- Walter Leal, distinguished professor, Department of Molecular and Cellular Biology and former chair of the Department of Entomology (now the Department of Entomology and Nematology
- Cristina Davis, the Warren and Leta Geidt Endowed Professor and Chair, Department of Mechanical and Aerospace Engineering
NIA honors and encourages academic inventions that benefit society. Between the two UC Davis faculty members, they hold 42 patents: Davis with 12; and Leal with 28 Japanese and 2 U.S. patents.
Davis is a world leader in trace chemical sensing, while Leal is a leading global scientist in the field of insect olfaction and communication, investigating how insects detect odors, how they detect host and nonhost plant matter, and how they communicate within their species.
Leal's research, spanning three decades, focuses on insects that carry mosquito-borne diseases as well as agricultural pests, such as the Asian citrus psyllid and the orange navelworm. He and his lab drew international attention with their discovery of the mode of action of DEET, the gold standard of insect repellents.
We remember when Leal and a group of 18 students hosted a Zika Public Awareness Symposium in 2016 on the UC Davis campus. It was an amazing symposium that drew attention to Aedes aeqytpi, which transmits the disease. Soon thereafter, Brazilian-born Leal and his colleagues in Brazil, detected the Zika virus in wild-caught Culex quinquefasciatus mosquitoes in Recife, the epicenter of the Zika epidemic.
We also remember when Leal identified the sex pheromones of the navel orangeworm (Amyelois transitella), a pest of almonds, figs, pomegranates and walnuts, the major hosts. This led to practical applications of pest management techniques in the fields.
Those are just several examples of the work he does. And still, he found time to co-chair the 2016 International Congress of Entomology meeting, "Entomology Without Borders," in Orlando, Fla., that drew the largest delegation of scientists and experts in the history of the discipline: 6682 attendees from 102 countries.
We're not sure how Leal can find the time to do all this (see news story on the UC Davis Department of Entomology and Nematology). We figure he must have a clone! Make that multiple clones!
At any rate, Leal is the second faculty member affiliated with the entomology department to be selected an NIA fellow. The other scientist: Bruce Hammock, distinguished professor, who holds a joint appointment in the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center. Hammock is the co-founder and chief executive officer of EicOsis LLC, a Davis-based company that is developing a non-opiate drug to relieve inflammatory pain in companion animals and target chronic neuropathic pain in humans and horses.
As Hammock said: “When Walter Leal reached UC Davis (in 2000), he came with the reputation of being a 'one man army in research.' This reputation was well deserved. I know of no one at UC Davis who matches Walter in taking his remarkable fundamental advances in science and translating them to increase the safety and magnitude of world food production.”
Wait, there's more! "Not So Heartless: Functional Integration of the Immune and Circulatory Systems of Mosquitoes."
This may not be the proverbial heart-stopping seminar, but it promises to be an eye opener by a medical entomologist and captivating speaker.
Julián Hillyer, associate professor of biological sciences, Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, Tenn., will deliver that seminar at 4:10 p.m., Wednesday, Oct. 23, in 122 Briggs Hall, as part of the weekly UC Davis Department of Entomology and Nematology seminars.
"Mosquitoes--like all other animals--live under constant threat of infection," Hillyer says in his abstract. "Viral, bacterial, fungal, protozoan and metazoan pathogens infect mosquitoes through breaches in their exoskeleton and following ingestion. Because these pathogens pose a threat to their survival, mosquitoes have evolved a powerful immune system."
In his seminar, Hillyer will present his laboratory's work characterizing the circulatory and immune systems of the African malaria mosquito, Anopheles gambiae. "Specifically," he says. "the talk will describe the structural mechanism of hemolymph (insect blood), circulation in different mosquito life stages, and the role that immune cells, called hemocytes play in the killing of pathogens by phagocytosis, melanization and lysis. Then I will describe the functional integration of the circulatory and immune systems a process that is manifested differently in larvae and adults. Specifically, the infection of an adult mosquito induces the aggregation of hemocytes at the abdominal ostia (valves) of the heart--where they sequester and kill pathogens in areas of high hemolymph flow--whereas the hemocytes of larvae aggregate instead on respiratory structures that flank the posterior in current openings of the heart."
"This research," Hillyer explains, "informs on the physiological interaction between two major organ systems and uncovers parallels between how the organ systems of invertebrate and vertebrate animals interact during the course of an infection."
What does the mosquito heart look like? Check out former Vanderbilt graduate student Jonas King's prize-winning image--a fluorescent image of the heart of a mosquito. It won first place in Nikon's "Small World'" photomicrography competition in 2010. King's image shows a section of the tube-like mosquito heart magnified 100 times. At the time he was a member of Hillyer's research group and is now an assistant professor at Mississippi State University.
