Effect of clpX overexpression in Synechococcus

In the unicellular cyanobacteriuIn the cyanobacterium, Synechococcus elongatus PCC 7942, most genes show rhythmic expression controlled by the Kai-based clock under continuous light conditions (LL). Overexpression of clpX led to a decrease in kaiBC promoter activity, disruption of circadian rhythm, and eventually cell death. We found that overexpression of clpX upregulated mRNA levels of ribosomal protein subunits, after which expression of other genes containing the clock genes was decreased. Wild type (WT) and inducible clpX-overexpressor (ox-clpX) S. elongatus PCC 7942 strains were analyzed under continuous light (LL) using Affymetrix high-density oligonucleotide microarrays (GeneChip CustomExpress Arrays) representing predicted 2,515 protein-coding genes on the genome of Synechococcus elongatus PCC 6301, which can be used also to the almost homologous strain, S. elongatus PCC 7942: WT at hours 16 in LL (IPTG-free): WT under LL 20 in LL (addition of 100 µM IPTG for 4 hours): ox-clpX cells at hours 16 in LL (IPTG-free): ox-clpX cells at hours 20 in LL (addition of 100 µM IPTG for 4 hours)