Tag Archives: #flies

What Happens In the Brain Of Flies and Maybe, People when They Choose Their Food? (Neuroscience)

Flies have discriminating taste. Like a gourmet perusing a menu, they spend much of their time seeking sweet nutritious calories and avoiding bitter, potentially toxic food. But what happens in their brains when they make these food choices?

Yale researchers discovered an interesting way to find out. They tricked them.

In a study that could also help illuminate how people make food choices, the researchers gave hungry fruit flies the choice between sweet, nutritious food laced with bitter quinine and a less sweet, but not bitter, food containing fewer calories. Then, using neuroimaging, they tracked neural activity in their brains as they made these tough choices.

So which won? Calories or better taste?

“It depends on how hungry they are,” said Michael Nitabach, professor of cellular and molecular physiology, genetics, and neuroscience at Yale School of Medicine and senior author of the study. “The hungrier they are, the more likely they will tolerate bitter taste to obtain more calories.”

But the real answer to how flies make these decisions is a little more complex, according to the study published July 5 in the journal Nature Communications.

According to the research team, led by Preeti Sareen, associate research scientist at Yale, flies relay sensory information to a portion of their brain called the fan-shaped body, where signals are integrated, triggering what amounts to the insect version of an executive decision. The researchers found that patterns of neuronal activity in the fan-shaped body change adaptively when novel food choices are introduced, which dictates the fly’s decision over what food to eat.

But researchers went a step further. And things got even stranger. They found they could change a fly’s choice by manipulating neurons in areas of the brain that feed into the fan-shaped body. For example, when they caused a decrease in activity in the neurons involved in metabolism, the found that it made hungry flies choose the lower calorie food.

“It is one big feedback loop, not just top-down decision making,” Nitabach said.

And this is where there are connections to food choices of humans, he said. Neural activity in both a fly’s brain and a human’s brain are regulated by the secretion of neuropeptides and the neurotransmitter dopamine, which in humans helps regulate sensations of reward. Changes in this network may alter how the brain responds to different types of food. In other words, neurochemistry may sometimes dictate food choices we think we are making consciously.

“The study provides a template to understand how it is that things like hunger and internal emotional states influence our behavior,” Nitabach said.

Sareen and Li Yan McCurdy, a graduate student at Yale School of Medicine, are co-authors of the paper.

Reference: Sareen, P.F., McCurdy, L.Y. & Nitabach, M.N. A neuronal ensemble encoding adaptive choice during sensory conflict in Drosophila. Nat Commun 12, 4131 (2021). https://doi.org/10.1038/s41467-021-24423-y

Provided by Yale University

Rock-a-bye fly: Why Vibrations Lead to Sleepiness (Biology)

Researchers discover that gentle vibration can induce sleep in flies through a simple form of learning.

It is common practice to rock babies to sleep. Children and grownups also get drowsy during long car rides. There is something about gentle mechanical stimuli that makes humans of all ages sleepy. Sleep in fruit flies is very much like human sleep, and you can learn a lot about human sleep by studying how fly sleep is regulated. In research published in Cell Reports on December 1st, 2020, researchers report that flies fall asleep during vibration through a simple form of learning called habituation.

Illustration. Image Credit: Dr. Kyunghee Koh, Thomas Jefferson University.

“Babies like to be rocked to sleep, but the neural mechanisms underlying this well-known phenomenon remain largely a mystery. We wanted to establish the fruit fly as a model system to study the mechanisms of sleep induction by mechanical stimulation,” says Kyunghee Koh, PhD, associate professor of neuroscience at the Vickie & Jack Farber Institute for Neurosciences and the Synaptic Biology Center at Thomas Jefferson University and senior author on the study.

The researchers found that flies sleep longer during vibration and are less responsive to light pulses that would otherwise wake the flies. Also, they are more awake after vibration, suggesting they have accumulated “sleep credit.” In other words, they act as if they slept more than they need to during vibration, which allows them to function well with less sleep afterward.

