Novel strategies for identification of clock genes in Neurospora with insertional mutagenesis.

As the molecular mechanism of circadian clocks has reached high complexity, the fungal model system, Neurospora crassa, is increasingly important for clock research. It offers the possibility of extensive biochemical experimentation and thorough description of circadian properties. Realization of the full potential is dependent on efficient, high-throughput methods. We have combined several protocols to develop abundant and inexpensive production of mutants, and subsequent identification of the affected gene. We applied a novel screening protocol and, after screening several hundred mutants, identified a known clock gene, frequency. Furthermore, the methods described here can easily be adapted to various insertional constructs (e.g., those with alternative selection markers or that facilitate overexpression) or combined with strains carrying clock-regulated reporter genes.

Combining theoretical and experimental approaches to understand the circadian clock.

This review is intended as a summary of our work carried out as part of the German Research Association (DFG) Center Program on Circadian Rhythms. Over the last six years, our approach to understanding circadian systems combined theoretical and experimental tools, and Gonyaulax and Neurospora have proven ideal for these efforts. Both of these model organisms demonstrate that even simple circadian systems can have multiple light input pathways and more than one rhythm generator. They have both been used to elaborate basic circadian features in conjunction with formal models. The models introduce the "zeitnehmer," i.e., a clock-regulated input pathway, to the conceptual framework of circadian systems, and proposes networks of individual feedbacks as the basis for circadian rhythmicity.