Synechocystis PCC6803 dose responses to iron starvation (96h).
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 Overall design: We made 2 concentration points of iron starvation (2 to 0.5 microM, or 1 to 0.5 microM). For each concentration point, we analyzed 2 arrays (dye swap).