with their antennae.
The Leal lab today (Oct. 27) published research in the Proceedings of the National Academy of Sciences (PNAS) that pinpoints the exact odorant receptor that repels them. They also identified a plant defensive compound that might mimic DEET, a discovery that could pave the way for better and more affordable insect repellents.
For more than six decades, DEET has been known as the gold standard of insect repellents. More than 200 million people worldwide use the chemical insect repellent, developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946.
So when Leal and his team--project scientist Pingxi Xu, postdoctoral scholar Young-Moo Choo, and agricultural and environmental chemistry graduate student Alyssa De La Rosa-- published their groundbreaking research, “Mosquito Odorant Receptor for DEET and Methyl Jasmonate,” they drew global attention.
In their research, they examined the receptors of the southern house mosquito, Culex quinquefasciatus, which transmits such diseases as West Nile virus.
The researchers set out to investigate two hypotheses regarding DEET's mode of action: activation of ionotropic receptor IR40a vs. odorant receptor(s). “Ionotropic receptor is another family of olfactory receptors, which seem to be the ancestral version when insects were aquatic,” Leal said. “So, the ionotropic receptors normally detect acid, bases, and other water soluble compounds.”
“Vector-borne diseases are major health problems for travelers and populations living in endemic regions,” said Leal. “Among the most notorious vectors are mosquitoes that unwittingly transmit the protozoan parasites causing malaria and viruses that cause infections, such as dengue, yellow fever, chikungunya, and encephalitis.”
Leal said that diseases transmitted by mosquitoes destroy more lives annually “than war, terrorism, gun violence, and other human maladies combined. Every year, malaria decimates countless lives – imagine a city of San Francisco perishing to malaria year after year. The suffering and economic consequences in endemic areas are beyond imagination for those living in malaria-free countries. Both natives and visitors to endemic areas want to keep these ‘infected needles' at bay. In the absence of vaccines for malaria, dengue, and encephalitis, one of the most ancient and effective prophylactic measures against mosquito-borne diseases is the use of DEET.”
Dan Strickman of the Bill and Melinda Gates Foundation, not involved in the study, praised the work. “We are at a very exciting time for research on insect repellents,” said Strickman, senior program officer of the Global Health Program's Vector Control. “ For decades, the field concentrated on screening compounds for activity, with little or no understanding of how chemicals interacted with mosquitoes to discourage biting. Use of modern techniques that combine molecular biology, biochemistry, and physiology has generated evidence on how mosquitoes perceive odors.”
Said zoologist Paul Weldon of the Smithsonian's Conservation Biologist Institute, also not involved in the study: “Since DEET is strictly synthetic and not a natural product, it has been challenging to understand the adaptive nature of the response it elicits. It is not as if the compound emanates from, say, spider webs or fishy water, where avoidance by mosquitoes would make sense. Xu et al. have solved the mystery of where the DEET response comes from: it is in response to plant chemical defenses.”
“This, by the way, also explains why the DEET response is widespread, occurring in many arthropods, including those that are not ectoparasitic -- like cockroaches,” Weldon said. The repellence of other arthropods by DEET may have tipped off some of those investigating the DEET response, but I'm not sure that it did. The focus of research on DEET seems to have been with the organisms in which it just so happened to be discovered -- mosquitoes. The Xu et al. study suggests that there is a much broader array of DEET-sensitive organisms than previously suspected. No doubt, this finding will assist further investigations of it.”
Professor John Pickett, Rothamsted Research, UK, also not involved in the study, called the link between the plant compound and synthetic insect repellent, DEET as a “surprising evolutionary link.”
Pickett, the Michael Elliott Distinguished Research Fellow and Scientific Leader of Chemical Ecology at Rothamsted Research and a foreign associate of the National Academy of Sciences, said: “Not only does this work demonstrate that a mosquito response to the gold standard repellent DEET, as well as the more recently developed repellents, is mediated by a specific odorant receptor (OR136 for the southern house mosquito Culex quinquefasciatus) but that the receptor responds specifically also to methyl jasmonate, involved in plant hormone-based defense against insects, which suggests a surprising evolutionary link between these types of insect interactions.”
The UC Davis researchers pointed out that “insect repellents have been used since ancient times as prophylactic agents against diseases transmitted by mosquitoes and other arthropods, including malaria, dengue fever, and encephalitis. They were developed from plant-based smoke or extracts (essential oils) into formulations with a single active ingredient.”
