Novel dinoflagellate clock-related genes identified through microarray analysis

In a genome-wide study of circadian gene expression, we constructed microarrays containing 3500 cDNAs from the dinoflagellate Pyrocystis lunula Schutt and compared the abundance of transcripts at circadian times separated by 12 h. About 3% of the unique genes screened were identified as circadian controlled, more than 50% of which could be identified with diverse known genes. Most were preferentially expressed in either early subjective day or late subjective night. Light exposures at times expected to induce phase shifts in the rhythm revealed 30 differentially expressed genes, including some potentially participating in photic entrainment and others in pathways connecting a central oscillator to output rhythms. Those that appeared in both screens were considered as possible core clock genes, but there were no similarities with such genes from other organisms. This is the first report of circadian regulation of transcript levels in a dinoflagellate.