Genetic manipulation to overexpress rpaA altered photosynthetic electron transport in Synechocystis sp. PCC 6803

Abstract

Cyanobacteria are a group of prokaryotic organisms that perform oxygenic photosynthesis using a similar photosynthetic apparatus as is used in higher plants and eukaryotic algae. Cyanobacteria are also known to have a circadian rhythm. Here, we evaluated the effects on photosynthesis caused by the genetic manipulation of RpaA, which is a response regulator of a two-component regulatory system responsible for the signal output from circadian clocks. Using the unicellular cyanobacterium Synechocystis sp. PCC 6803, photosynthetic activities and transcript levels of photosystem I and photosystems II in the rpaA-overexpressing strain were measured, and it was found that the parameters, such as F/F, F'/F', qP, and ϕII, obtained from chlorophyll fluorescence analysis were decreased by rpaA overexpression. These results suggest that rpaA overexpression modified photosynthetic electron transport under normal light conditions. Thus, we demonstrated that RpaA regulates photosynthesis in cyanobacteria and can be a potential target of photosynthetic engineering in this cyanobacterium.

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

“…Specifically, RpaA is a circadian rhythm‐related transcription factor that affects gene expression patterns in a genome‐wide manner. However, previous studies demonstrated that genes encoding the components of two photosystems are basically not under the control of RpaA [37], which was consistent with the protein levels of D1 and CP1 in this study (Fig. 3C).…”

“…The results of earlier studies suggested that RpaA negatively affects PET in Synechocystis [37,38]. In the current study, RpaA decreased the electron transport from PSI to NADPH irrespective of the examined temperatures (Figs 2, 3A,B, 4, and 6A, Table 2).…”

For Whom the Clock Ticks: Clinical Chronobiology for Infectious Diseases

“…One reason for this belief was the idea that organisms duplicating more than once a day do not need a rhythm longer than their life cycle ( 36 ). In the 1980's, circadian rhythm was found present in cyanobacteria ( 37 – 39 ), photoautotrophic organisms that produce oxygen by photosynthesis as plants and eukaryotic algae ( 40 , 41 ). In cyanobacteria, photosynthesis occurs in daylight, whereas nitrogen production peaks during the night ( 42 ).…”

“…Regarding cyanobacteria, the central biochemical oscillator of their circadian rhythm is represented by three proteins encoded by the KaiABC cluster ( 10 , 46 , 47 ), SasA, CikA, and RepA, which control the timing training, and output of the cyanobacterial cell signaling process ( 48 ). Several studies have examined how functions the circadian loop of cyanobacteria ( 40 , 42 , 49 – 51 ). A theoretical model of the KaiABC oscillator suggests that ATP hydrolysis is a driving mechanism of phosphorylation oscillations and that the frequency of ATP hydrolysis in individual KaiC molecules is correlated with the circadian rhythm frequency ( 50 ) ( Figure 2 ).…”