Progress toward development of better and more affordable repellents has been slow, they said, because scientists weren't sure which odorant receptor was involved. Now they are.
Mosquito researcher Anthony "Anton" Cornel, associate professor with the UC Davis Department of Entomology and Nematology, and based at the UC Kearney Agricultural Research and Extension Center, Parlier, provided the mosquitoes that allowed the Leal lab to duplicate his mosquito colony at UC Davis.
Look for more exciting research to come!
UC Davis scientists in the Walter Leal lab have discovered the odorant receptor in the Culex mosquito that repels DEET. From left are project scientist Pingxi Xu; postdoctoral scholar Young-Moo Choo; AgChem graduate student Alyssa De La Rosa; and Professor Leal. (Photo credit: Academic Technology Services/Mediaworks)
When chemical ecologist Walter Leal, professor of entomology at the University of California, Davis, was elected to the prestigious Brazilian Academy of Sciences, his lab members donned matching t-shirts--t-shirts with a touch of humor and a dose of humility.
On the front: "I did the work."
On the back: "And Walter Leal got in the Academy."
It was his idea and he purchased the t-shirts.
Leal, a native of Brazil, will be honored at a ceremony on May 7 in Rio de Janeiro.
“Let me say that your election to the Brazilian Academy of Sciences is a well-deserved recognition for your accomplishments as a distinguished scientist in your field of studies, entomology, and also for the very important role you have been playing in promoting cooperation among Brazilian and U.S .universities and, through those arrangements, fostering scientific development in our country,” said Ambassador Eduardo Prisco of the Brazilian Consulate in San Francisco.
Leal, a native of Brazil, is a liaison with UC Davis and the Brazil government’s Scientific Mobility Program, launched to exchange graduate and undergraduate students.
The U.S. currently hosts the largest number of students participating in the Brazil government’s Scientific Mobility Program, according to the Institute of International Education, and UC Davis leads the nation, hosting more than 30 Brazilian undergraduate scholarship students. Leal is also involved in the Brazilian/UC Davis student exchange with the Federal Agency for Support and Evaluation of Graduate Education (CAPES) and the National Council for Scientific and Technological Development (CNPq) grants for research related to Brazil.
A pioneer in the field of insect communication and on the cutting edge of research, Leal employs innovative approaches to insect olfaction problems. His work examines how insects detect smells, communicate with their species, detect host and non-host plants, and detect prey. Leal has designed and synthesized complex pheromones from many insects, including scarab beetles, true bugs, longhorn beetles and the citrus leafminer. He and his lab discovered the secret mode of the insect repellent DEET.
Leal, educated in Brazil and Japan, joined the UC Davis Department of Entomology in 2000. He holds a doctorate in applied biochemistry from Tsukuba University, Japan, and also earned degrees in chemical engineering and agricultural chemistry.
You'll be hearing much more of Walter Leal. Active in national and international entomological circles, the UC Davis professor is serving as co-chair of the International Congress of Entomology (ICE) conference, to be hosted by the Entomological Society of America (ESA) Sept. 25-30, 2016 in Orlando, Florida.
His honors and awards are many. He is a Fellow of the ESA, the Royal Entomological Society, and the American Association for the Advancement of Science. He served as president of the International Society of Chemical Ecology (ISCE). Among his awards: the ISCE Silver Medal, and awards from ESA and scientific societies in Japan and Brazil.
Caption (Top Photo):
The Walter Leal lab wore humorous t-shirts to announce his selection to the Brazilian Academy of Sciences. Four countries are represented in this lab photo. The four in front are (from left) Junior Specialist Hang Gao, United States; Professor Fen Zhu, Huazhong Agricultural University, China; Professor Leal, a native of Brazil; and Graduate Student Alyssa De La Rosa (Agricultural and Environmental Chemistry Graduate Group). Circling them in back are (from left) Postdoctoral Fellow Cherre Sade, Brazil; Postdoctoral Fellow Young-Moo Choo, Korea; Project Scientist Pingxi Xu, China; Graduate Student Kevin Cloonan (entomology major), Professor Carlos Ueira Vieira, Federal University of Uberlandia, Brazil; Graduate Student Yinliang Wang, Northeast Normal University, China; and Graduate Student Washington Carvalho, Federal University of Uberlandia.