These findings suggest that vibration-induced sleep is similar to regular sleep and serves some of their vital functions. They found that how much extra sleep flies get during vibration depends on the flies’ genetic background as well as the vibration frequency and amplitude. Dr. Koh’s group also learned that multiple sensory organs are involved in the process.

Interestingly, vibration initially makes flies more active than usual, but gradually puts them to sleep. Also, the ability to go to sleep improves when exposure to vibration is repeated several times, implicating habituation, a form of simple learning. “Flies learn over time that vibration is not threatening, which lowers their reaction to stimulation that would otherwise make them alert,” says Dr. Koh. Suppression of alertness appears necessary for vibration-induced sleep because mutant flies with increased dopamine levels that make them more alert do not fall asleep with vibration.

It is yet unclear whether similar mechanisms are at work in humans. But Dr. Koh says, “further investigation may help us develop and optimize sensory stimulation as a sleep aid for humans. Our findings suggest it would be worthwhile to personalize the stimulus parameters for each individual over several sessions.”

However, her team’s initial goals are to learn more about the underlying neural mechanisms using the fruit fly as a model system. They plan to identify specific neurons in the fly brain involved in the process and determine whether vibration-induced sleep functions like normal sleep to enhance memory and longevity and whether repetitive stimulation of other senses (e.g., sight and smell) can also induce sleep.

This work was supported by NIH grants R01NS086887 and R01NS084835, a predoctoral fellowship from the Portuguese Foundation for Science and Technology, and funds from Jefferson Synaptic Biology Center.

Article Reference: Arzu Öztürk-Çolak, Sho Inami, Joseph R. Buchler, Patrick D. McClanahan, Andri Cruz, Christopher Fang-Yen, and Kyunghee Koh, “Sleep Induction by Mechanosensory Stimulation in Drosophila,” Cell Reports, DOI: 10.1016/j.celrep.2020.108462, 2020.

Media Contact: Edyta Zielinska, 267-234-3553, edyta.zielinska@jefferson.edu.

Provided by Thomas Jefferson University

After 100 years, Cornell University Plant Pathologists Revisit Fire Blight Hypothesis (Botany)

Historically credited as being the first bacterium ever characterized as a plant pathogen, fire blight is a bacterial disease that leads to significant losses of pear and apple. The role of insects in the spread of this disease has been long studied. In a new study, plant pathologists based at Cornell University and Cornell AgriTech take a hypothesis that has been more or less ignored for 100 years and provided support for its validity.

Fly feeding on the ooze droplet in the experimental chamber. ©Matthew Boucher

According to first author Matthew Boucher, the study describes a long hypothesized but never experimentally supported transmission mechanism for fire blight. Boucher and colleagues show that flies in an apple orchard can acquire the bacterial agent (Erwinia amylovora) of fire blight from sugary droplets exuding from diseased apple trees and subsequently transmit the bacterium to uninfected shoots so long as those shoots are damaged in some way.

“This transmission mechanism is mechanical, the bacterium does not appear to have a close evolutionary relationship with any given insect and may seem inefficient to an unsuspecting observer,” explained Boucher. “However, we show that the massive populations of E. amylovora in the sugary droplets exuding from trees allow flies to acquire enough bacteria for the population to persist in and on flies for as long as seven days in some cases.”

Flies can continually shed bacteria over the course of those seven days, resulting in multiple opportunities for a single insect to initiate an infection.

“Demonstrating that bacterial populations can survive within the insect is important because previous research largely discounted E. amylovora survivability within an insect.” More research is needed, especially under field conditions, but this is an exciting step toward understanding the diversity of interactions between plants, insects, and phytopathogens.

