Transcriptional rewiring of the GcrA/CcrM bacterial epigenetic regulatory system in closely related bacteria

PLoS Genet. 2021 Mar 11;17(3):e1009433. doi: 10.1371/journal.pgen.1009433. eCollection 2021 Mar.


Transcriptional rewiring is the regulation of different target genes by orthologous regulators in different organisms. While this phenomenon has been observed, it has not been extensively studied, particularly in core regulatory systems. Several global cell cycle regulators are conserved in the Alphaproteobacteria, providing an excellent model to study this phenomenon. First characterized in Caulobacter crescentus, GcrA and CcrM compose a DNA methylation-based regulatory system that helps coordinate the complex life cycle of this organism. These regulators are well-conserved across Alphaproteobacteria, but the extent to which their regulatory targets are conserved is not known. In this study, the regulatory targets of GcrA and CcrM were analyzed by SMRT-seq, RNA-seq, and ChIP-seq technologies in the Alphaproteobacterium Brevundimonas subvibrioides, and then compared to those of its close relative C. crescentus that inhabits the same environment. Although the regulators themselves are highly conserved, the genes they regulate are vastly different. GcrA directly regulates 204 genes in C. crescentus, and though B. subvibrioides has orthologs to 147 of those genes, only 48 genes retained GcrA binding in their promoter regions. Additionally, only 12 of those 48 genes demonstrated significant transcriptional change in a gcrA mutant, suggesting extensive transcriptional rewiring between these organisms. Similarly, out of hundreds of genes CcrM regulates in each of these organisms, only 2 genes were found in common. When multiple Alphaproteobacterial genomes were analyzed bioinformatically for potential GcrA regulatory targets, the regulation of genes involved in DNA replication and cell division was well conserved across the Caulobacterales but not outside this order. This work suggests that significant transcriptional rewiring can occur in cell cycle regulatory systems even over short evolutionary distances.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Caulobacteraceae / genetics
  • Caulobacteraceae / metabolism
  • DNA Methylation
  • DNA Nucleotidyltransferases / genetics
  • DNA Nucleotidyltransferases / metabolism*
  • Epigenesis, Genetic*
  • Gene Expression Profiling / methods
  • Gene Expression Regulation, Bacterial*
  • Transcription, Genetic*


  • Bacterial Proteins
  • DNA Nucleotidyltransferases

Supplementary concepts

  • Brevundimonas subvibrioides

Grants and funding

This work was funded by United States National Science Foundation ( CAREER program award 1552647 awarded to PDC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.