Project description:The transcriptome approach was used to characterize the global change (2 Fe concentrations) in Synechocystis gene expression in response to continuous iron starvation, compared to standard medium (17 microM). For iron depletion, exponentially growing cells were washed in Fe-free medium, and grown for 48 hrs under standard conditions in liquid medium cotaining either 1 mM or 2 mM of ferric ammonium citrate. Then, cells were washed, and resuspended in Fe-free medium (Fe contaminations 0.5 microM) and grown for another 48 hrs period. For each concentration point, total RNA were isolated from stressed and unstressed cells, reverse-transcribed, differentially labelled (dye swapped), hybridized together (stressed versus unstressed samples) and analyzed with DNA glass microarrays (two slides per each concentration point) (Custom-commercial array : IntelliGeneTM CyanoCHIP version 2.0, TAKARA). To identify differentially expressed genes, the median of the normalized ratio of Cy5/Cy3 intensity was calculated for each spot of the replicated dye-swap. The results of the analysis were carefully examined to exclude the dye effect between the 2 Cy-swapped arrays. Keywords: stress responses
Project description:We compared transcriptomic changes, 5'-triphosphorylated (TSS) and 5'-monophosphorylated (PSS) RNA ends of different strains of the cyanobacterium Synechocystis sp. PCC6803. Comparison encompassed wild-type Synechocystis (WT), a strain overexpressing RNase E and RNase HII (rne(WT)) and a strain overexpressing 5’-sensing-deficient RNase E and RNase HII (rne(5p)). Analysis of changing 5'-monophosphorylated ends revealed 5’ sensing depedent processing sites on a transcriptome-wide level.
Project description:Cyanobacteria, photoautotrophic prokaryotes, contribute significantly to the global photosynthesis and require large amounts of the essential micronutrient iron in order to maintain their Fe-rich photosynthetic apparatus. Here we use the model organism Synechocystis sp. PCC 6803 (later referred to Synechocystis) in both, standard and iron stress conditions, to study transcription and post-transcription regulation in iron deprivation. Although iron is one of the most abundant metals on earth, it is not soluble under aerobic conditions. Thus Synechocystis had to find ways to overcome iron deficiency. At the same time, however, free intracellular iron needs to be kept at permissive levels, as it becomes toxic under aerobic conditions by producing reactive oxygen species. For these reasons, complex regulatory networks have evolved to tightly control intracellular iron concentrations, ensuring its essential function yet avoiding cellular damage (Pierre Cornelis et al). In a previous study, we investigated iron deprivation in Synechocystis using customised amplification library for the analysis of global gene expression in the unicellular cyanobacterium (Hernández-Prieto et al, 2012; Georg et al, 2017),(Georg et al, 2017) but it is still little known about RNA stability in this organism. We now extend this study through a transcriptome wide half-life analysis in Synechocystis grown under standard and iron-limiting conditions using oligonucleotide microarrays that detect both protein-coding and non-coding transcripts (ncRNA). We used the antibiotic Rifampicin to stop the transcription. Samples were taken at time points 0 min (before the addition of rifampicin) and in a time series of 2 min, 4 min, 8 min, 16 min, 32 min and 64 min after its addition.