- Author: Kathy Keatley Garvey
(Editor's Note: This breaking news story (Oct. 27) has three connections to the UC Davis Department of Entomology and Nematology. The research began in the department; faculty member Anthony Cornel provided the mosquitoes for this research; and the father of research team member postdoctoral scholar Young-Moo completed two sabbaticals in the lab of nematologist Harry Kaya, emeritus professor, UC Davis Department of Entomology and Nematology.)
“Mosquitoes are considered the most deadly animals on the planet, but unfortunately, not everyone who needs this repellent can afford to use it, and not all who can afford it can use it due to its undesirable properties,” said Professor Leal of the Department of Molecular and Cellular Biology. One of the undesirable properties is smell.
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,” today (Oct. 27) in the Proceedings of the National Academy of Sciences (PNAS).
They examined the receptors of the southern house mosquito, Culex quinquefasciatus, which transmits such diseases as West Nile virus. Mosquitoes detect DEET and other smells with their antennae.
They discovered that the direct activation of an odorant receptor, not an ionotrophic receptor, “is necessary for DEET reception and repellency in Culex mosquitoes.” They also detected a link between DEET and methyl jasmonate, thus suggesting that DEET might work by mimicking a defensive compound from plants.
“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.”
Strickman said the paper makes “a convincing case” that the principal repellent active ingredients activate a particular odorant receptor in mosquitoes.
The same receptor, Strickman noted, is activated by a naturally occurring plant defensive compound, “suggesting that synthetic repellents take advantage of the same mechanisms that plants have developed as a result of selection exerted by herbivorous insects.”
Strickman called the research “a fascinating biological story, but it also opens the door to systematic development of highly effective repellents that would create a big improvement in personal protection. In theory, a compound that was 100,000 times more effective than current repellents might be used at much lower concentration and create completely new ways to prevent mosquito bites.”
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.
Mosquito researcher Anthony Cornel, associate professor with the UC Davis Department of Entomology and Nematology, and based at the Kearney Agricultural Research and Extension Center, Parlier, provided mosquitoes that allowed the Leal lab to duplicate his mosquito colony at UC Davis. Richard Benton of the University of Lausanne, Switzerland shared his flies, Drosophila plasmids, also part of the research. (See related story on Anthony Cornel)
The work was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.
The Leal lab published groundbreaking research in 2008 in PNAS that found that mosquitoes avoid DEET because mosquitoes dislike the smell, not because it masks the smell of the host or jams the senses. “Mosquitoes don't like it because it smells bad to them,” Leal said at the time.
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.
Related Links:
Procedings of the National Academy of Sciences (PDF)
Anthony Cornel: Mosquito Man
Close Connections (Like Father, Like Son)
News Media Contacts:
Walter Leal
Professor, Department of Molecular and Cellular Biology
Email: wsleal@ucdavis.edu
Phone: 530-752-7755
Website: http://chemecol.ucdavis.edu\
Pat Bailey
Science/agricultural writer
UC Davis News and Media Relations
Office Phone: (530) 752-9843
Cell phone: (530) 219-9640
Email: Pjbailey@ucdavis.edu
- Author: Kathy Keatley Garvey
Professor Ho Yul Choo of Gyeongsang National University, Jinju, South Korea, completed two sabbaticals in the UC Davis lab of Professor Harry Kaya and now Choo's son, Young-Moo, is a postdoctoral scholar in the UC Davis lab of chemical ecologist Walter Leal.
Young-Moo Choo, one of the authors of the ground-breaking DEET research published by the Leal lab in the Oct. 27 edition of the Proceedings of the National Academy of Sciences, maintains close family ties with nematologist Harry Kaya, emeritus professor, UC Davis Department of Entomology and Nematology.
As a visiting scientist, "Dr. Ho Yul Choo did two sabbaticals in my lab; the first was with his family in 1984-85 and Young-Moo attended elementary school in Davis," Kaya said. “Dr. Ho Yul Choo visited my lab a number of times and I visited his lab in Jinju a few times."
Young-Moo and his wife Hyang-A Won, an elementary teacher, have resided in Davis since Sept. 2, 2011.
Young-Moo received his doctorate at Dong-A University, Busan, South Korea, under professor Byung-Rae Jin. Young-Moo's younger brother, Young-Min Choo, is also a scientist who holds a doctorate. Young-Min will work as a postdoc in marine engineering at UC San Diego beginning in January 2005.
