Cytokinesis signals truncation of the PodJ polarity factor by a cell cycle-regulated protease
Ontology highlight
ABSTRACT:
ORGANISM(S): Caulobacter vibrioides
PROVIDER: GSE3144 | GEO | 2005/12/08
SECONDARY ACCESSION(S): PRJNA92975
REPOSITORIES: GEO
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Project description:Within the bacterial phylum of the Alphaproteobacteria many species show complex life cycles. Proper regulation of these life cycles requires cell cycle regulation pathways, one of which is the so-called CtrA pathway. Key factors in the CtrA pathway are the histidine kinases PleC and DivJ (located at opposite poles in the cell) and the response regulator DivK. Within the Alphaproteobacteria, stalked budding bacteria are even more asymmetric than most other representatives. How they regulate their cell cycle has not been studied before. Here, we investigated the transcriptional profiles of Hyphomonas neptunium cells lacking either PleC, DivJ or DivK and compared their profiles to that of wildtype cells. We found that the changes upon deletion of DivJ, PleC and especially DivK were smaller than expected from related organisms.
2022-01-01 | GSE134343 | GEO
Project description:Alphaproteobacteria stand out for their complex cell cycles, which are often regulated by the DivJ/PleC-DivK-DivL-CckA-ChpT-CtrA pathway. DivJ and PleC set up the polarity of the cell, thereby eventually leading to differential activation of the DNA-binding response regulator CtrA in the two nascent daughter cells. CtrA regulates replication and transcription of many genes, thereby ensuring that processes such as motility and cell division take place at the appropriate cell cycle stage. The cell cycle of the stalked budding alphaproteobacterium Hyphomonas neptunium culminates in an asymmetric cell division at the stalk-bud junction. Here, we investigate the role of the pathway from DivJ and PleC down to CtrA in this recently established model organism. Even though DivJ and PleC are localized to opposite poles, suggesting they are involved in polarity establishment inH. neptunium, DivJ, PleC and the other components of the upstream pathway (DivK and PleD) are not essential for cell cycle regulation. In contrast, the downstream part of the pathway starting from DivL is essential and involved in the regulation of important functions such as replication inhibition, cell division and motility, as shown by the identification of the (direct) regulon of CtrA. The overlap between the regulons of DivJ and PleC, DivK and CtrA is only partial, demonstrating that additional factors feeding into the pathway must be present in H. neptunium. Furthermore, unlike in other alphaproteobacteria, the regulation of CtrA throughout the cell cycle does not take place at the level of CtrA abundance in H. neptunium. All in all, the DivL-CckA-ChpT-CtrA pathway plays an essential role in the regulation of the complicated cell cycle ofH. neptunium, but several proteins feeding into CtrA remain undiscovered. The in-depth analysis of CtrA regulation in this stalked budding organism leads to hypotheses that might also hold in well-established model organisms such as Caulobacter crescentus.
2020-03-29 | GSE124953 | GEO
Project description:In the model organism Caulobacter crescentus, a network of two-component systems involving the response regulators CtrA, DivK and PleD coordinate cell cycle progression with differentiation. Active phosphorylated CtrA prevents chromosome replication in G1 cells while simultaneously regulating expression of genes required for morphogenesis and development. At the G1-S transition, phosphorylated DivK (DivK~P) and PleD (PleD~P) accumulate to indirectly inactivate CtrA, which triggers DNA replication initiation and concomitant cellular differentiation. The phosphatase PleC plays a pivotal role in this developmental program by keeping DivK and PleD phosphorylation levels low during G1, thereby preventing premature CtrA inactivation. Here, we describe CckN as a second phosphatase akin to PleC that dephosphorylates DivK~P and PleD~P in G1 cells. However, in contrast to PleC, we do not detect kinase activity with CckN. The effects of CckN inactivation are largely masked when PleC is present, but become evident when PleC and DivJ, the major kinase for DivK and PleD, are absent. Accordingly, mild overexpression of cckN restores most phenotypic defects of a pleC null mutant. We also show that CckN and PleC are proteolytically degraded in a ClpXP-dependent way well before the onset of the S phase. Surprisingly, known ClpX adaptors are dispensable for PleC and CckN proteolysis, suggesting the existence of adaptors specifically involved in proteolytic removal of cell cycle regulators. Since cckN expression is induced in stationary phase, depending on the stress alarmone (p)ppGpp, we propose that CckN acts as an auxiliary factor responding to environmental stimuli to modulate CtrA activity under suboptimal conditions.
