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Quisel, John D., William F. Burkholder, and Alan D. Grossman. "In Vivo Effects of Sporulation Kinases on Mutant Spo0A Proteins in Bacillus subtilis." Journal of Bacteriology 183, no. 22 (November 15, 2001): 6573–78. http://dx.doi.org/10.1128/jb.183.22.6573-6578.2001.
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ABSTRACT The phosphorylated form of the response regulator Spo0A (Spo0A∼P) is required for the initiation of sporulation in Bacillus subtilis. Phosphate is transferred to Spo0A from at least four histidine kinases (KinA, KinB, KinC, and KinD) by a phosphotransfer pathway composed of Spo0F and Spo0B. Several mutations inspo0A allow initiation of sporulation in the absence ofspo0F and spo0B, but the mechanisms by which these mutations allow bypass of spo0F andspo0B are not fully understood. We measured the ability of KinA, KinB, and KinC to activate sporulation of fivespo0A mutants in the absence of Spo0F and Spo0B. We also determined the effect of Spo0E, a Spo0A∼P-specific phosphatase, on sporulation of strains containing the spo0A mutations. Our results indicate that several of the mutations relax the specificity of Spo0A, allowing Spo0A to obtain phosphate from a broader group of phosphodonors. In the course of these experiments, we observed medium-dependent effects on the sporulation of different mutants. This led us to identify a small molecule, acetoin, that can stimulate sporulation of some spo0A mutants.
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Underwood, Sarah, Shuang Guan, Vinod Vijayasubhash, Simon D. Baines, Luke Graham, Richard J. Lewis, Mark H. Wilcox, and Keith Stephenson. "Characterization of the Sporulation Initiation Pathway of Clostridium difficile and Its Role in Toxin Production." Journal of Bacteriology 191, no. 23 (September 25, 2009): 7296–305. http://dx.doi.org/10.1128/jb.00882-09.
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ABSTRACT Clostridium difficile is responsible for significant mortality and morbidity in the hospitalized elderly. C. difficile spores are infectious and are a major factor contributing to nosocomial transmission. The Spo0A response regulator is the master regulator for sporulation initiation and can influence many other cellular processes. Using the ClosTron gene knockout system, we inactivated genes encoding Spo0A and a putative sporulation-associated sensor histidine kinase in C. difficile. Inactivation of spo0A resulted in an asporogeneous phenotype, whereas inactivation of the kinase reduced C. difficle sporulation capacity by 3.5-fold, suggesting that this kinase also has a role in sporulation initiation. Furthermore, inactivation of either spo0A or the kinase resulted in a marked defect in C. difficile toxin production. Therefore, Spo0A and the signaling pathway that modulates its activity appear to be involved in regulation of toxin synthesis in C. difficile. In addition, Spo0A was directly phosphorylated by a putative sporulation-associated kinase, supporting the hypothesis that sporulation initiation in C. difficile is controlled by a two-component signal transduction system rather than a multicomponent phosphorelay. The implications of these findings for C. difficile sporulation, virulence, and transmission are discussed.
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Brunsing, Ryan L., Chandra La Clair, Sharon Tang, Christina Chiang, Lynn E. Hancock, Marta Perego, and James A. Hoch. "Characterization of Sporulation Histidine Kinases of Bacillus anthracis." Journal of Bacteriology 187, no. 20 (October 15, 2005): 6972–81. http://dx.doi.org/10.1128/jb.187.20.6972-6981.2005.
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ABSTRACT The initiation of sporulation in Bacillus species is regulated by the phosphorelay signal transduction pathway, which is activated by several histidine sensor kinases in response to cellular and metabolic signals. Comparison of the protein components of the phosphorelay between Bacillus subtilis and Bacillus anthracis revealed high homology in the phosphorelay orthologs of Spo0F, Spo0B, and Spo0A. The sensor domains of sensor histidine kinases are poorly conserved between species, making ortholog recognition tenuous. Putative sporulation sensor histidine kinases of B. anthracis were identified by homology to the HisKA domain of B. subtilis sporulation sensor histidine kinases, which interacts with Spo0F. Nine possible kinases were uncovered, and their genes were assayed for complementation of kinase mutants of B. subtilis, for ability to drive lacZ expression in B. subtilis and B. anthracis, and for the effect of deletion of each on the sporulation of B. anthracis. Five of the nine sensor histidine kinases were inferred to be capable of inducing sporulation in B. anthracis. Four of the sensor kinases could not be shown to induce sporulation; however, the genes for two of these were frameshifted in all B. anthracis strains and one of these was also frameshifted in the pathogenic pXO1-bearing Bacillus cereus strain G9241. It is proposed that acquisition of plasmid pXO1 and pathogenicity may require a dampening of sporulation regulation by mutational selection of sporulation sensor histidine kinase defects. The sporulation of B. anthracis ex vivo appears to result from any one or a combination of the sporulation sensor histidine kinases remaining.