Leal first met Kaya in 1966. Kaya, who joined the UC Davis Department of Nematology (now the UC Davis Department of Entomology and Nematology), in 1976, chaired the department from 1994-2001.
Both Leal and Kaya are fellows of the Entomological Society of America (ESA). Kaya was honored at a special ESA seminar in 2011, and one of the speakers was Hol Yul Choo.
The Leal lab's groundbreaking research, “Mosquito Odorant Receptor for DEET and Methyl Jasmonate” is the work of project scientist Pingxi Xu, postdoctoral scholar Young-Moo Choo, and agricultural and environmental chemistry graduate student Alyssa De La Rosa and Professor Leal. Scientists have long known that DEET, the gold standard of insect repellents for more than six decades, effectively repels mosquitoes, but now researchers in the Leal lab have discovered the exact odorant receptor that repels them. They have also identified a plant defensive compound that might mimic DEET, a discovery that could pave the way for better and more affordable insect repellents.
Related Links:
Proceedings of the National Academy of Sciences (research paper, PDF)
Leal Lab's Groundbreaking Research (news story)
Anthony Cornel: Mosquito Man
- Author: Kathy Keatley Garvey
The yellow fever mosquito, Aedes aegypti, a newly invasive species in central California? Check.
The West Nile virus mosquito, Culex quinquefasciatus, found throughout much of the world? Check.
The malaria mosquito, Anopheles gambiae, which wreaks worldwide havoc? Check.
Cornel's name appeared in the news this week when the UC Davis lab of Walter Leal announced that it had found the odorant receptor that repels DEET in the southern house mosquito, Culex quinquefasciatus mosquito. Cornel provided the mosquitoes that allowed the Leal lab to duplicate his colony. Proceedings of the National Academy of Sciences (PNAS) published the work Oct. 27.
Cornel's main research keys in on the population genetics and ecology of West Nile virus vectors in the United States and population genetics and ecology of major malaria vectors in Africa.
“Anton is a great asset to our program, a wonderful colleague, and a nice team player,” said Leal, a professor in the Department of Molecular and Cellular Biology. “We benefit greatly from his generosity by sharing not only mosquito colonies, but also his encyclopedic knowledge on mosquito biology and ecology. We shared co-authorship in a number of publications, and many more are coming.”
Cornel collaborates with Leal on oviposition attraction in Culex quinquefasciatus and “we are now endeavoring to come up with effective oviposition attractive chemical lures to use in virus surveillance and kill traps.”
“The invasion of Aedes aegypti into central California has been of great concern especially as current control methods do not appear to be working very well,” said Cornel, who works closely with state's mosquito abatement personnel. “We have found that the Aedes aegypti have insecticide resistance genes which likely explains why their ultra-low volume (ULV) and barrier spray applications have not worked as well as expected. Work will be ongoing next year when the Aedes aegypti become active again after a brief slow overwintering period from November to March.”
A native of South Africa, Cornel received his doctorate in entomology, focusing on mosquito systematics, in 1993 from the University of the Witwatersrand, Johannesburg. He completed a post-doctoral fellowship with the Entomology Branch of the Centers for Disease Control and Prevention, Atlanta, before joining UC Davis in 1997 as an assistant professor and researcher.
“Who would have thought that that the expertise that I gained on West Nile virus as a master student in South Africa would be used many years later after West Nile virus invaded and spread throughout the USA?”
For more than two decades, Cornel has teamed with fellow medical entomologist and “blood brother” Professor Gregory Lanzaro of the UC Davis School of Veterinary Medicine to study malaria mosquitoes in the West African country of Mali. Their work is starting to show significant results.
“Because of our commitment to conduct long term longitudinal studies and not static investigations,” Cornel said, “we have now shown that considerable selective processes are taking place causing spatiotemporal dynamics of gene flow and fitness events in major malaria vectors M (now Anopheles coluzzii) and S (now Anopheles gambiae) and M/S hybrids in West Africa.” Their work was published in PNAS in 2013 (vol:110:49).
“We are currently establishing further evidence of the important role of insecticide resistance traits in spatiotemporal dynamics of Anopheles coluzzii, Anopheles gambiae and the Bamako form.” Cornel noted that these results have “considerably important implications in future efficacies of insecticide treated bednets to control indoor biting malaria vectors in West Africa.”
