Overexpression of lalA, a paralog of labA, is capable of affecting both circadian gene expression and cell growth in the cyanobacterium Synechococcus elongatus PCC 7942

In the cyanobacterium Synechococcus elongatus, LabA negatively regulates circadian gene expression under the control of Kai-protein-based clock. Here we conducted a molecular genetic analysis of lalA, a paralog of labA. Although a lalA loss of function mutant did not exhibit any apparent phenotype under our experimental conditions, lalA overexpression inhibited cell growth and decreased cell viability. Moderate lalA overexpression brought about abnormalities in circadian gene expression: reduced amplitude of kaiBC expression rhythm, and altered peak and trough timing of psbAI and kaiA expression rhythms. These results imply that lalA is capable of affecting circadian gene expression and cell growth.

► lalA is a paralog of the cyanobacterial clock-related gene labA.
► lalA overexpression reduced amplitude of circadian kaiBC expression.
► lalA overexpression advanced phases of circadian kaiA and psbAI expression.
► lalA overexpression affected cellular growth and viability.