“We also show that insects do not need to have intimated, co-evolved relationships with plant pathogens to be important agents in the disease cycle. There are only one or two similar pathogens in documented research, but there are likely more out there that need to be studied to advance our knowledge of this end of the disease-vector spectrum,” Boucher said when asked what makes his work groundbreaking. “As a collective work, we show the importance of integrating historical literature into modern research and revisiting topics and hypothesis that may not have been technologically feasible to investigate when they were first proposed.”

This work is a foundational study that will provide excellent context for future researchers interested in the topic. For more information, read “Interactions Between Delia platura and Erwinia amylovora Associated with Insect Mediated Transmission of Shoot Blight” published in PhytoFrontiers.

References: Matthew Boucher, Rowan Collins, Kayli Harling, Gabrielle Brind’Amour, Kerik Cox, and Greg Loeb, “Interactions Between Delia platura and Erwinia amylovora Associated with Insect Mediated Transmission of Shoot Blight”, APS, 2020. https://apsjournals.apsnet.org/doi/10.1094/PHYTOFR-08-20-0013-R https://doi.org/10.1094/PHYTOFR-08-20-0013-R

Provided by American Phytopathological Society

Time-keeping Brain Protein Influences Memory (Neuroscience)

Upsetting the brain’s timekeeping can cause cognitive impairments, like when jetlag makes you feel foggy and forgetful. These impairments may stem from disrupting a protein that aligns the brain’s time-keeping mechanism to the correct time of day, according to new research in fruit flies published in JNeurosci.

The core clock regulates distinct behaviors via discrete PDF targets: a proposed model. Localization of PDFR to the clock permits control of locomotor activity independently from control of memory. Signaling through PDFR in a population of interneurons extrinsic to both the clock and mushroom bodies (here shown as IN1) permits regulation of appetitive memory. We propose that, in place of PDF-PDFR signaling, PDF activation of a novel unidentified receptor (here called PDFR2) in a separate population of interneurons (IN2) is required for aversive memory. ©Flyer-Adams et al., JNeurosci 2020.

The brain contains ‘clock’ neurons that mold circadian behaviors and link them to cues from the environment, like light and seasonal changes. In fruit flies, the clock releases the peptide Pigment-dispersing factor (PDF) to synchronize the activity of the clock neurons and drive time-based behaviors like mating and sleep. PDF may also underlie memory formation, explaining the cognitive dysfunction that occurs when the clock is desynchronized from the environment.

Flyer-Adams et al. tested how well fruit flies with a functioning core clock but lacking the PDF output signal could learn. Flies without PDF had severely impaired memory . However, memory regulation by PDF likely occurs without direct signaling to the main memory structure of flies. These results suggest that PDF from the clock may promote normal memory throughout the day by acting as a timestamp to learning. The VIP pathway in humans may play a similar role.

References: http://dx.doi.org/10.1523/JNEUROSCI.0782-20.2020

Provided by The Society for Neuroscience

Research Provides A New Understanding Of How A Model Insect Species Sees Color (Biology)

Through an effort to characterize the color receptors in the eyes of the fruit fly Drosophila melanogaster, University of Minnesota researchers discovered the spectrum of light it can see deviates significantly from what was previously recorded.

Drosophila melanogaster under green and red fluorescence used as a marker to indicate the presence of inserted genes. ©Camilla Sharkey

“The fruit fly has been, and continues to be, critical in helping scientists understand genetics, neuroscience, cancer and other areas of study across the sciences,” said Camilla Sharkey, a post-doctoral researcher in the College of Biological Sciences’ Wardill Lab. “Furthering our understanding of how the eye of the fruit fly detects different wavelengths of light will aid scientists in their research around color reception and neural processing.”

The research, led by U of M Assistant Professor Trevor Wardill, is published in Scientific Reports and is among the first research of its kind in two decades to examine Drosophila photoreceptor sensitivity in 20 years. Through their genetic work, and with the aid of technological advancements, researchers were able to target specific photoreceptors and examine their sensitivity to different wavelengths of light (or hue).

