Project description:The responses of the transcriptome of Synechocystis PCC 6803 to UV-irradiation were measured at time points over 36 h. Irradiation was provided by Sylvania soft white DuluzR compact fluorescent 23W bulbs (Osram Sylvania Ltd, Mississauga, Canada), a 20W RS UV-B medical light with a spectral maximum at 310 nm (model ‘TL’, Philips, Holland), and 15W black lights each with a spectral maximum at 368 nm (model F15T8-BL, General Electric, USA). Total quantum scalar irradiance was measured with a model QSL-100 meter (Biospherical Instruments Inc., San Diego, CA). The flux densities of the UV-A and UV-B components of the spectrum were measured with DIX series UV-B and 365A sensors, respectively, with a Spectroline DRC-100X digital radiometer (Spectronics Corporation, Westbury, NY). In these experiments full illumination represented a continuous photon flux density in the visible range of 330 μmol photons m-2 s-1, with UV-A and UV-B maxima of 3.8 x 10^6 and 0.8 x 10^6 mW m-2, respectively. All values reported were the incident fluxes within culture vessels at the immediate surface of the cell suspensions. Aliquot cultures (in duplicate) were harvested after 0, 15 min, 1 h, 3 h, 6 h, 12 h, 24 h and 36 h of UV-irradiation. For each time 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 time point) (Custom-commercial array : 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: UV-irradiation, desiccation, Synechocystis PCC 6803, cyanobacteria, time course, transcription
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).