- Author: Kathy Keatley Garvey
The paper, appearing online on the website of the Proceedings of the National Academy of Sciences (PNAS), solves a puzzle that scientists have tried to piece together for a long time.
The Chiu lab did it with the widely used model organism, Drosophila melanogaster, also known as the vinegar fly.
“This paper advances our understanding of how animals ‘sense' seasonal changes in day length and temperature to modulate their physiology and behavior in order to survive through seasonal variations in their environment,” Chiu said. “Specifically, we identified the protein EYA to be a key driver of seasonal changes in biology. By manipulating the level of EYA protein using transgenic technologies in specific neurons of the vinegar fly Drosophila melanogaster, we were able to disrupt the fly's ability to sense seasonal changes.”
“We were able to trick them into thinking that it is winter when it is actually summer time and vice versa,” Chiu said. “Interestingly, this protein is very conserved in other animals, including in birds and mammals, suggesting that the mechanism we are studying could be widely used in the animal kingdom.”
The paper, “EYES ABSENT and TIMELESS Integrate Photoperiodic and Temperature Cues to Regulate Seasonal Physiology in Drosophila,” is the work of the first author and postdoctoral fellow Antoine Abrieux, graduate students Yao Cao and Kyle Lewald, undergraduate researcher Hoang Nhu Nguyen, in collaboration with members of Dr. Yong Zhang's lab at the University of Nevada Reno. Associate Professor Joanna Chiu is the corresponding and senior author.
In their abstract, the seven-member team wrote: “Organisms possess photoperiodic timing mechanisms to detect variations in day length and temperature as the seasons progress. The nature of the molecular mechanisms interpreting and signaling these environmental changes to elicit downstream neuroendocrine and physiological responses are just starting to emerge. Here, we demonstrate that, in Drosophila melanogaster, EYES ABSENT (EYA) acts as a seasonal sensor by interpreting photoperiodic and temperature changes to trigger appropriate physiological responses. We observed that tissue-specific genetic manipulation of eya expression is sufficient to disrupt the ability of flies to sense seasonal cues, thereby altering the extent of female reproductive dormancy. Specifically, we observed that EYA proteins, which peak at night in short photoperiod and accumulate at higher levels in the cold, promote reproductive dormancy in female D. melanogaster.”
“Furthermore, we provide evidence indicating that the role of EYA in photoperiodism and temperature sensing is aided by the stabilizing action of the light-sensitive circadian clock protein TIMELESS (TIM). We postulate that increased stability and level of TIM at night under short photoperiod together with the production of cold-induced and light-insensitive TIM isoforms facilitate EYA accumulation in winter conditions. This is supported by our observations that tim null mutants exhibit reduced incidence of reproductive dormancy in simulated winter conditions, while flies overexpressing tim show an increased incidence of reproductive dormancy even in long photoperiod.”
Research in the Chiu lab focuses on the regulation of biological rhythms and their control over organismal physiology. Her expertise involves molecular genetics of animal behavior, circadian and seasonal biology, and posttranslational regulation of proteins.
By using Drosophila melanogaster as a model to study the mechanisms that regulate circadian clocks, Chiu has discovered new insights into the function of key proteins that control animal circadian clocks. She earlier identified new mechanisms that slow down or speed up the internal clock of vinegar flies and mechanisms that allow the internal clock to interpret food as timing cues--research that could help lead the way to alleviate human circadian and metabolic disorders.
“Besides being indispensable for the control of daily activities in animals, such as the sleep-wake cycle, locomotor activity, hormone circulation and food intake, defects in circadian rhythms and clock genes have also been implicated in a wide range of human disorders, including chronic sleep orders, various forms of depression, metabolic syndromes, as well as susceptibility to cancer and drug and alcohol addiction,” Chiu says.
D. melanogaster is widely used for biological research due to its rapid life cycle, simple genetics (only four pairs of chromosomes), and its large number of offspring per generation, according to Wikipedia. As of 2017, six Nobel prizes had been awarded for research using Drosophila.
The fly, a member of the family Drosophilidae, is a nuisance pest found worldwide in restaurants and other places where food is served.
First author and postdoctoral fellow Antoine Abrieux, an international scholar from France, holds a doctorate from Angers University, France. He joined the Chiu lab in spring 2016 to explore interactions between the clock and endocrine system underlying seasonal adaptation in Drosophila suzukii. He discussed his work at a UC Davis Department of Entomology and Nematology seminar in February 2019 about the molecular mechanisms involved in seasonal adaptation in insects.
