Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now quantified and mapped the functional units of the olfactory center in the brains of vinegar flies responsible for the perception of odors. They found out that the so-called olfactory glomeruli in the antennal lobe, the insect analogue of the olfactory bulb of mammals, differ from each other in their architecture. The morphology and the structure of these spherical brain units provide information about the ecological relevance of the odors they process, especially with regard to the flies’ odor-guided behavior.
When insects search for food, a sexual mate or the ideal place for laying eggs – somewhere where the hatching larvae have a good chance to survive – they have to rely on their sense of smell. They use their olfactory organs, the antennae, to detect odor molecules in their environment.
These odors are processed in the so-called antennal lobe, the actual olfactory center of the insect brain, which consists of spherical structures: the olfactory glomeruli. Here, inside the olfactory glomeruli, different groups of olfactory neurons form conjunctions or synapses which enable different environmental odors to be processed.
Until now, scientists had assumed that olfactory glomeruli share a pretty homogeneous architecture and that particular functions of the different glomeruli can be attributed primarily to special olfactory receptors on the membranes of the olfactory sensory neurons.
A research team of the Department of Evolutionary Neuroethology has now shown for the first time that the neuronal composition of each glomerulus is unique and highly specific. “Each glomerulus processes different odors in a unique way. The odors, on the other hand, differ in their impact on the behavior of the vinegar flies,” explains Silke Sachse, the leader of the study.
The researchers scrutinized the neuronal architecture of the olfactory glomeruli in the vinegar fly Drosophila melanogaster and linked the morphological differences they observed to the respective functions. They labeled different neurons in single glomeruli, and counted and anatomically described these. In order to achieve this, they used transgenic Drosophila lines which expressed the photoactivatable green fluorescent protein (PA-GFP) in the neurons and high-resolution confocal microscopy.
“As assumed, but until now not experimentally proven, glomeruli which contained many olfactory sensory neurons were generally bigger than were the glomeruli with fewer olfactory sensory neurons. This means that the anatomical shape of a glomerulus already provides information about how sensitive it will respond to a certain odor,” Veit Grabe, one of the first authors of the study, reports. The scientists also investigated whether there were any differences between male and female flies: Glomeruli which processed the Drosophila sex pheromones were bigger in males which were able to perceive the female attractants from large distances.
Moreover, the researchers counted the so-called projection neurons which are responsible for the transmission of odor stimuli to higher regions of the olfactory system. Glomeruli containing highly specific olfactory sensory neurons – namely, those which process only one single odor – seem to exhibit more projection neurons than glomeruli which process many different odors. More projection neurons make sure that information is transferred to higher brain regions in a faster and more reliable way to result in rapid odor-guided decisions.
In order to link the morphology of a glomerulus to its function, the research team determined another important parameter by means of electrophysiological analysis: “Lifetime sparseness” indicates how many different odors can activate an olfactory receptor. If a receptor is activated by a large variety of odors, it has very low “sparseness” and is therefore a very broad-range receptor. The higher the “sparseness” of a receptor, the fewer odors it is able to perceive.
An extreme case would be a highly specific receptor which responds only to a single odor. Odors which are very attractive to vinegar flies include their own pheromones, but also odors which provide clues about where to find a food source, such as overripe fruit. Some of these attractive odors may elicit oviposition in females, because they provide information about a place where larvae can hatch and have a good chance to survive. However, important odors may also be deterrents – and warning signals – because they contain information about lethal dangers, such as toxic substances in a potential food source or parasites.
“The complete quantitative mapping of all olfactory sensory neurons linked together in each olfactory glomerulus helped us to create an extended morphological basis for a better understanding of the role and function these units in the olfactory system have,” co-author Amelie Baschwitz summarizes.
Because these new insights are not limited to the vinegar fly, and may also apply to other animals or even humans, they have far-reaching significance. [KG/AO]
Grabe, V., Baschwitz, A., Dweck, H. K. M., Lavista-Llanos, S., Hansson, B., Sachse, S. (2016). Elucidating the neuronal architecture of olfactory glomeruli in the Drosophila antennal lobe. Cell Reports. DOI: 10.1016/j.celrep.2016.08.063
Dr. Silke Sachse, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Tel. +49 3641 57-1405, E-Mail email@example.com
Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail firstname.lastname@example.org
Download high-resolution images via http://www.ice.mpg.de/ext/downloads2016.html
http://www.ice.mpg.de/ext/index.php?id=evolutionary-neuroethology&L=0 Department of Evolutionary Neuroethology
Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy