Project description:Like many other organisms, 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 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 two additional homologs of the kaiB and kaiC genes. Here we demonstrate that RpaA interacts with the core oscillator KaiAB1C1 of Synechocystis sp. PCC 6803 via SasA, similar to Synechococcus elongatus PCC 7942. However, interaction with the additional Kai homologs was not detected, suggesting different signal transduction components for the clock homologs. Inactivation of rpaA in Synechocystis sp. PCC 6803, lead to reduced viability of the mutant in light-dark cycles that aggravated under mixotrophic growth conditions. Chemoheterotrophic growth in the dark was abolished completely. In accordance, transcriptomic data revealed that RpaA is involved in the regulation of genes related to CO2‑acclimation and carbon metabolism under diurnal light conditions. Further, our results indicate that RpaA functions in the posttranslational regulation of glycogen metabolism as well, and a potential link between the circadian clock and motility was identified.
Project description:To identify novel phototransduction pathways in cyanobacteria, mutants defective for phytochrome-related proteins in Synechocystis sp. PCC 6803 that exhibit increased or decreased gene expression levels. were screened. Keywords: array-based
Project description:To investigate acclimation mechanisms employed under extreme high light conditions, gene expression analysis was performed using the model microalgae Synechocystis sp. PCC 6803 (PCC 6803) cultured under various light intensities. From the low to the mid light conditions, the expression of genes related to light harvesting systems was repressed, whereas that of CO2 fixation and of D1 protein turnover-related genes was induced. Gene expression data also revealed that the down-regulation of genes related to flagellum synthesis (pilA2), pyridine nucleotide transhydrogenase (pntA and pntB), and sigma factor (sigA and sigF) represents acclimation mechanisms of PCC 6803 under excessive high light conditions.
Project description:We found that cyanobacterial RNA polymerase possesses very efficient intrinsic proofreading ability. This ability allows model species of cyanobacteria, Synechocystis sp PCC 6803 to keep in vivo level of transcriptional mistakes close to that of E.coli.
Project description:We found that cyanobacterial RNA polymerase possesses very efficient intrinsic proofreading ability. This ability allows model species of cyanobacteria, Synechocystis sp PCC 6803 to keep in vivo level of transcriptional mistakes close to that of E.coli.
Project description:In cyanobacteria DNA supercoiling varies over the diurnal light/dark cycle and is integrated with temporal programs of transcription and replication. We manipulated DNA supercoiling in Synechocystis sp. PCC 6803 by CRISPRi-based knockdown of gyrase subunits gyrA, gyrB and overexpression of topoisomerase I (TopoI) topA and analyzed the transcriptional response to gyrase knock-downs (endpoint in triplicate) and topoisomerase I overexpression (endpoint in triplicate, and 19 time points time series before and after induction) in Synechocystis sp. PCC 6803 via RNA-seq of coding RNA. In detail, Illumina Ribo-Zero Plus rRNA Depletion Kit was used to remove the ribosomal RNA molecules from the isolated total RNA. Removal of rRNA was evaluated with the RNA Pico 6000 kit on the Agilent 2100 Bioanalyzer. RNA was free of detectable rRNA. Preparation of cDNA libraries was performed according to the manufacturer’s instructions for the TruSeq stranded mRNA kit (Illumina, San Diego, CA, United States). Subsequently, each cDNA library was sequenced on an Illumina NextSeq 500 system (2 x 75 nt PE high output v2.5).
Project description:The model cyanobacterium Synechocystis sp. PCC 6803 was used for a systematic survey on the number and types of antisense (as)RNAs. A tiled microarray was constructed with probes for both strands of the genes or intergenic spacers with candidate transcripts predicted by an algorithm and an equally sized and distributed control set. The resulting 102,739 individual probes cover an accumulated length of 1,441,146 nt or about 40% of the total chromosome sequence of Synechocystis 6803. Hybridization of this array with total RNA isolated from cultures raised under different growth conditions identified a high number of transcripts from intergenic spacers and in antisense orientation to known genes (natural cis-asRNAs). Extrapolated to the whole genome, around 10% of all open reading frames in Synechocystis 6803 may have a corresponding asRNA, suggesting a much more important role of chromosomally encoded asRNAs in bacteria then anticipated so far. Keywords: stress response 4 RNA hybridizations, 2 DNA controls. The raw data from the DNA hybridizations are in the GSE14410_DNA_1.txt and GSE14410_DNA_2.txt files.
Project description:Deciphering structure, function and mechanism of a new lysine methyltransferase cKMT1 in model cyanobacterium Synechocystis sp. PCC 6803