- Author: Kathy Keatley Garvey
Her research expertise involves molecular genetics of animal behavior, circadian rhythm biology, and posttranslational regulation of proteins.
By using Drosophila melanogaster as a model to study the mechanisms that regulate circadian clocks, Chiu has discovered new insights into the function of key proteins that control animal circadian clocks. In particular, she has identified new mechanisms that slow down or speed up the internal clock of fruit flies and mechanisms that allow the internal clock to interpret food as timing cues--research that could help lead the way to alleviate human circadian disorders.
“Dr. Chiu is a prolific, phenomenal and talented scholar whose research is innovative, cutting-edge and groundbreaking,” said Helene Dillard, dean of the College of Agricultural and Environmental Sciences.
Steve Nadler, professor and chair of the Department of Entomology and Nematology, describes her as “a rising star.”
In announcing the Chancellor's Fellows, Chancellor Gary S. May said: “They've clearly made a mark both at UC Davis and within the academy generally. I have no doubt their contributions will continue to grow.” Each will retain the title for five years and receive a prize of $25,000 earmarked for research or scholarly work. Private donations to the UC Davis Annual Fund and the UC Davis Parents' Fund finance the program.
Chiu joined the Department of Entomology and Nematology in 2010 as an assistant professor and advanced to associate professor and vice chair in 2016. She received her bachelor's degree in biology and music from Mount Holyoke College, Mass., and her doctorate in molecular genetics in 2004 from New York University, New York. She served as a postdoctoral fellow from 2004 to 2010 in chronobiology (biological rhythms and internal clocks)--molecular genetics and biochemistry--at the Center for Advanced Biotechnology and Medicine, at Rutgers, the State University of New Jersey.
Major grants from the National Institutes of Health and the National Science Foundation fund Chiu's biological rhythms research.
In addition to her research in biological rhythms, Chiu also aims to leverage her expertise in genomics to address key issues in global food security. She is the principal investigator (PI) or co-PI on six grant awards from the State of California to research various fruit crops damaged by the spotted-wing Drosophila. At the time of her nomination, her publication record included 41 journal publications and book chapters, one U.S. Patent, and more than 3,235 journal citations (Google Scholar).
Chiu targets the spotted wing drosophila, Drosophila suzukii, first detected in North America in central California in August 2008. A native of Southeast Asia, the invasive species has already caused billions of dollars in damage to U.S. agriculture. Chiu took the lead role in sequencing the genome and is now heavily involved in finding new and more sustainable strategies to control the pest.
Chiu instigated the drive to obtain genomic data prior to its adaptation to a variety of local environments, which can differ in climate, pesticide use, natural enemies and types of fruits available. She played a leading role in establishing the SpottedWingFlyBase, a publicly available web portal documenting a variety of genomic databases for this species.
Chiu co-founded and co-directs (with professor Jay Rosenheim and associate professor Louie Yang) the campuswide Research Scholars Program in Insect Biology, launched in 2011 to provide undergraduates with a closely mentored research experience in biology. The program's goal is to provide academically strong and highly motivated undergraduates with a multi-year research experience that cultivates skills that will prepare them for a career in biological research.
Under her tutelage, many of Chiu's students are first authors of publications in prestigious journals. She continues to provide guidance and advice to undergraduate and graduate students and those who have embarked on their careers.
Former UC Davis graduate student Kelly Hamby, now assistant professor/Extension specialist in the Department of Entomology, University of Maryland, said Chiu “is so generous of her time and advice. Her office is always open to students, whether they are visiting high school students, undergraduates, or graduate students, her own students or someone else's. She carefully guides students throughout their experiments, directly providing technical training—side by side at the bench—while developing their critical thinking and communication skills. Joanna not only imparts excellent analytic and laboratory molecular skills to her students, but also commits to providing ongoing professional advice and development. Joanna's mentorship continues long after graduate and she leaves a lasting impression on students.”
“Joanna's teaching philosophy is clearly targeted towards the professional development of her students, modeling assignments on the activities of practicing scientists,” Hamby added.
The previous recipient from the Department of Entomology and Nematology was pollination ecologist Neal Williams, now a professor.
See list of this year's Chancellor's Fellows on UC Davis Dateline.