Circadian Rhythms in Neurospora Crassa: Genetic Studies on Two Oscillator Models

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The fungus Neurospora crassa serves as a model system for studying the genetics and molecular biology of biological clocks. In this fungus the clock is expressed as areas of asexual spore formation (conidiation) alternating with areas of hyphal extension that show no conidiation. There is evidence that this clock has two oscillator loops. The products of the frq/wc loci are components of the first oscillator loop, but no components of the second have yet been described. The objectives of this project are to isolate new mutations affecting the clock and to classify the existing clock mutants according to their site of action. Both objectives are steps toward identifying components of the second oscillator. The study of the second oscillator can now be advanced by employing a new culture technique developed by the investigator. It allows the expression of the second oscillator in the absence of the first. The clock "null" strains (frq10, wc-1, wc-2) lack the first oscillator. When these strains are provided low (10-5M) concentrations of farnesol or geraniol (compounds related to intermediates in the steroid pathway), a clear, reproducible, and synchronous conidiation rhythm can be seen on Petri plates or growth tubes (normal length). New mutants in the clock system will be sought by screening for mutations that alter or abolish the rhythmicity of frq10 mutants grown on farnesol. If successful, these experiments will reveal new genes that affect the biological clock of this micro-organism. The insights gained from these genes and their products should lead to significant advances in our understanding of the functioning of biological clocks. The investigator is very active in training undergraduates, both through teaching their courses and mentoring their research projects in his laboratory.