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Bongiorni, Cristina, Ricarda Stoessel, and Marta Perego. "Negative Regulation of Bacillus anthracis Sporulation by the Spo0E Family of Phosphatases." Journal of Bacteriology 189, no. 7 (January 26, 2007): 2637–45. http://dx.doi.org/10.1128/jb.01798-06.
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ABSTRACT The initiation of sporulation in Bacillus species is controlled by the phosphorelay signal transduction system. Multiple regulatory elements act on the phosphorelay to modulate the level of protein phosphorylation in response to cellular, environmental, and metabolic signals. In Bacillus anthracis nine possible histidine sensor kinases can positively activate the system, while two response regulator aspartyl phosphate phosphatases of the Rap family negatively impact the pathway by dephosphorylating the Spo0F intermediate response regulator. In this study, we have characterized the B. anthracis members of the Spo0E family of phosphatases that specifically dephosphorylate the Spo0A response regulator of the phosphorelay and master regulator of sporulation. The products of four genes were able to promote the dephosphorylation of Spo0A∼P in vitro. The overexpression of two of these B. anthracis Spo0E-like proteins from a multicopy vector consistently resulted in a sporulation-deficient phenotype. A third gene was found to be not transcribed in vivo. A fourth gene encoded a prematurely truncated protein due to a base pair deletion that nevertheless was subject to translational frameshift repair in an Escherichia coli protein expression system. A fifth Spo0E-like protein has been structurally and functionally characterized as a phosphatase of Spo0A∼P by R. N. Grenha et al. (J. Biol. Chem. 281:37993-38003, 2006). We propose that these proteins may contribute to maintain B. anthracis in the transition phase of growth during an active infection and therefore contribute to the virulence of this organism.
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Bongiorni, Cristina, Ricarda Stoessel, Dorinda Shoemaker, and Marta Perego. "Rap Phosphatase of Virulence Plasmid pXO1 Inhibits Bacillus anthracis Sporulation." Journal of Bacteriology 188, no. 2 (January 15, 2006): 487–98. http://dx.doi.org/10.1128/jb.188.2.487-498.2006.
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ABSTRACT This study shows that the Bacillus anthracis pXO1 virulence plasmid carries a Rap-Phr system, BXA0205, which regulates sporulation initiation in this organism. The BXA0205Rap protein was shown to dephosphorylate the Spo0F response regulator intermediate of the phosphorelay signal transduction system that regulates the initiation of the developmental pathway in response to environmental, metabolic, and cell cycle signals. The activity of the Rap protein was shown to be inhibited by the carboxy-terminal pentapeptide generated through an export-import processing pathway from the associated BXA0205Phr protein. Deregulation of the Rap activity by either overexpression or lack of the Phr pentapeptide resulted in severe inhibition of sporulation. Five additional Rap-Phr encoding systems were identified on the chromosome of B. anthracis, one of which, BA3790-3791, also affected sporulation initiation. The results suggest that the plasmid-borne Rap-Phr system may provide a selective advantage to the virulence of B. anthracis.
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Gottig, Natalia, María Eugenia Pedrido, Marcelo Méndez, Esteban Lombardía, Adrián Rovetto, Valeria Philippe, Lelia Orsaria, and Roberto Grau. "The Bacillus subtilis SinR and RapA Developmental Regulators Are Responsible for Inhibition of Spore Development by Alcohol." Journal of Bacteriology 187, no. 8 (April 15, 2005): 2662–72. http://dx.doi.org/10.1128/jb.187.8.2662-2672.2005.