In a piece by David Salisbury of Vanderbilt News, Hillyer related that "Surprisingly little is known about the mosquito's circulatory system despite the key role that it plays in spreading the malaria parasite. Because of the importance of this system, we expect better understanding of its biology will contribute to the development of novel pest- and disease-control strategies.”
"The mosquito's heart and circulatory system is dramatically different from that of mammals and humans," wrote Salisbury in the Oct. 15, 2010 piece. "A long tube extends from the insect's head to tail and is hung just under the cuticle shell that forms the mosquito's back. The heart makes up the rear two-thirds of the tube and consists of a series of valves within the tube and helical coils of muscle that surround the tube. These muscles cause the tube to expand and contract, producing a worm-like peristaltic pumping action. Most of the time, the heart pumps the mosquito's blood—a clear liquid called hemolymph—toward the mosquito's head, but occasionally it reverses direction. The mosquito doesn't have arteries and veins like mammals. Instead, the blood flows from the heart into the abdominal cavity and eventually cycles back through the heart."
“The mosquito's heart works something like the pump in a garden fountain,” Hillyer told Salisbury.
Hillyer was a Vanderbilt Chancellor Faculty Fellow (2016-2018) and was awarded the 2015 Henry Baldwin Ward Medal by the America Society of Parasitologists. He was elected to the Council of the American Society of Parasitologists, serving from 2012-2016. Other recent awards: the 2011 Jeffrey Nordhous Award for Excellence in Undergraduate Teaching and the 2012 Recognition Award in Insect Physiology, Biochemistry and Toxicology from the Southeastern Branch of the Entomological Society of America.
Hillyer received his master's degree and doctorate from the University of Wisconsin-Madison under the mentorship of Ralph Albrecht and Bruce Christensen, respectively. He completed a postdoctoral fellowship under the mentorship of Kenneth Vernick at the University of Minnesota, now with Institut Pasteur. In 2007, Hillyer moved to Nashville, Tenn. to establish Vanderbilt University's mosquito immunology and physiology laboratory. (See more.)
The Hillyer Lab is interested in basic aspects of mosquito immunology and physiology, focusing on the mechanical and molecular bases of hemolymph (blood) propulsion, and the immunological interaction between mosquitoes and pathogens in the hemocoel (body cavity)," according to his website. "Given that chemical and biological insecticides function in the mosquito hemocoel, and that disease-causing pathogens traverse this compartment prior to being transmitted, we expect that our research will contribute to the development of novel pest and disease control strategies."
Host is Olivia Winokur, doctoral student in the Chris Barker lab. Community ecologist Rachel Vannette, assistant professor, Department of Entomology and Nematology, coordinates the weekly seminars. (See list of seminars)
Nine speakers are booked for the fall quarter seminars sponsored by the UC Davis Department of Entomology and Nematology. The seminars begin Wednesday, Sept. 25 and continue through Wednesday, Dec. 5.
Coordinated by assistant professor and community ecologist Rachel Vannette, the seminars will take place at 4:10 p.m., every Wednesday in Room 122 of Briggs Hall except on Nov. 20 (no seminar due to the Entomological Society of America meeting in St. Louis, Mo).
James Nieh, professor, Section of Ecology, Behavior and Evolution, Department of Biological Sciences, UC San Diego
Topic: "Animal Information Warfare: How Sophisticated Communication May Arise from the Race to Find an Advantage in a Deadly Game Between Honey Bees and their Predators" (See lab website)
Host: Brian Johnson, associate professor, Department of Entomology and Nematology
Nathan Schroeder, assistant professor, Department of Crop Sciences, University of Illinois, Urbana-Champaign
Topic: "Stem Cells and Neurobiology of Nematodes"
Host: Shahid Saddique, assistant professor, Department of Entomology and Nematology
John Mola, doctoral candidate, Neal Williams lab, Graduate Group in Ecology
Exit seminar: "Bumble Bee Movement Ecology and Response to Wildfire." Mola specializes in bee biology, pollinator ecology and population genetics.
Host: Neal Williams, professor, Department of Entomology and Nematology
Rebecca Irwin, professor, applied ecology, North Carolina State University, Raleigh, N.C.
Topic: (to be announced; she specializes in the ecology and evolution of multiple-species interactions, pollination biology, and species invasions)
Host: Rachel Vannette, assistant professor, Department of Entomology and Nematology
Julián Hillyer, director of the program in career development and associate professor of biological sciences, Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, Tenn.
