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Forschungsarbeit

Chronobiology. Photoperiodism and circadian analysis of the fungus Neurospora crassa

von Tanja Radic (06.04.2009)

The scientific specialty of the Department I work in is chronobiology (from Latin chrono = time), i.e. a field of biology that examines how living organisms use the daily signals such as light-dark cycle and temperature cycles for adjusting their physiology and behaviour to the predictive changes in their environment. Human physiology, biochemistry, and the most of what happens in our bodies are rhythmic, showing strong day-night differences (Fig 1). Rhythms that vary according to the time of day, such as opening and closing of flowers and, in humans, the sleep-wake cycle and the changes in body temperature, are called circadian rhythms. There are also circannual rhythms, such as bird migrations, reproductive activity, and mammalian hibernation. Circadian rhythms are in part a response to daylight or dark, and annual cycles in part responses to changes in the relative length of periods of daylight. These rhythms are found in almost every living organism. In particular we study the molecular mechanisms how the circadian clock synchronizes living creatures to the environment, and even to the seasons' changing day lengths (phenomena known as photoperiodism).

The circadian clock of humans. The diagram depicts the various behavioural and physiological variables of someone who rises early in the morning[Bildunterschrift / Subline]: Fig 1: The circadian clock of humans. The diagram depicts the various behavioural and physiological variables of someone who rises early in the morning (Source: Wikipedia).

In my research, I focus on the interplay between circadian and annual rhythms in order to understand the molecular mechanism of photoperiodism. Photoperiodism can be defined as the developmental responses of an organism to the relative lengths of the light and dark periods. The effect of the length of day and night is enormous, just think of winter depression, which is more common in northern than in southern countries. Not only the health is influenced by the varying photoperiod, but also the reproduction and many other responses found in plants and animals are governed by the length of the day. Although much is known about the physiological mechanisms behind photoperiodism in higher animals, little is known about the molecular and genetic mechanisms of this important and ubiquitous biological function. For this purpose we need an organism that is very simple, one whose circadian biology and genetics are well studied, and which is found in different parts of the globe. These criteria are all met in the filamentous fungus Neurospora crassa.

Collection of Neurospora crassa wild type strains present in our Lab. Each red dot (17) represents the geographical location of the respective wild type strain.[Bildunterschrift / Subline]: Fig 2: Collection of Neurospora crassa wild type strains present in our Lab. Each red dot represents the geographical location of the respective wild type strain. The Winter solstice is taken to show that wild type strains from different geographical locations sense different length of the day during the year. (The collection of N. crassa wild type strains was generously provided by Dr. D. Jacobson)

My study involves the characterization of wild type strains of this fungus coming from the different parts of the globe and how they adopt their circadian clock to different light-dark and temperature regimes recording to their geographical origin (Fig 2). The planned experiments combine the investigation of the phenotype, and elucidating the corresponding genotype.
Because of the enormous and predictable daily changes in the metabolism of each cell, insights into circadian clocks are essential. The suggestion that human health might be affected by the length, timing, or even color of light that we are exposed to, and that there are remarkable similarities in the main components of clocks across organisms - from invertebrates to mammals - my goal is to see which crucial factors are important in fungal perception of different day length and give an insight what might be influencing the human well-being and health on different geographical places.


Tanja Radic
* 1983

Stationen
  • 10/2002 - 07/2005
  • Bachelor Degree in Molecular Biology at the University of Padua, Italy
  • 10/2005 - 07/2007
  • Master Degree in Molecular Biology at the University of Padua, Italy
  • since 09/2007
  • PhD student at Institute for medical psychology, Department of Chronobiology, LMU Munich
  • since 11/2008
  • research scholarship in the Elite Network of Bavaria