Cornel also teams with Lanzaro and Professor Heather Ferguson of the University of Glasgow to examine the ecology and associated genetics of the major malaria vector Anopheles arabiensis in Tanzania. They began working on the project four years ago.
“We are looking at the effects of bednet use and changes in feeding patterns of this mosquito taking population structure into consideration,” Cornel said. He and his colleagues published a paper in November 2013 in G3: Genes, Genome and Genetics, titled “Diversity, Differentiation, and Linkage Disequilibrium: Prospects for Association Mapping in the Malaria Vector Anopheles arabiensis."
One of his newest projects is the study of population/genetics, insecticide resistance and cytogenetics in the major malaria vector in Brazil. Cornel and Lanzaro launched their study in September when they traveled to Brazil to begin targeting the culprit, Anopheles darlingi, a “widely distributed species that has adapted to survive in multiple ecological zones and we suspect that it may consist of multiple incipient or closely related species,” Cornel said.
“While in Brazil I collected larvae and dissected salivary glands from them to examine their polytene chromosome inversion structure and polymorphisms,” Cornel related. “Inversions are vitally important to consider in genetic analyses and it takes considerable patience to interpret the chromosomes.”
Cornel and Lanzaro collaborate with Professor Paulo Pimenta of the Laboratory of Medical Entomology, René Rachou Research Centre- FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil. The UC Davis medical entomologists hope to produce good preliminary data from their research trip to write grants and establish a long-term project in Brazil.
Cornel also studies avian malaria. That interest sparked four years ago when he began working in Cameroon with scientists from UCLA and San Francisco State University (SFSU), including SFSU's Ravinger Sehgal, who studies avian blood parasites. Cornel's graduate student Jenny Carlson, in her final year of her Ph.D studies, is investigating avian malaria in Fresno County.
The Cornel-Carlson research implicates that considerable fidelity exists between Culex mosquito species and species of plasmodium they transmit. “This is contrary to the currently held belief that all Culex mosquitoes are equally capable of transmitting avian malaria,” Cornel said. “In our investigations, we described a new species of avian malaria which is very common in songbirds in Fresno County (published in Parasitology Research).”
Cornel plans to continue working with Sehgal investigating the effects of deforestation on transmission of avian parasites in Cameroon. They recently submitted a National Science Foundation grant proposal. “A large swath of primary forest is slated to be deforested in Cameroon and replaced with Palm oil plantations and we will investigate the effects of this hopefully, as it happens.”
Cornel will be starting a new mosquito-borne virus project in February. He received a Carnegie Foundation scholarly three-month fellowship to work in South Africa (February through to April). The primary objective of the project? To examine mosquito-borne viruses cycling in seven national parks in South Africa and two National Parks in Bostwana.
“It's extremely difficult to get permission to conduct field research in national parks in Southern Africa and this provides an unprecedented exciting opportunity for me to work with a friend, Professor Leo Braack from the University of Pretoria, in these parks. One has to be very careful working in some of these parks at night because of the wild predators, elephants, hippos and buffalo.”
Cornel is active in the 30- member Center for Vectorborne Diseases (CVEC), headquartered in the UC Davis School of Veterinary Medicine and considered the most comprehensive vectorborne disease program in California. Both interdisciplinary and global, CVEC encompasses biological, medical, veterinary and social sciences. Globally, the major emphasis is on research and education involving diseases such as malaria, dengue and leishmaniasis in the developing world. CVEC members study molecular biology, virology, parasitology, vector control, and epidemiology of vectorborne diseases. In addition, the center serves as the principal teaching resource for undergraduate and graduate courses in all facets of vector-borne disease sciences.
Related Links:
Proceedings of the National Academy of Sciences (research paper, PDF)
Research from Walter Leal Lab on DEET
Close Connections (Like Father, Like Son)
- Author: Kathy Keatley Garvey
His seminar, from 12:10 to 1 p.m., will be hosted by Michael Parrella, professor and chair of the Department of Entomology and Nematology. The seminar will be recorded for later viewing on UCTV.
"Sustainable agriculture is proving to be a challenge for many growers," Ohmart said. "They are unsure of the definition of sustainable agriculture, how to integrate the concept into their farm management, and how to measure its value to their production bottom line. SureHarvest has developed a framework that growers, grower groups and companies can use to design, implement and measure sustainability performance. The framework is called SureHarvest's 5 Ps of sustainability. The model evolved out of SureHarvest's work with the California wine industry since 2002 and is designed to meet those challenges."