Topic: "Not So Heartless: Functional Integration of the Immune and Circulatory Systems of Mosquitoes"
Host: Olivia Winokur, graduate student, Chris Barker lab
Takato Imaizumi, professor, Department of Biology, University of Washington, Seattle
Topic: Circadian Timing Mechanisms in Plant-Pollinator Interaction"
Host: Joanna Chiu, associate professor and vice chair of the Department of Entomology and Nematology
Brock Harpur, assistant professor, Department of Entomology, Purdue University
Topic: "Caste Differentiation in Honey Bees from the Bottom Up"
Host: Santiago Ramirez, associate professor, UC Davis Department of Evolution and Ecology, College of Biological Sciences
Allison Hansen, assistant professor, Department of Entomology, UC Riverside
Topic: Insect Herbivore-Microbe Interactions
Host: Clare Casteeel, assistant professor, UC Davis Department of Plant Pathology
No seminar (meeting of Entomological Society of America in St. Louis, Mo.)
Jackson Audley, doctoral candidate, Louie Yang lab and Steve Seybold lab
Exit seminar (topic to be announced). Audley studies the walnut twig beetle, Pityophthorus juglandis, which in association with the fungus, Geosmithia morbida, causes the insect-pathogen complex known as thousand cankers disease.)
Host: Steve Seybold, lecturer, forest entomology, UC Davis Department of Entomology and Nematology and forest entomologist and chemical ecologist with the Pacific Southwest Research Station, USDA Forest Service, Davis
The seminars are free and open to all interested persons. Some will be recorded for later viewing on YouTube. More information on the fall seminars or schedule is available from Vannette at firstname.lastname@example.org.
They manage to find us, don't they? Even when we're doing our best to try to avoid them!
It's not so well-known that mosquitoes, both male and female, frequent plants to feed on nectar for energy.
And now UC Davis chemical ecologist Walter Leal and scientists Fangfang Zen and Pingxi Xu of the Leal lab have discovered that the odorant receptors from the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito Aedes aegypti, are sensitive to floral compounds.
The manuscript: "Odorant Receptors from Culex quinquefasciatus and Aedes aegypti Sensitive to Floral Compounds."
The team, led by Leal, a distinguished professor in the Department of Molecular and Cellular Biology and a former chair of the UC Davis Department of Entomology, cloned the genes of several odorant receptors from the mosquitoes and tested them, using egg cells of Xenopus toads. They exposed the cloned receptors to different scent chemicals.
"We are delighted to find out how mosquitoes smell plant-derived compounds and are repelled by them," Leal said. "These findings may lead to the discovery of better repellents from natural sources."
"Mosquitoes rely heavily on the olfactory system to find a host for a bloodmeal, plants for a source of energy and suitable sites for oviposition," the scientists explained in their abstract. "Here, we examined a cluster of 8 odorant receptors (ORs), which includes one OR, CquiOR1, previously identified to be sensitive to plant-derived compounds. We cloned 5 ORs from Culex quinquefasciatus and 2 ORs from Aedes aegypti, ie, CquiOR2, CquiOR4, CquiOR5, CquiOR84, CquiOR85, AaegOR14, and AaegOR15 and then deorphanized these receptors using the Xenopus oocyte recording system and a large panel of odorants. 2-Phenylethanol, phenethyl formate, and phenethyl propionate were the best ligands for CquiOR4 somewhat resembling the profile of AaegOR15, which gave the strongest responses to phenethyl propionate, phenethyl formate, and acetophenone. In contrast, the best ligands for CquiOR5 were linalool, PMD, and linalool oxide. CquiOR4 was predominantly expressed in antennae of nonblood fed female mosquitoes, with transcript levels significantly reduced after a blood meal. 2-Phenylethanol showed repellency activity comparable to that of DEET at 1%. RNAi experiments suggest that at least in part 2-phenylethanol-elicited repellency is mediated by CquiOR4 activation."
Meanwhile, Leal is gearing up for the 2019 Entomological Society of America (ESA) meeting in St. Louis, Mo., where he will deliver the Founders' Memorial Award Lecture on “Tom Eisner — An Incorrigible Entomophile and Innovator Par Excellence,” at the awards breakfast on Tuesday, Nov. 19.
ESA officials selected Leal, an ESA fellow and internationally recognized chemical ecologist, for the global honor. Leal is the first UC Davis scientist selected to present the Founders' Memorial Lecture, although medical entomologist Shirley Luckhart of the University of Idaho, formerly of UC Davis, delivered the lecture in 2018.
The 7000-member ESA is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. ESA, founded in 1889, is headquartered in Annapolis, Md.
