In most organisms, cell cycle progression requires highly controlled mechanisms for regulating appropriate level and timing of gene expression. During my PhD, I studied Caulobacter crescentus cell cycle transcription and I used forward genetic approaches to unravel the control of promoter activity by conserved cell-cycle transcriptional regulators and identify possible conservation of those mechanisms. First, I showed that environmental cues and the conserved alarmone (p)ppGpp can overcome the loss of the GcrA/CcrM pair, one of the three transcriptional modules implicated in C. crescentus cell cycle, by correcting the levels of the cell cycle response regulator CtrA. Second, I discovered a molecular determinant within the DNA-binding domain of CtrA that is required to execute the switch from late S- to G1- phase promoters and to reprogram CtrA in stationary phase cells accumulating (p)ppGpp. Finally, my work unveils a new conserved alphaproteobacteria RNA Polymerase co-factor implicated in the control of cell cycle transcription and possibly, in the response to certain antibiotic treatments.