Investigation of the role of CarD in transcription initiation and the stringent response in Zymomonas mobilis

Abstract

In some prokaryotes, transcriptional regulator CarD stabilizes the open promoter complex during transcription initiation. As both a transcriptional activator and repressor, CarD can be used to coordinate gene expression to shape the transcriptome. CarD has also been previously implicated in the stringent response signaling pathway, through which bacteria reprogram their transcriptome to survive stress. Zymomonas mobili an ethanologenic bacteria with promise for biofuel production contains CarD, but its effect on initiation and the stringent response in Z. mobilis is unknown. To identify the role of CarD in Z. mobilis, we determined the genome-wide distribution of CarD relative to other transcription machinery, performed growth and survival assays during stringent response induction, and measured the effects of CarD and alarmone ppGpp on rRNA expression. Our results revealed that CarD is not essential for growth in Z. mobilis, but is important for ribosomal RNA biogenesis, relevant to both initiation and stringent control.