The research focus of the WG Förster lies in the exploration of the circadian clock in Drosophila and selected other species
- Neuronal network of the circadian clock
- Synchronisation of the clock by light
- Role of Rhodopsins in Photo-, Mechano- und Thermosensoric
- Life-imaging in clock neurons
- Circadian clock and measurement of day length
- Photoperiodic adaptations
- meaning of the circadian clock for survival
To adapt to the seasonal changes in the environment of our planet, animals have evolved an internal circadian clock. For example the seasonal changing floral resources are a great challenge for the honeybee. The circadian clock is involved in processes like the honey bees’ time compensated sun compass orientation and the age related assignments of tasks in the bee hive. While foraging bees display strong circadian activity rhythms in their behavior, nursing bees show no such circadian rhythmicity.The molecular basis for this rhythm is a negative feedback loop consisting essentially of the four clock genes period, cryptochrome-m, cycle and clock. But other factors like the neuropeptide PDF (Pigment Dispersing Factor) seem to be also involved in the molecular clock of the honey bee.The main aim of my phd-project is to further characterize the circadian clock of honeybees (Apis mellifera) on the anatomical and molecular level and investigate the behavioral output of the honeybee clock by locomotor activity monitoring. Of special interest is here the locomotor activity of individual bees in the social context of a bee hive. Also part of my project is the characterization of the circadian clock of other insects which are research organisms in the collaborative areas of the SFB 1047. For example the solitary living red mason bee (Osmia rufa) and the pea aphid (Acyrthosiphon pisum).
The main task of the circadian clock is to time the activity such as food search, feeding, mating and egg laying at the right time of the day. Due to permanent changes of the environment such as day length the circadian clock has to be synchronized to the environment via appropriate Zeitgebers such as light and temperature. By timing the activity to the right time of the day the fly benefits from selective advantages. Neverthless, recent studies show that certain timing is possible without a functional circadian clock. Therefore my PhD-Thesis focuses on the activity pattern of wildtype flies and clock mutants to test whether the activity differs under natural-like laboratory and natural outdoor conditions. I will investigate the circadian clock and how the clock is influenced by light, temperature, humidity and nutrition. Furthermore I will analyse whether flies possessing a circadian clock benefit from advantages such as reproductive fitness and prolonged life-span, compared to flies without a functional circadian clock under natural outdoor conditions.
The circadian clock network of D. melanogaster consists of about 150 clock neurons which are located in the lateral and dorsal brain. Communication between these neurons as well as between clock neurons and putative clock output sites is thought to be mainly achieved by neuropeptides. The most important “clock” peptide is the pigment dispersing factor (PDF), which is highly conserved among different insect groups. Disturbance of the PDF circuit leads to a severe impairment of normal rhythmic behavior in Drosophila. The focus of my PhD thesis lies in the investigation and identification of other putative “clock” neuropeptides. Possible candidates are the Neuropeptide F (NPF), short Neuropeptide F (sNPF) and the Ion Transport Peptide (ITP). After manipulating peptide circuits – which is achieved mainly genetically – I investigate the impact on the clock function both on the behavioral and on the neuronal level. Methods I employ are immunocytochemistry, behavioral assays, live imaging and molecular genetics.
Many organisms, from bacteria to mammals, including humans, posses biological clocks that govern many aspects of their lives, both at the physiological and behavioral level and allow them to adapt to the rhythmically changing environment. Biological rhythms are driven by molecular oscillations that are generated in our bodies and kept in synchrony with the external world through stimuli, i.e light and temperature, the most important "Zeitgeber". Numerous aspects of the Drosophila melanogaster circadian clock are conserved in humans. An evident similarity is that mutations in the human genes Per2 and Ck1δ, orthologs of Drosophila per and Dbt respectively, cause a sleep associated pathology: the FASP, Familial Advanced Sleep Phase Syndrome. Because of this and other shared features between our and flies' clock mechanisms, D. melanogaster has been extensively used as model organisms. The circadian clock of the fruit fly Drosophila melanogaster relies on 7 groups of clock neurons per brain hemisphere which are bilaterally clustered in dorsal and lateral according to their positions in the brain. In these neurons, clock genes such as period (per), timeless (tim), vrille (vri) and PAR-domain protein1ε (pdp1ε) operate in interlocked feedback loops in which the clock proteins interact and thereby regulate their own transcription. So far, many studies contributed to the understanding of the particular functions of the different neurons and it is today quite clear that they are organized in very complicated network. With my work, I am investigating on how the different clusters of clock cells are influenced by the environmental stimuli and on the effect of specific combinations of light and temperature on the clock proteins oscillation within the master clock of wild-type and mutant flies.Publications
My main research interrest belongs to the neuronal network of Drosophilas circadian clock. To investigate this I work with behavior studies, mutant screenings, histology and bioimaging. In my Phd thesis I could allready work and illuminate parts of the dual oscillator system of Drosophila melanogaster. In future projects I would like to observe the individual neural oscillators of the fruitfly in vivo. This will be done over severeal circadian cycles. Another research focus is understanding the mechanisms that lead to synchronization of the internal clock of Drosophila. Here the focus is on a simulation of natural lighting conditions and their effect on the synchronization of the circadian Clock.
Mechano-, and photoreceptive cells are developmentally specified via transcription factors of the atonal and achaete-scute families across taxa. While the molecular basis of phototransduction is relatively well-studied, the molecular basis of mechanotransduction is poorly understood. Hearing is a specialized form of mechanotransduction. The antennal auditory organ of Drosophila, Johnston’s organ (JO), provides a valuable system to study mechanotransduction. During my Ph.D., we utilized the microarray technology to establish a catalogue of JO genes. Thereby we observed that well-known phototransduction genes such as rhodopsins, G-proteins, and TRP channels are also expressed in JO, fly’s auditory organ. Furthermore, mechanical measurements confirmed that many of these phototransduction genes (incl. Rh5, Rh6, arr2, inaD, glass, trp, trpl) actively contribute to hearing. Recent studies demonstrate that santa-maria and ninaE, phototransduction genes that were not identified by the screen, also affect hearing. In general, it seems like that phototransduction genes play an important role in hearing, but also in other sensory modalities such as thermosensation. These findings aroused my interest on the genetic parallels between different sensory modalities, especially between photo- and mechanotransduction. Currently, I am focusing on the parallels and differences between those sensory modalities - from the development to sensory processing. Therefore a variety of methods, incl. molecular biology, genetics, behavioral assays, and bioinformatics are used in my lab.
Insects undergo ‘diapause’ a physiological state characterized by low metabolic rate and arrest of growth, reproduction to survive the hardship of winter. It is well known that diapause is induced by shortening day-length in autumn. However, the mechanisms underlying day (or night) length measurement have remained elusive. I am trying to understand these mechanisms by using a judicious mixture of behavioural analysis, modelling, genetics and immuno-histochemistry in northern Drosophila species.