2020-06-09 | GSE152025 | GEO
Project description:We demonstrate that successive cleavage events involving regulated intramembrane proteolysis (Rip) occur as a function of time during the Caulobacter cell cycle. The proteolytic substrate PodJ(L) is a polar factor that recruits proteins required for polar organelle biogenesis to the correct cell pole at a defined time in the cell cycle. We have identified a periplasmic protease (PerP) that initiates the proteolytic sequence by truncating PodJ(L) to a form with altered activity (PodJ(S)). Expression of perP is regulated by a signal transduction system that activates cell type-specific transcription programs and conversion of PodJ(L) to PodJ(S) in response to the completion of cytokinesis. PodJ(S), sequestered to the progeny swarmer cell, is subsequently released from the polar membrane by the membrane metalloprotease MmpA for degradation during the swarmer-to-stalked cell transition. This sequence of proteolytic events contributes to the asymmetric localization of PodJ isoforms to the appropriate cell pole. Thus, temporal activation of the PerP protease and spatial restriction of the polar PodJ(L) substrate cooperatively control the cell cycle-dependent onset of Rip.
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Project description:A conserved regulatory pathway directs developmental transitions and asymmetries in Agrobacterium tumefaciens. Core components of this coordination of division and development (CDD) pathway include two integrated phosphorelays. One of these phosphorelays includes at least four histidine sensor kinase homologues, DivJ, PleC, PdhS1, and PdhS2, and at least two response regulators, DivK and PleD. Previously we demonstrated that PdhS2 reciprocally regulates biofilm formation and swimming motility. In the current study we further dissect the architecture of the CDD pathway in A. tumefaciens with respect to PdhS2. We show that PdhS2-dependent effects on attachment and motility require the response regulator, DivK, but do not require PdhS2 autokinase or phosphotransfer activities. We also demonstrate that PdhS2 regulation of biofilm formation is dependent upon multiple diguanylate cyclases, including PleD, DgcA, and DgcB, implying that PdhS2 regulation of this process intersects with pathways regulating levels of the second messenger cyclic-di-GMP. Finally, we show that upon cell division a GFP fusion to PdhS2 dynamically localizes to the new pole of the bacterium suggesting that PdhS2 controls processes in the daughter cell compartment of predivisional cells. These observations suggest that PdhS2 negatively regulates DivK, and possibly PleD, activity to control developmental processes in the daughter cell compartment of predivisional cells, as well as in newly released motile daughter cells. Three biological replicates, independent RNA preparations, one dye swap.
2015-07-24 | E-GEOD-71267 | biostudies-arrayexpress
Project description:A conserved regulatory pathway directs developmental transitions and asymmetries in Agrobacterium tumefaciens. Core components of this coordination of division and development (CDD) pathway include two integrated phosphorelays. One of these phosphorelays includes at least four histidine sensor kinase homologues, DivJ, PleC, PdhS1, and PdhS2, and at least two response regulators, DivK and PleD. Previously we demonstrated that PdhS2 reciprocally regulates biofilm formation and swimming motility. In the current study we further dissect the architecture of the CDD pathway in A. tumefaciens with respect to PdhS2. We show that PdhS2-dependent effects on attachment and motility require the response regulator, DivK, but do not require PdhS2 autokinase or phosphotransfer activities. We also demonstrate that PdhS2 regulation of biofilm formation is dependent upon multiple diguanylate cyclases, including PleD, DgcA, and DgcB, implying that PdhS2 regulation of this process intersects with pathways regulating levels of the second messenger cyclic-di-GMP. Finally, we show that upon cell division a GFP fusion to PdhS2 dynamically localizes to the new pole of the bacterium suggesting that PdhS2 controls processes in the daughter cell compartment of predivisional cells. These observations suggest that PdhS2 negatively regulates DivK, and possibly PleD, activity to control developmental processes in the daughter cell compartment of predivisional cells, as well as in newly released motile daughter cells.
