Functional genomics and evolution of photosynthetic systems

Abstract

Many genes related to the circadian clock have been discovered and studied in Synechococcus elongatus PCC 7942, the model organism for cyanobacterial circadian rhythms. However, the partners of some known clock components are still unidentified, and undiscovered pathways are predicted to exist that connect the central clock to other cellular functions. Identification of all clock components in S. elongatus is necessary for fully elucidating molecular mechanisms of the cyanobacterial circadian clock, as well as the relationship of the circadian clock to metabolism and other essential cellular activities. We adopted a transposon-mediated in vitro mutagenesis and sequencing strategy to disrupt essentially every locus in the genome and screen each insertional mutant for altered circadian phenotypes in S. elongatus. The completion of the genome sequence by the Department of Energy Joint Genome Institute greatly facili- tated our functional genomics project, which is very close to the finish line with 88% of the genome mutagenized and more than 75% of loci screened for circadian function. Among the first 700 genes surveyed, 70 new clock loci were discovered that represent an array of functional categories.