Ohlmart will discuss the evolution of the framework and the tools that have been developed to facilitate program implementation. "This includes an online program management software platform that contains an online self-assessment workbook of sustainable farming practices, a reporting system for instant feedback on a grower's self-assessment and educational content in context on sustainable farming practices."
SureHarvest has also been working with the Almond Board of California designing and implementing the California Sustainable Almond Program and with the California Cut Flower Commission developing a program for the sustainable production of cut flowers, said Ohmart, who also will discuss these programs. He will zero in on "lessons learned about the challenges of getting grower engagement in sustainability programs, including the role of the University of California research and extension."
Ohmart received his bachelor's degree in forest biology from the College of Environmental Science and Forestry, State University of New York (SUNY) and his Ph.D. in entomology from UC Berkeley. He was a principal research scientist for Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Forest Research in Australia for 13 years where he did basic research on insect pests of Monterey pine and Eucalyptus.
His biography also includes:
- From 1989 to 1995 he worked as a private consultant for Scientific Methods, Inc. in Chico, Calif., helping growers develop and implement integrated pest management (IPM) programs for almonds, apples, walnuts, prunes, and pistachios.
- From 1996 to 2009 he was the Sustainable Winegrowing director for the Lodi Winegrape Commission where he helped them develop what has become an internationally recognized sustainable winegrowing program. This included creating the Lodi-Winegrower's Workbook program and the Lodi Rules for Sustainable Winegrowing program, California's first third party-certified sustainable winegrowing program.
- Since late 2009, he has served as vice president of professional services with SureHarvest, a company that provides a complete set of sustainability solutions for growers, grower groups, and Agrifood companies. He has presented more than 300 seminars, conference papers and symposia papers at universities, government research organizations, and grower groups throughout the United States, Canada, Australia, New Zealand, Sweden and Finland and is very active at the county, state and national level in pest management and agriculture industry affairs.
In addition, Ohlmart serves on the boards of Protected Harvest, the Association of Applied IPM Ecologists, and the Advisory Board of the Cal Poly Center for Sustainability. He recently published the book View from the Vineyard: A Practical Guide to Sustainable Winegrape Growing.
His seminar will be recorded for later posting on UCTV.
Upcoming seminars:
Wednesday, Nov. 5
Chuck Fox
Professor, University of Kentucky, specializing in ecology and evolution of life histories; insect-plant interactions; insect behavioral ecology
Title: "Inbreeding-Environment Interactions: Experimental Studies and a Meta Analysis"
Host: Jay Rosenheim, professor, Department of Entomology and Nematology
Wednesday, Nov. 12
Louie Yang
Assistant professor, UC Davis Department of Entomology and Nematology, specializing in ecology
Title: "Pulses, Phenology and Ontogeny: Towards a More Temporally Explicit Framework for Understanding Species Interactions?"
Wednesday, Nov. 19
Ray Hong
Associate professor of biology, California State University, Northridge, specializing in nematology
Title: “A Fatal Attraction: Regulation of Development and Behavior in the Nematode Pristionchus pacificus by a Beetle Pheromone”
Host: Valerie Williamson, professor of nematology, Department of Entomology and Nematology
Wednesday, Nov. 26
Doris Bachtrog, lab
Associate professor of integrative biology, UC Berkeley, specializing in evolutionary and functional genomics
Title: "Numerous Transitions of Sex Chromosomes in Diptera"
Host: Michael Parrella, professor and chair, Department of Entomology and Nematology
Wednesday, Dec. 3
To be announced
Wednesday, Dec. 10
Sawyer Fuller
Postdoctoral researcher, Harvard University
Title: "RoboBee: Using the Engineering Toolbox to Understand the Flight Apparatus of Flying Insects"
Host: James Carey, distinguished professor of entomology
This seminar is being remote broadcast to UC Davis via internet
Contacts:
Steve Nadler, sanadler@ucdavis.edu
Professor, UC Davis Department of Entomology and Nematology
Jesael "Jesa" David, jcdavid@ucdavis.edu
Student Affairs Officer, Graduate Programs
Plant Pathology, Entomology and Nematology
- Author: Kathy Keatley Garvey
Of the 20,000 bee species identified worldwide, some 4000 are found in the United States, and 1600 in California.