The Walter Leal lab wearing matching t-shirts. See caption at end of the blog. (Photo by Kathy Keatley Garvey)
Walter Leal (back to camera) talking to his lab members. (Photo by Kathy Keatley Garvey)
UC Davis entomology graduate student Kevin Rayne Cloonan not only won a coveted award for his research presentation at the 60th meeting of the Entomological Society of America in Knoxville, Tenn., but it may prove to be a boon to California almond growers.
Cloonan, who is studying for his master’s degree with chemical ecologist Walter Leal, professor of entomology, won a second-place award for his insect repellent research on the navel orangeworm (NOW), a major pest of California’s almond industry.
His talk was part of the 10-minute graduate student presentations.
Cloonan presented his paper on “Potential Oviposition Repellent for the Navel Orangeworm (Amyelois transitella) in Almond Orchards of Central California.” For his research, he tested 20 broad spectrum insect repellents as potential oviposition repellents. Bedoukian Research Inc. developed the repellents.
Cloonan's work involved electrophysiological recordings, laboratory behavioral assays, and a field behavioral assay. He first used electroantennogram (EAG) assays to identify which of those 20 repellents the female antennae could detect. Of the 20 repellents, three showed significant EAG responses, he said.
In testing the oviposition repellency under laboratory conditions with laboratory populations, he found that two of the three repellents showed significantly reduced oviposition; they were then tested with field populations in almond orchards in Arbuckle.
“One especially looks very promising,” said Cloonan, adding “I couldn’t have done this research without the support and help of Dr. Leal and everyone in the Leal lab.”
Cloonan has been asked to present a poster at the Almond Board of California conference, to be held Dec. 11-13 at the Sacramento Convention Center.
At the ESA meeting, Cloonan’s presentation was one of 14 vying for top honors in the Plant-Insect Ecosytems (P-IE) Section. The P-IE Section includes behavioral, ecological, and evolutionary relationships in natural landscapes, as well as integrated pest management (IPM) in agriculture, horticulture, forests, and lawn and garden. The section also deals with aspects of crop protection, host-plant response, plant pathology/vectors, pollination, biological control, microbial control, and others.
Cloonan, who plans to pursue his doctorate in entomology, is a graduate of the University of Idaho, with a bachelor's degree in entomology.
Almonds are big business in California and getting bigger.
The National Agricultural Statistics Service forecasts California’s 2012 almond crop at a record-breaking 2.10 billion meat pounds, valued at approximately $3 billion. Eighty-percent of the global supply of almonds is grown in California, and about 70 percent of California’s crop is marketed overseas.
Honey bees from all over the country are trucked to California to pollinate the state’s 780,000 acres of almonds, which begin blooming in mid-February, around Valentine's Day. Two bee colonies are required to pollinate each acre--and that's a lot of bees!
Navel orangeworms lay their eggs in almonds, pistachios and walnuts, with the resulting caterpillars (larvae) causing major damage. This is an adult on a pistachio. (Photo by Kathy Keatley Garvey)
Walter Leal isn’t participating in the Olympics, but he medaled just the same.
It was not for athletic prowess, but for scholarly achievements—the scientific equivalent of an international gold medal.
Leal, a chemical ecologist and a professor and former chair of the UC Davis Department of Entomology, is the recipient of the coveted Silver Medal, the highest award given by the International Society of Chemical Ecology (ISCE).
A native of Brazil and educated in Brazil and Japan, Leal researches how insects detect smells and communicate within their species. He is “one of the foremost authorities on the integration of chemical ecology with the molecular, biochemical and physiological interactions among insects and between insects and plants,” said chemical ecologist Coby Schal, professor at North Carolina State University, who nominated him for the award.
Bruce Hammock, UC Davis distinguished professor of entomology, wrote a letter of support, praising Leal for “his outstanding career achievements and excellence in moving chemical ecology forward." Hammock described him as “a world-renowned chemical ecologist, a pioneer in the field of insect olfaction, and on the cutting edge of research.”
ICSE president Paulo H. G. Zarvin of the Federal University of Parana, Brazil announced the award July 26 at the 28th annual ISCE annual meeting, held in Lithuania. It will be presented at the ISCE’s 29th annual meeting, set Aug. 19-22, 2013 in Melbourne, Australia.
