The circadian rhythm regulator RpaA modulates photosynthetic electron transport and alters the preferable temperature range for growth in a cyanobacterium

Cyanobacterial strains can grow within a specific temperature range that approximately corresponds to their natural habitat. However, how the preferable temperature range for growth (PTRG) is determined at the molecular level remains unclear. In this study, we detected a PTRG upshift in a mutant strain of Synechococcus elongatus PCC 7942 lacking the circadian rhythm regulator RpaA. Subsequent analyses revealed that RpaA decreases the electron transport from photosystem I to NADPH. The change in electron transport likely inhibits H2O2 generation under high-temperature conditions and contributes to the observed PTRG upshift in rpaA-deficient cells. The importance of the effects of the circadian rhythm regulator on the PTRG is discussed.

Automated summary

This study identified an upshift in the preferable temperature range for growth in a mutant strain of Synechococcus elongatus PCC 7942 lacking the circadian rhythm regulator RpaA. The decrease in electron transport caused by RpaA was found to inhibit H2O2 generation under high-temperature conditions, contributing to the observed upshift in the preferable temperature range. The importance of the circadian rhythm regulator on the preferable temperature range for growth was discussed.