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ABSTRACT Even though there is a large body of information concerning the harmful effects of alcohol on different organisms, the mechanism(s) that affects developmental programs, at a single-cell level, has not been clearly identified. In this respect, the spore-forming bacterium Bacillus subtilis constitutes an excellent model to study universal questions of cell fate, cell differentiation, and morphogenesis. Here, we demonstrate that treatment with subinhibitory concentrations of alcohol that did not affect vegetative growth inhibited the initiation of spore development through a selective blockage of key developmental genes under the control of the master transcription factor Spo0A∼P. Isopropyl-β-d-thiogalactopyranoside-directed expression of a phosphorylation-independent form of Spo0A (Sad67) and the use of an in vivo mini-Tn10 insertional library permitted the identification of the developmental SinR repressor and RapA phosphatase as the effectors that mediated the inhibitory effect of alcohol on spore morphogenesis. A double rapA sinR mutant strain was completely resistant to the inhibitory effects of different-C-length alcohols on sporulation, indicating that the two cell fate determinants were the main or unique regulators responsible for the spo0 phenotype of wild-type cells in the presence of alcohol. Furthermore, treatment with alcohol produced a significant induction of rapA and sinR, while the stationary-phase induction of sinI, which codes for a SinR inhibitor, was completely turned off by alcohol. As a result, a dramatic repression of spo0A and the genes under its control occurred soon after alcohol addition, inhibiting the onset of sporulation and permitting the evaluation of alternative pathways required for cellular survival.
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Devi, Seram Nganbiton, Brittany Kiehler, Lindsey Haggett, and Masaya Fujita. "Evidence that Autophosphorylation of the Major Sporulation Kinase in Bacillus subtilis Is Able To Occur in trans." Journal of Bacteriology 197, no. 16 (June 8, 2015): 2675–84. http://dx.doi.org/10.1128/jb.00257-15.
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ABSTRACTEntry into sporulation inBacillus subtilisis governed by a multicomponent phosphorelay, a complex version of a two-component system which includes at least three histidine kinases (KinA to KinC), two phosphotransferases (Spo0F and Spo0B), and a response regulator (Spo0A). Among the three histidine kinases, KinA is known as the major sporulation kinase; it is autophosphorylated with ATP upon starvation and then transfers a phosphoryl group to the downstream components in a His-Asp-His-Asp signaling pathway. Our recent study demonstrated that KinA forms a homotetramer, not a dimer, mediated by the N-terminal domain, as a functional unit. Furthermore, when the N-terminal domain was overexpressed in the starving wild-type strain, sporulation was impaired. We hypothesized that this impairment of sporulation could be explained by the formation of a nonfunctional heterotetramer of KinA, resulting in the reduced level of phosphorylated Spo0A (Spo0A∼P), and thus, autophosphorylation of KinA could occur intrans. To test this hypothesis, we generated a series ofB. subtilisstrains expressing homo- or heterogeneous KinA protein complexes consisting of various combinations of the phosphoryl-accepting histidine point mutant protein and the catalytic ATP-binding domain point mutant protein. We found that the ATP-binding-deficient protein was phosphorylated when the phosphorylation-deficient protein was present in a 1:1 stoichiometry in the tetramer complex, while each of the mutant homocomplexes was not phosphorylated. These results suggest that ATP initially binds to one protomer within the tetramer complex and then the γ-phosphoryl group is transmitted to another in atransfashion. We further found that the sporulation defect of each of the mutant proteins is complemented when the proteins are coexpressedin vivo. Taken together, thesein vitroandin vivoresults reinforce the evidence that KinA autophosphorylation is able to occur in atransfashion.IMPORTANCEAutophosphorylation of histidine kinases is known to occur by either thecis(one subunit of kinase phosphorylating itself within the multimer) or thetrans(one subunit of the multimer phosphorylates the other subunit) mechanism. The present study provided directin vivoandin vitroevidence that autophosphorylation of the major sporulation histidine kinase (KinA) is able to occur intranswithin the homotetramer complex. While the physiological and mechanistic significance of thetransautophosphorylation reaction remains obscure, understanding the detailed reaction mechanism of the sporulation kinase is the first step toward gaining insight into the molecular mechanisms of the initiation of sporulation, which is believed to be triggered by unknown factors produced under conditions of nutrient depletion.
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de Jong, Imke G., Jan-Willem Veening, and Oscar P. Kuipers. "Heterochronic Phosphorelay Gene Expression as a Source of Heterogeneity in Bacillus subtilis Spore Formation." Journal of Bacteriology 192, no. 8 (February 12, 2010): 2053–67. http://dx.doi.org/10.1128/jb.01484-09.
