Global transcriptional and circadian regulation in a halotolerant cyanobacterium Halothece sp. PCC7418

Substantial evidence has been accumulated about the molecular basis underlying halotolerance; however, insights into the regulatory networks for relevant genes and mechanisms of their interplay remain elusive. Here, we present a comprehensive transcriptome investigation, using RNA sequencing, of specific metabolic pathways and networks in a halotolerant cyanobacterium, Halothece sp. PCC7418, including the circadian rhythm profile. Dissecting the transcriptome presented the intracellular regulation of gene expressions, which was linked with ion homeostasis, protein homeostasis, biosynthesis of compatible solutes, and signal transduction, for adaptations to high-salinity environments. The efficient production and distribution of energy were also implicated in this acclimation process. Furthermore, we found that high-salinity environments had a dramatic effect on the global transcriptional expression regulated by the circadian clock. Our findings can provide a comprehensive transcriptome for elucidating the molecular mechanisms underlying halotolerance in cyanobacteria. Overall design: Halothece sp. PCC7418 cells growing in low salinity (0.5 M NaCl) or high salinity (2.5 M NaCl) were analyzed under continuous light (LL) by RNA-seq analysis. The cells were harvested at LL4, 10, 16, 22, 28, and 34 under LL condition.