Biology subjects

Bojkowska, K.

Publications and source records attributed to Bojkowska, K..

3 recordsLinked to original sources

bioRxiv2026

Genome replication and cell division control by the methylation-sensitive GcrA regulator in Agrobacterium tumefaciens

Bacteria with complex genomes including secondary chromosomes and/or megaplasmids face unique challenges when controlling their cell cycle: they not only need to coordinate genome replication with other cell cycle events such as cell growth and cell division, but also to synchronize the replication of different replicons. In Alphaproteobacteria, replication and maintenance of large extrachromosomal replicons are usually dependent on RepABC modules, as seen for the plant pathogen Agrobacterium tumefaciens. In this study, we demonstrate that the conserved GcrA protein is an essential methylation-dependent transcriptional regulator playing at least two critical roles during the A. tumefaciens cell cycle. First, GcrA is required for the on-time and synchronized firing of the three RepABC-dependent origins of replication of A. tumefaciens that are needed for chromosomal and megaplasmid replication. Second, GcrA triggers the expression of several essential cell division genes for the timely assembly of a functional divisome. These findings highlight how this conserved global regulator can control and then synchronize a variety of essential cell cycle events in Alphaproteobacteria with complex genomes, notably coordinating the maintenance of several RepABC-dependent replicons with cell division. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=47 SRC="FIGDIR/small/728657v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@c7f0f7org.highwire.dtl.DTLVardef@9cf8f1org.highwire.dtl.DTLVardef@19baa05org.highwire.dtl.DTLVardef@b73437_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

Cytosine methylation by ScmA contributes to the fitness of Caulobacter crescentus cells naturally expressing a Vsr-like protein

While methylated cytosines are known to play important roles in eukaryotes, their significance in bacteria remains poorly understood especially when they are added on genomes by DNA methyltransferases that are not parts of restriction-modification systems. The newly named ScmA protein of Caulobacter crescentus is one of these solitary cytosine methyltransferases. Here, we show that it methylates YGCCGGCR motifs introducing thousands of m5C bases on the C. crescentus genome. We also find that wild-type C. crescentus cells easily outcompete{Delta} scmA cells during competition experiments. Transcriptome comparisons and using single-cell fluorescent reporters reveal that a DNA damage response is turned on in a significant proportion of{Delta} scmA cells. We then show that this particular response is strictly dependent on the presence of a Vsr-like protein named VsrA. Eventhough the vsrA gene is surprisingly neither genetically linked with the scmA gene nor with another cytosine methyltransferase gene, VsrA is predicted to encode an endonuclease preventing m5C-to-T mutations. Fluorescence microscopy experiments then show that GFP-VsrA forms foci relatively frequently in stationary phase cells, which may correspond to active repair sites. We propose that VsrA may accidentally create double strand breaks when detecting mismatched bases on the genome of{Delta} scmA cells, leading to their observed loss of fitness. Thus, the presence of vsr-like genes can potentially stabilize genes encoding cytosine methyltransferases in bacterial genomes, providing a potential explanation for the relatively high prevalence of solitary cytosine methyltransferases in bacteria even if some of these do not appear to play an easily detectable regulatory role.

microbiology↗

bioRxiv2019

Functional integration of \"undead\" neurons in the olfactory system

Programmed cell death (PCD) is widespread during neurodevelopment, typically eliminating the surpluses of neuronal production. Employing the Drosophila olfactory system, we examined the potential of cells fated to die to contribute to circuit evolution. Inhibition of PCD is sufficient to generate many new cells that express neural markers and exhibit odor-evoked activity. These \"undead\" neurons express a subset of olfactory receptors that, intriguingly, is enriched for recent receptor duplicates and include some normally found in other chemosensory organs and life-stages. Moreover, undead neuron axons integrate into the olfactory circuitry in the brain, forming novel receptor/glomerular couplings. Comparison of homologous olfactory lineages across drosophilids reveals natural examples of fate changes from death to a functional neuron. Finally, we provide evidence that PCD contributes to evolutionary differences in carbon dioxide-sensing circuit formation in Drosophila and mosquitoes. These results reveal the remarkable potential of alterations in PCD patterning to evolve new neural pathways.

neuroscience↗