DISSECTION OF EUKARYOTIC TRANSMEMBRANE SIGNALING USING CHLAMYDOMONAS

Novel insights and surprises are often generated when investigators ch oose an organism that permits a new approach to a problem. For example , secretory and cell-cycle mutants in yeast have provided quantum leap s in elucidating these processes. Similarly, genetic systems are provi ding exciting new insights into signal transduction. The 'green yeast' Chlamydomonas has the potential to be a particularly rich organism fo r genetic analysis of signal transduction because, although unicellula r, it has several interesting behaviours, which are discussed in this article by Lynne Quarmby and Criss Hartzell. Phototaxis results from t he transduction of a light signal received by the eyespot to changes i n flagellar beat. The mating reactions, which culminate in the fusion of gametes, are initiated in response to adhesion of flagellar protein s. Deflagellation, or flagellar shedding, is an acute response to a va riety of stimuli. Molecular genetic analysis of behavioural mutants is providing new directions for understanding signal integration and seg regation.