Naoki Yamanaka, an assistant professor at UC Riverside (UCR), is known for his innovative and creative research. In fact, the National Institute of Health (NIH) just awarded him a $2.4 million grant in its High-Risk, High-Reward Research Program to study the role of steroid hormone transporters in insect development and reproduction. A UCR news release pointed out that he will "translate that knowledge into new ways to combat the spread of mosquitoes, which are among the deadliest animals on the plant."
Fast forward to today--actually next week! And this time, it's about fruit flies. Steroid hormone transporters in fruit flies.
Yamanaka will discuss "A Membrane Transporter Is Required for Steroid Hormone Intake in Drosophila" at the UC Davis Department of Entomology and Nematology seminar, set from 4:10 to 5 p.m., Wednesday, Oct. 24, in 122 Briggs Hall. Host is seminar coordinator and medical entomologist Geoffrey Attardo, assistant professor of entomology.
"Steroid hormones are a group of lipophilic hormones that are believed to enter cells by simple diffusion to regulate diverse physiological processes through intracellular nuclear receptors," Yamanaka explains. "We recently challenged this model in the fruit fly Drosophila melanogaster by demonstrating that a membrane transporter that we named Ecdysone importer (Ecl) is involved in cellular uptake of the steroid hormone ecdysone.Eci encodes an organic anion transporting polypeptide of the evolutionary conserved solute carrier organic anion superfamily. Results of our study may have wide implications for basic and medical aspects of steroid hormone research."
Yamanaka, who received his doctorate in biological sciences in 2007 from the University of Tokyo, says that his lab is "focused on identifying and characterizing neuroendocrine signaling pathways that regulate physiological and behavioral changes during insect development. Similar to humans, where physical and mental development during juvenile stage (puberty) is controlled by the neuroendocrine system, insects also have a sophisticated hormone signaling network that regulates their developmental transitions. Mainly by using fruit fly molecular genetic tools, we would like to understand what kind of hormones and receptors are involved in this system, how they work at the molecular level, and how such knowledge can be applied to develop new approaches to control animal development."
This is exciting research.
What exactly are "steroid hormones?" As author Sarah Nightingale explained in the UCR news release:
"Steroid hormones mediate many biological processes, including growth and development in insects, and sexual maturation, immunity and cancer progression in humans. After they are produced by glands of the endocrine system, steroid hormones must enter cells to exert their biological effects. For decades, the assumption has been that these hormones enter cells by simple diffusion, but preliminary work in Yamanaka's lab suggests a defined passageway controlled by proteins called membrane transporters."
Said Yamanaka: "The overall goal of this project is to challenge the conventional paradigm in endocrinology that steroid hormones freely travel across cell membranes by simple diffusion. We will also screen chemicals that inhibit steroid hormone entry into cells, with the goal of developing new pest control reagents.”
The NIH High-Risk, High-Reward Research Program is quite competitive. This year NIH officials granted only 89 awards and they were to “extraordinarily creative scientists proposing highly innovative research to address major challenges in biomedical research.”
Yamanaka's research may lead to important pest control strategies for mosquitoes that transmit deadly diseases. As Nightingale explained: "Using the simple but powerful fruit fly model, his team will study how the insect steroid hormone ecdysone is transported in (and potentially out) of cells with the help of membrane transporters. Since ecdysone controls metamorphosis and molting as an insect moves from one stage of its life cycle to the next, blocking its transport could offer a new way to inhibit insect growth and development. The team will then study the same transport pathway in the mosquito that causes yellow fever, hoping to identify chemicals that inhibit steroid hormone transport as a pest control strategy. Worldwide, mosquito-borne diseases cause millions of deaths each year, with malaria alone causing more than 400,000 deaths, according to the World Health Organization."
Bottom line: “By targeting the membrane transporter from outside the cells, we may be able to circumvent common pesticide resistance machinery provided by proteins within the cells, such as detoxification enzymes and drug efflux pumps,” Yamanaka pointed out in the news release.
His seminar at UC Davis is the fifth in a series of fall seminars coordinated by Attardo. (Note: The Yamanaka seminar will not be recorded.)
Upcoming seminars include:
4:10 p.m., Wednesday, Oct. 31
Fred Wolf, assistant professor, UC Merced: (tentative title) "Drunken Drosophila and the Coding of Brain Plasticity"
Host: Joanna Chiu, associate professor and vice chair, UC Davis Department of Entomology and Nematology
4:10 p.m., Wednesday, Nov. 7
Lark Coffey, assistant professor in the Department of Pathology, Microbiology and Immunology, UC Davis School of Veterinary Medicine: "Zika Virus in Macaques, Mice and Mosquitoes: Contrasting Virulence and Transmissibility in Disparate Hosts"
Host: Geoffrey Attardo