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The role of the Synechocystis sp. PCC 6803 homolog of the circadian clock output regulator RpaA in day–night transitions
Author(s) -
Köbler Christin,
Schultz SiriJasmin,
Kopp Dominik,
Voigt Karsten,
Wilde Annegret
Publication year - 2018
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14129
Subject(s) - biology , response regulator , circadian clock , histidine kinase , regulator , phototaxis , sasa , mutant , synechocystis , microbiology and biotechnology , gene , circadian rhythm , signal transduction , clock , cyanobacteria , biochemistry , genetics , bacteria , botany , neuroscience
Summary Cyanobacteria exhibit rhythmic gene expression with a period length of 24 hours to adapt to daily environmental changes. In the model organism Synechococcus elongatus PCC 7942, the central oscillator consists of the three proteins KaiA, KaiB and KaiC and utilizes the histidine kinase SasA and its response regulator RpaA as output‐signaling pathway. Synechocystis sp. PCC 6803 contains in addition to the canonical kaiAB1C1 gene cluster two further homologs of the kaiB and kaiC genes. Here, we demonstrate that the SasA‐RpaA system interacts with the KaiAB1C1 core oscillator only. Interaction with KaiC2 and KaiC3 proteins was not detected, suggesting different signal transduction components for the clock homologs. Inactivation of rpaA in Synechocystis sp. PCC 6803 leads to reduced viability of the mutant in light‐dark cycles, especially under mixotrophic growth conditions. Chemoheterotrophic growth of the ∆ rpaA strain in the dark was abolished completely. Transcriptomic data revealed that RpaA is mainly involved in the regulation of genes related to CO 2 ‐ acclimation in the light and to carbon metabolism in the dark. Further, our results indicate a link between the circadian clock and phototaxis.