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ABSTRACT In response to limiting nutrient sources and cell density signals, Bacillus subtilis can differentiate and form highly resistant endospores. Initiation of spore development is governed by the master regulator Spo0A, which is activated by phosphorylation via a multicomponent phosphorelay. Interestingly, only part of a clonal population will enter this developmental pathway, a phenomenon known as sporulation bistability or sporulation heterogeneity. How sporulation heterogeneity is established is largely unknown. To investigate the origins of sporulation heterogeneity, we constructed promoter-green fluorescent protein (GFP) fusions to the main phosphorelay genes and perturbed their expression levels. Using time-lapse fluorescence microscopy and flow cytometry, we showed that expression of the phosphorelay genes is distributed in a unimodal manner. However, single-cell trajectories revealed that phosphorelay gene expression is highly dynamic or “heterochronic” between individual cells and that stochasticity of phosphorelay gene transcription might be an important regulatory mechanism for sporulation heterogeneity. Furthermore, we showed that artificial induction or depletion of the phosphorelay phosphate flow results in loss of sporulation heterogeneity. Our data suggest that sporulation heterogeneity originates from highly dynamic and variable gene activity of the phosphorelay components, resulting in large cell-to-cell variability with regard to phosphate input into the system. These transcriptional and posttranslational differences in phosphorelay activity appear to be sufficient to generate a heterogeneous sporulation signal without the need of the positive-feedback loop established by the sigma factor SigH.
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Stephenson, Sophie, Christian Mueller, Min Jiang, and Marta Perego. "Molecular Analysis of Phr Peptide Processing in Bacillus subtilis." Journal of Bacteriology 185, no. 16 (August 15, 2003): 4861–71. http://dx.doi.org/10.1128/jb.185.16.4861-4871.2003.
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ABSTRACT In Bacillus subtilis, an export-import pathway regulates production of the Phr pentapeptide inhibitors of Rap proteins. Processing of the Phr precursor proteins into the active pentapeptide form is a key event in the initiation of sporulation and competence development. The PhrA (ARNQT) and PhrE (SRNVT) peptides inhibit the RapA and RapE phosphatases, respectively, whose activity is directed toward the Spo0F∼P intermediate response regulator of the sporulation phosphorelay. The PhrC (ERGMT) peptide inhibits the RapC protein acting on the ComA response regulator for competence with regard to DNA transformation. The structural organization of PhrA, PhrE, and PhrC suggested a role for type I signal peptidases in the processing of the Phr preinhibitor, encoded by the phr genes, into the proinhibitor form. The proinhibitor was then postulated to be cleaved to the active pentapeptide inhibitor by an additional enzyme. In this report, we provide evidence that Phr preinhibitor proteins are subject to only one processing event at the peptide bond on the amino-terminal end of the pentapeptide. This processing event is most likely independent of type I signal peptidase activity. In vivo and in vitro analyses indicate that none of the five signal peptidases of B. subtilis (SipS, SipT, SipU, SipV, and SipW) are indispensable for Phr processing. However, we show that SipV and SipT have a previously undescribed role in sporulation, competence, and cell growth.
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Chibazakura, T., F. Kawamura, K. Asai, and H. Takahashi. "Effects of spo0 mutations on spo0A promoter switching at the initiation of sporulation in Bacillus subtilis." Journal of bacteriology 177, no. 15 (1995): 4520–23. http://dx.doi.org/10.1128/jb.177.15.4520-4523.1995.
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Hoch, James A. "The phosphorelay signal transduction pathway in the initiation ofBacillus subtilis sporulation." Journal of Cellular Biochemistry 51, no. 1 (January 1993): 55–61. http://dx.doi.org/10.1002/jcb.240510111.
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Davidson, Philip, Rory Eutsey, Brendan Redler, N. Luisa Hiller, Michael T. Laub, and Dannie Durand. "Flexibility and constraint: Evolutionary remodeling of the sporulation initiation pathway in Firmicutes." PLOS Genetics 14, no. 9 (September 13, 2018): e1007470. http://dx.doi.org/10.1371/journal.pgen.1007470.
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Adams, Thomas H., Jenny K. Wieser, and Jae-Hyuk Yu. "Asexual Sporulation in Aspergillus nidulans." Microbiology and Molecular Biology Reviews 62, no. 1 (March 1, 1998): 35–54. http://dx.doi.org/10.1128/mmbr.62.1.35-54.1998.