2015-07-24 | GSE71267 | GEO
Project description:Analysis of global transcriptional changes in H. neptunium cells lacking the cell cycle regulatory genes pleC, divJ or divK
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Project description:Although diminutive in size, bacteria possess highly diverse and spatially confined cellular structures. Two related alpha-proteobacteria, Sinorhizobium meliloti and Caulobacter crescentus, serve as models for investigating the genetic basis of morphologic variations. S. meliloti, a symbiont of leguminous plants, synthesizes multiple flagella and no prosthecae, whereas C. crescentus, a freshwater bacterium, has a single polar flagellum and stalk. The podJ gene, originally identified in C. crescentus for its role in polar organelle development, is split into two juxtaposed open reading frames, podJ1 and podJ2, in S. meliloti. Deletion of podJ1 interferes with flagellar motility, exopolysaccharide production, cell envelope integrity, cell division, and normal morphology, but not symbiosis. As in C. crescentus, the S. meliloti PodJ1 protein appears to act as a polarity beacon and localizes to the newer cell pole. Microarray analysis indicates that podJ1 affects the expression of at least 129 genes, the majority of which correspond to observed mutant phenotypes. The combination of phenotypic characterization, microarray analysis, and suppressor identification suggests that PodJ1 controls a core set of conserved elements, including flagellar and pili genes, the signaling proteins PleC and DivK, and the TacA transcriptional activator, while alternate downstream targets have evolved to suit the distinct lifestyles of individual species. Gene expression profiling of Sinorhizobium meliloti Rm1021 or its isogenic podJ1 deletion mutant, grown to mid exponential phase in rich medium, was performed using custom Affymetrix GeneChips.
2012-08-09 | E-GEOD-31325 | biostudies-arrayexpress
Project description:Although diminutive in size, bacteria possess highly diverse and spatially confined cellular structures. Two related alpha-proteobacteria, Sinorhizobium meliloti and Caulobacter crescentus, serve as models for investigating the genetic basis of morphologic variations. S. meliloti, a symbiont of leguminous plants, synthesizes multiple flagella and no prosthecae, whereas C. crescentus, a freshwater bacterium, has a single polar flagellum and stalk. The podJ gene, originally identified in C. crescentus for its role in polar organelle development, is split into two juxtaposed open reading frames, podJ1 and podJ2, in S. meliloti. Deletion of podJ1 interferes with flagellar motility, exopolysaccharide production, cell envelope integrity, cell division, and normal morphology, but not symbiosis. As in C. crescentus, the S. meliloti PodJ1 protein appears to act as a polarity beacon and localizes to the newer cell pole. Microarray analysis indicates that podJ1 affects the expression of at least 129 genes, the majority of which correspond to observed mutant phenotypes. The combination of phenotypic characterization, microarray analysis, and suppressor identification suggests that PodJ1 controls a core set of conserved elements, including flagellar and pili genes, the signaling proteins PleC and DivK, and the TacA transcriptional activator, while alternate downstream targets have evolved to suit the distinct lifestyles of individual species.
2012-08-10 | GSE31325 | GEO
Project description:During cytokinesis in the budding yeast Saccharomyces cerevisiae, contraction of the cytokinetic ring and primary septum synthesis by chitin synthase II (Chs2p) are coupled processes. Myosin II (Myo1p), is involved in the actomyosin ring formation, required for proper cytokinesis, while Chs2p is responsible for the chitin primary septum formation which is necessary to stabilize the cytokinetic ring during its contraction. Morphological phenotypes of myo1∆ and chs2∆ mutants are therefore similar particularly in that both are unable to complete normal cytokinesis. A comparison between the global mRNA transcription profiles of myo1∆ and chs2∆ strains was conducted using oligonucleotide microarrays to establish if these cytokinesis mutants exhibited similar mRNA expression patterns and signature profiles were later generated from gene set enrichment analysis (GSEA). Genetic experiments were conducted to further test predictions based on the GSEA results. As reported previously in myo1∆ strains, a significant number of protein biosynthesis and RNA processing genes that may be attributed to regulation by cell integrity pathway(s) were also down-regulated in the chs2∆ strain. Genes coding for proteins involved in autophagy were coordinately upregulated only in the chs2∆ strain yet an ATG9 genetic knockout that completely blocks autophagy was viable in chs2∆ and myo1∆ genetic backgrounds.. However, the chs2∆ strain was significantly more susceptible to lysis by B-1,3-glucanase than myo1∆ and fks1 control strains. We interpret this result to indicate that these two cytokinesis mutant strains possess different cell wall properties. This interpretation was further supported by the observation that Slt2p hyperphosphorylation was detected in the chs2∆ strain yet expression of SLT2 was not required for cell viability. We conclude that in contrast to myo1∆ strains, chs2∆ strains do not activate the cell integrity pathway.
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