The book, the first of its kind, profiles some of the most common bee genera found in California gardens; their preferred plants, both native and non-native; and how to attract them.
In addition to the well-known honey bees and bumble bees, the authors spotlight such bees as mining, leafcutting, carpenter, sweat, digger, masked, longhorned, mason and polyester bees.
The honey bee, which provides pollination services valued at $217 billion globally and $20 million in the United States alone, is the most recognizable of the bees, but many are unaware of its non-native status. European colonists brought the honey bee to America in 1622.
California Bees and Bloom, published by the nonprofit Heyday Books in collaboration with the California Native Plant Society, is the work of urban entomologist Gordon Frankie. a professor and research entomologist at UC Berkeley; native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis; insect photographer and entomologist Rollin Coville, who holds a doctorate in entomology from UC Berkeley; and botanist/curator Barbara Ertter of UC Berkeley.
“This book is about urban California's bees: what they are, how and where they live, their relationships with ornamental flowers, and how to attract them to urban gardens,” they wrote. “It was written in the urgency of knowing that bees are critical to the health of our natural, ornamental and agricultural landscapes and that populations of some, perhaps many are in rapid decline.”
“While the book is specific to California, larger insights can be gathered about the role of native bees in developed landscapes (such as agriculture), and native bee conservation,” said Frankie, who researched bees in urban gardens in California for 13 years.
The book traces the first fossilized bee to Burma's Hukawng Valley, where it was lodged in amber approximately 100 million years ago.
The book destroys such myths as:
1. All bees make honey. Fact: Most native bees make no honey at all.
2. Bees die after they sting. Fact: Only the honey bees die; native solitary bees do not.
3. Male bees don't pollinator flowers. Fact: Male engage in pollination, but are not as efficient as most females.
4. Honey bees displace native bees on flowers. Fact: There is no evidence of that. In fact, “Recent research does indicate that interaction between honey bees and native bees results in an increase in the activity and efficiency of honey bees with regard to visiting (and pollinating) crops.”
California's bees differ in size, shape and color, as do the flowers they visit. “The tiniest bees are ant-sized; the largest rival small birds,” they wrote. “Some are iridescent green or blue, some are decked out with bright stripes, some are covered with fuzzy-looking hairs.”
Co-author Gordon Frankie's specialty is behavioral ecology of solitary bees in wildland, agricultural and urban environments of California and Costa Rica. He teaches conservation and environmental issues. He is involved in how people relate to bees and their plants and how to raise human awareness about bee-plant relationships.
Co-author Robbin Thorp, who retired in 1994 after 30 years of teaching, research and mentoring graduate students, continues to conduct research on pollination biology and ecology, systematics, biodiversity and conservation of bees, especially bumble bees. He is one of the instructors at the The Bee Course, affiliated with the American Museum of Natural History and held annually at the Southwestern Research Station, Portal, Ariz. The course is geared for conservation biologists, pollination ecologists and other biologists who seek greater knowledge of the systematics and biology of bees.
“The book is profusely illustrated with photos and drawings of bees and flowers, especially notable are the magnificent close up images of bees by co-author Rollin Coville,” Thorp said.
California Bees and Blooms lists 53 of urban California's best bee attractors identified through the Urban California Native Bee Survey. Among them: aster, bluebeard, catmint, California lilac or Ceanothus, cosmos, California sunflower, red buckwheat, California poppy, blanket flower, oregano, rosemary, lavender, gum plant, and salvia (sage). With each plant, they provide a description; origin and natural habitat, range and use in California; flowering season; resource for bees (such as pollen and nectar), most frequent bee visitors, bee ecology and behavior and gardening tips.
The book offers tips on how readers can “think like a bee.” It devotes one chapter to “Beyond Bee Gardening: Taking Action on Behalf of Native Bees.” In addition, the book provides quotes on bees and/or bee gardens from Extension apiculturist Eric Mussen (retired) of UC Davis: Ellen Zagory, horticulture director of the UC Davis Arboretum; and Kate Frey of Hopland, a designer of sustainable, insect-friendly gardens throughout California and in some parts of the world.
For more data on the book, the authors, and purchase information, access the publisher's website at https://heydaybooks.com/book/california-bees-and-blooms/
For ongoing research on California's bees and blooms, see the UC Berkeley website, www.helpabee.org.