Synechococcus sp. PCC 7002 Transcriptome or Gene expression

Synechococcus sp. strain PCC 7002 is a unicellular, euryhaline cyanobacterium; it is a model organism for studies of cyanobacterial metabolism and has great potential for biotechnological applications. It exhibits an exceptional tolerance of high light irradiation and shows very rapid growth under optimal conditions. The habitats from which this and related organisms were isolated are subject to changes in several environmental factors, including light, nutrient supply, temperature, and salinity. In this study global transcriptome profiling via RNAseq has been used to perform a comparative and integrated study of global changes in transcript levels in cells grown at different temperatures, at different salinity and under mixotrophic conditions, when a metabolizable organic carbon source was present. Furthermore, the transcriptomes were investigated for cells that were subjected to a heat shock and that were exposed to oxidative stress. Lower growth temperatures caused relatively minor changes of the global transcriptome; the most prominent changes affected fatty acid desaturases. A heat shock caused severe changes of the global transcriptome pattern; transcripts for genes associated with major metabolic pathways declined and those for different chaperones increased dramatically. Oxidative stress, however, left the transcript pattern almost unaffected. Besides the increased expression of genes involved in compatible solute biosynthesis, Synechococcus sp. PCC 7002 showed increased mRNA levels for several genes involved in electron transport, which also generally increased under unfavorable growth conditions. Transcripts of two adjacent genes dramatically increased upon growth at high salinity; the respective proteins are putatively involved in coping with oxidative stress and in triggering ion channels. Only minor changes were observed when cells were grown at low salinity or when the growth medium was supplemented with glycerol. However, the transcriptome data suggest that cells must acclimate to excess reducing equivalents when a reduced C-source is present.