Wild-type eye colouration in Drosophila (red eyes) and those with reduced screening pigment (orange eyes). ©Camilla Sharkey

The study found:

• all receptors — those processing UV, blue and green — had significant shifts in light sensitivities compared to what was previously known;
• the most significant shift occurred in the green photoreceptor, with its light sensitivity shifting by 92 nanometers (nm) from 508 nm to 600 nm; equivalent to seeing orange rather than green best;
• a yellow carotenoid filter in the eye (derived from Vitamin A) contributes to this shift; and
• the red pigmented eyes of fruit flies have long-wavelength light leakage between photoreceptors, which could negatively impact a fly’s vision.

Researchers discovered this by reducing carotenoids in the diets of the flies with red eyes and by testing flies with reduced eye pigmentation. While fly species with black eyes, such as house flies, are able to better isolate the long-wavelength light for each pixel of their vision, flies with red eyes, such as fruit flies, likely suffer from a degraded visual image.

“The carotenoid filter, which absorbs light on the blue and violet light spectrum, also has a secondary effect,” said Sharkey. “It sharpens ultraviolet light photoreceptors, providing the flies better light wavelength discrimination, and — as a result — better color vision.”

References: http://dx.doi.org/10.1038/s41598-020-74742-1

Provided by University Of Minnesota

Plant Guttation Provides Nutrient-Rich Food For Insects (Botany)

Small watery droplets on the edges of blueberry bush leaves are loaded with nutrients for many insects, including bees, wasps and flies, according to a Rutgers-led study, the first of its kind.

Droplets known as guttation, at the margins of a highbush blueberry leaf. © Credit: Pablo Urbaneja-Bernat

The study, published in the journal Proceedings of the Royal Society B: Biological Sciences, suggests that these droplets are an important but underexplored feature in plants, with profound implications for insects in agricultural and natural ecosystems.

“Our study shows for the first time that plant ‘guttation’ – fluid from sap secreted at the edges and tips of leaves – is a nutrient-rich source of food for insects,” said senior author Cesar Rodriguez-Saona, a professor and extension specialist in the Department of Entomology in the School of Environmental and Biological Sciences at Rutgers University–New Brunswick.

Many insects such as bees, wasps and flies drink the small droplets, which arise on nights with high levels of moisture in soil, and biologists considered them only as a source of water for insects. But the droplets are rich in carbohydrates and contain proteins that are essential for many insect species, according to Rodriguez-Saona.

In an experiment in Rutgers blueberry fields, insects with three different feeding lifestyles (an herbivore, a parasitic wasp and a predator) increased their ability to survive and reproduce when they fed on plant guttation droplets during their entire adult lives.

The droplets were also present in blueberry fields through the entire season and their presence doubled the abundance of beneficial insects – parasitic wasps and predators – that protect plants from pests. As a result, droplets might reduce the many problems caused by pests in crops, including invasive pests. And the researchers suggest that might occur in numerous crops where the droplet phenomenon is common, such as rice, wheat, barley, rye, oats, sorghum, corn, tobacco, tomatoes, strawberries and cucumbers, among others.

“These findings are important for the conservation of beneficial insects because they can find and feed on droplets when pollen, nectar, hosts or prey are scarce,” Rodriguez-Saona said.

Overall, the results demonstrate that the droplet phenomenon is highly reliable, compared with other plant-derived food sources such as nectar, and it increases the communities and fitness of insects, the study says.

Next steps include investigating the nutritional quality of droplets from other plant species and their fitness benefits for insects, as well as testing whether insecticides remain in droplets after being applied and affect beneficial insects.

References: Pablo Urbaneja-Bernat , Alejandro Tena , Joel González-Cabrera and Cesar Rodriguez-Saona, “Plant guttation provides nutrient-rich food for insects”, Proceedings Of the Royal Society B: Biological Sciences 2020, doi: https://doi.org/10.1098/rspb.2020.1080 link: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1080

Provided by Rutgers university