- Author: Kathy Keatley Garvey
His seminar, part of the department's weekly seminars, is from 4:10 to 5 p.m., Wednesday, Feb. 13 in 122 Briggs Hall, off Kleiber Hall Drive. The title: "Understanding the Molecular Mechanisms Underlying Photoperiodic Time Measurement in Drosophila melanogaster."
"I will talk about the molecular mechanisms involved in seasonal adaptation in insects," Brieux said. "Overwintering insects undergo profound physiological changes characterized by an arrest in development and reproduction in adults, known as diapause. While the hormonal control of reproductive diapause is relatively well described it is still unclear how organisms interpret variations in photoperiod (daylength) and temperature to modulate their physiology in order to survive through unfavorable seasons."
"In this context I will present the progress we made in the characterization of a key mechanism signaling seasonal changes in insects and how it can promote our understanding of animal seasonal timing in a comparative framework. In addition, future work on this aspect is also expected to have a broad significance in understanding the evolutionary response of pest insects to rapid climate change."
Says Brieux: "Arguably, the most well recognized seasonal response in insects is the induction of overwintering diapause, which can be induced at different life stages, and is characterized by arrest in growth and reproduction. Since PPTM is critical to seasonal adaptation in insects, it has been studied extensively. Yet, the molecular and neuronal basis of the insect photoperiodic timer has evaded characterization."
The overall goal of this study, he says, is "to address the long-standing knowledge gap using the genetically tractable Drosophila melanogaster and the migratory butterfly, the monarch, Danaus plexippus, as complementary model."
"Specifically, we propose to investigate the mechanisms by which the seasonal timer interprets and signals changes in photoperiod to elicit downstream neuroendocrine and physiological responses in insects."
D. melanogaster "continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution," according to Wikipedia. "As of 2017, eight Nobel prizes had been awarded for research using Drosophila."
Brieux received his bachelor's degree in biology in 2009 and pursued a master's degree from Pierre and Marie Curie University, Paris, France. He finished his doctorate in 2014 with faculty members Line Duportets and Christophe Gadenne at Angers University, western France, where he investigated the role of hormones and biogenic amines in the behavioral response to the sex pheromone in the noctuid Agrotis ipsilon.
The postdoctoral scientist joined the Chiu lab in the spring of 2016. In addition to his passion for research, Brieuz is a talented photographer passionate about macrophotography. Check out his photos on his website.
Associate professor Joanna Chiu, a molecular geneticist and physiologist, serves as the vice chair of the UC Davis Department of Entomology and Nematology, and is a newly selected Chancellor's Fellow. Her research expertise involves molecular genetics of animal behavior, circadian rhythm biology, and posttranslational regulation of proteins.
- Author: Kathy Keatley Garvey
Those are some of the questions that Wolf asks. "We aim to find some of the molecular and neural circuit mechanisms that govern adult behavior in the fruit fly Drosophila."
Wolf, who holds a doctorate in molecular and cell biology from UC Berkeley, will speak on "Drinking Drosophila and Drunk Drosophila: Genes and Circuits for Simple Behaviors" at the next UC Davis Department of Entomology and Nematology seminar, set for 4:10 p.m., Wednesday, Oct. 31 in 122 Briggs Hall.
"How is motivation coded in a small brain?" Wolf asks. "How does a natural motivation like a thirst differ from drug-seeking in addiction? We use circuit mapping, genetics and behavior in Drosophila melanogaster to find out internal states combine with environmental information to select behavioral programs and suppress others."
Molecular geneticist Joanna Chiu, associate professor and vice chair of the UC Davis Department of Entomology and Nematology, will introduce the speaker and serve as the host. Medical entomologist Geoffrey Attardo coordinates the fall seminars.
The Drosophila fly nervous system is remarkable. Wolf says it's "a million-fold simpler than ours, yet flies are capable of carrying out remarkably sophisticated tasks that are modified by past experience and internal states. However, the biological bases for even simple behavioral actions that serve as models for more complex tasks remain mysterious. Understanding how circuits function in a model organism where rapid progress can be made with highly sophisticated tools is likely to provide insight into how more complicated brains work."
No wonder that Drosophila melanogaster, is a favorite model organism among biomedical researchers.
"There are many technical advantages of using Drosophila over vertebrate models; they are easy and inexpensive to culture in laboratory conditions, have a much shorter life cycle, they produce large numbers of externally laid embryos and they can be genetically modified in numerous ways," according to Barbara Jennings in ScienceDirect.com. "Research using Drosophila has made key advances in our understanding of regenerative biology and will no doubt contribute to the future of regenerative medicine in many different ways."
"Over the past four decades," Jennings points out, "Drosophila has become a predominant model used to understand how genes direct the development of an embryo from a single cell to a mature multicellular organism." Indeed, numerous scientists have won Nobel Prizes for their research on the fruit fly.
What does the scientific name, Drosophila melanogaster, mean? Drosophila means "dew lover" and melanogaster means "dark gut."
- Author: Kathy Keatley Garvey
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.