Declaring Leal’s program, launched in 1990, as “one of the best in the world,” Schal lauded Leal as “one of the most energetic and collaborative scientists I know.”
“Chemical signaling is fundamental to all life forms, including microbes, plants and animals,” Schal said,” and chemical cues allow animals to appraise their environment; to detect food, toxins, prey, predators and pathogens; to identify kin; and to evaluate and base mate choice decisions of potential reproductive partners.”
“Walter’s research, in two decades, has addressed almost every aspect of chemical ecology,” Schal said. That includes “the semiochemistry of mites, thrips, scarabs, bugs, aphids, cockroaches, moths, wasps and plants.”
Leal, who joined the UC Davis faculty in 2000, has designed and synthesized complex pheromones from many insects, including scarab beetles, true bugs, longhorn beetles and the citrus leafminer. He identified the complex sex pheromone system of the naval orangeworm, a key agricultural pest responsible for multi-million crop damage annually in California. The sex pheromones he discovered are now being deployed in the agricultural field to disrupt chemical communication and control the navel orangeworm population through the environmentally friendly technique of mating disruption.
Leal and his lab discovered DEET’s mode of action, something that had puzzled and eluded scientists for half a century. Scientists long surmised that DEET, patented by the U.S. Army in 1946, works by masking the smell of the host, or jamming the insect’s senses, thus interfering with its ability to locate a host. Not so: in groundbreaking research published in the Proceedings of the National Academy of Sciences (PNAS), the Leal lab found that mosquitoes can indeed smell the chemical repellent but they dislike it so they avoid it.
Leal is one of only 23 scientists to receive the ISCE Silver Medal since its inception in 1986. Two other University of California scientists also won the award: Dave Wood of UC Berkeley in 2001 and Ring Cardé of UC Riverside in 2009.
Chemical ecologist Walter Leal. (Photo by Kathy Keatley Garvey)
Call it a case of royalty plus.
UC Davis chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology, has just received a double honor. He was elected a Fellow of the Royal Entomological Society and he received a coveted award from his native Brazil.
First the royalty...It's an honor just to be nominated for the Fellow award. Among the imminent scientists who've received the award: Charles Darwin.
The Royal Entomological Society, based in London, disseminates information about insects and strives to improve communication among entomologists at the national and international level. Its history is long and rich. Founded in London in 1833, it is a successor to a number of short-lived societies dating back to 1745.
The origin of the "royalty?" name? In 1885 Queen Victoria granted a Royal Charter to the society. In the centennial year of 1933, King George V added the word "Royal" to the title.
The other honor? The coveted award, the 2nd National Award of Chemical Ecology, that Leal received in Brazil is linked closely to two people who have influenced him in his academic career and everyday life.
The award memorializes his former mentor, Professor Jose Tercio Barbosa, a pioneer in the field of chemical ecology. As part of the award, Leal received a book on the Museum of Contemporary Art Niteroi signed by internationally known Brazilian architect Oscar Niemeyer.
Niemeyer, now a "young" 104 years old, designed the United Nations’ headquarters in New York City, and many public buildings in Brazil, including the Cathedral of Brasilia, the Museum of Modern Art of Caracas and the Niterói Contemporary Art Museum, Rio de Janeiro.
“I grew up hearing about the wonderful work of Oscar Niemeyer, but never even imagined that one day I would get his autograph," Leal said. "It is sad, however, that it happened in part because Professor Tercio, a pioneer in the field of chemical ecology, passed away prematurely. Earlier on, Tercio introduced me to the scientific community in Brazil."
"Niemeyer is one of the two most famous contemporary Brazilians," Leal said. "The other is Pelé whom I've known since my years of working as a radio sportscaster to help fund my college education."
The path from sportscaster to chemical ecologist was a long one. Today Leal focuses his research on how insects detect smells, communicate with their species, detect host and non-host plants, and detect prey. For his innovative approaches to insect olfaction problems, the Entomological Society of America named him the 2011 recipient of Entomological Society of America's Nan-Yao Su Award for Innovation and Creativity in Entomology.
The circle widens, then narrows, then widens again.
Chemical ecologist Walter Leal in front of a silkworm moth depiction. (Photo by Kathy Keatley Garvey)