Involvement of Cyanobacterial Phytochromes in Growth Under Different Light Qualitities and Quantities^¶

Abstract

Inactivation of the genes for the cyanobacterial phytochromes cph1 and cph2 in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 affected the growth of the cells under certain light conditions. Differences in growth were detected by recording growth curves and in competition experiments. Mutation of cph1 and cph2 resulted in different effects. The cph1− mutant strains exhibited a reduced growth rate under far‐red light (FRL), whereas the growth of the cph2− mutant strains was inhibited by red light (RL). The growth rate of a cphl−/cph2− double mutant was reduced under both RL and FRL. Furthermore, cph1−, cph2− as well as double‐mutant strains showed impaired growth under high‐light (HL) conditions. Acclimation of the photosynthetic apparatus of the mutants to RL, FRL and HL, as determined by pigment analysis, was similar to that of the wild type.

Cyanobacterial Phytochromes in Optogenetics

“…Growth of the cyanobacterium Synechocystis PCC 6803 in red (R) and far red (FR) light is regulated by Cph1 and Cph2 in an antagonistic method. Modification in Cph1 negatively affects the Synechocystis growth in FR light, further destruction of Cph2 hinders its growth in red light [33]. Mutation in Cph2 transformed the growth rate and exopolysaccharide biofilm formation, involved in the control of the principal energy metabolism [34].…”