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SUMMARY The formation of mitotically derived spores, called conidia, is a common reproductive mode in filamentous fungi, particularly among the large fungal class Ascomycetes. Asexual sporulation strategies are nearly as varied as fungal species; however, the formation of conidiophores, specialized multicellular reproductive structures, by the filamentous fungus Aspergillus nidulans has emerged as the leading model for understanding the mechanisms that control fungal sporulation. Initiation of A. nidulans conidipohore formation can occur either as a programmed event in the life cycle in response to intrinsic signals or to environmental stresses such as nutrient deprivation. In either case, a development-specific set of transcription factors is activated and these control the expression of each other as well as genes required for conidiophore morphogenesis. Recent progress has identified many of the earliest-acting genes needed for initiating conidiophore development and shown that there are at least two antagonistic signaling pathways that control this process. One pathway is modulated by a heterotrimeric G protein that when activated stimulates growth and represses both asexual and sexual sporulation as well as production of the toxic secondary metabolite, sterigmatocystin. The second pathway apparently requires an extracellular signal to induce sporulation-specific events and to direct the inactivation of the first pathway, removing developmental repression. A working model is presented in which the regulatory interactions between these two pathways during the fungal life cycle determine whether cells grow or develop.
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Lee, R. H., and S. M. Honigberg. "Nutritional regulation of late meiotic events in Saccharomyces cerevisiae through a pathway distinct from initiation." Molecular and Cellular Biology 16, no. 6 (June 1996): 3222–32. http://dx.doi.org/10.1128/mcb.16.6.3222.
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The IME1 gene is essential for initiation of meiosis in the yeast Saccharomyces cerevisiae, although it is not required for growth. Here we report that in stationary-phase cultures containing low concentration of glucose, cells overexpressing IME1 undergo the early meiotic events, including DNA replication, commitment to recombination, and synaptonemal complex formation and dissolution. In contrast, later meiotic events, such as chromosome segregation, commitment to meiosis, and spore formation, do not occur. Thus, nutrients can repress the late stages of meiosis independently of their block of initiation. Cells arrested at this midpoint in meiosis are relatively stable and can resume meiotic differentiation if transferred to sporulation conditions. Resumption of meiosis does not require repression of IME1 expression, since IME1 RNA levels stay high after transfer of the arrested cells to sporulation medium. These results suggest that meiosis in S. cerevisiae is a paradigm of a differentiation pathway regulated by signal transduction at both early and late stages.
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Imada, Kazuki, and Taro Nakamura. "The exocytic Rabs Ypt3 and Ypt2 regulate the early step of biogenesis of the spore plasma membrane in fission yeast." Molecular Biology of the Cell 27, no. 21 (November 2016): 3317–28. http://dx.doi.org/10.1091/mbc.e16-03-0162.
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During fission yeast sporulation, a membrane compartment called the forespore membrane (FSM) is newly formed on the spindle pole body (SPB). The FSM expands by membrane vesicle fusion, encapsulates the daughter nucleus resulting from meiosis, and eventually matures into the plasma membrane of the spore. Although many of the genes involved in FSM formation have been identified, its molecular mechanism is not fully understood. Here a genetic screen for sporulation-deficient mutations identified Ypt3, a Rab-family small GTPase known to function in the exocytic pathway. The ypt3-ki8 mutant showed defects in both the initiation of FSM biogenesis and FSM expansion. We also show that a mutation in Ypt2, another Rab protein that may function in the same pathway as Ypt3, compromises the initiation of FSM formation. As meiosis proceeds, both GFP-Ypt3 and GFP-Ypt2 are observed at the SPB and then relocalize to the FSM. Their localizations at the SPB precede FSM formation and depend on the meiotic SPB component Spo13, a putative GDP/GTP exchange factor for Ypt2. Given that Spo13 is essential for initiating FSM formation, these results suggest that two exocytic Rabs, Ypt3 and Ypt2, regulate the initiation of FSM formation on the SPB in concert with Spo13.
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Benni, Mei Li, and Lenore Neigeborn. "Identification of a New Class of Negartive Regulators Affecting Sporulation-Specific Gene Expression in Yeast." Genetics 147, no. 3 (November 1, 1997): 1351–66. http://dx.doi.org/10.1093/genetics/147.3.1351.
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We characterized two yeast loci, MDS3 and PMD1, that negatively regulate sporulation. Initiation of sporulation is mediated by the meiotic activator IME1, which relies on MCK1 for maximal expression. We isolated the MDS3-1 allele (encoding a truncated form of Mds3p) as a suppressor that restores IME1 expression in mck1 mutants. mds3 null mutations confer similar suppression phenotypes as MDS3-1, indicating that Mds3p is a negative regulator of sporulation and the MDS3-1 allele confers a dominant-negative phenotype. PMD1 is predicted to encode a protein sharing significant similarity with Mds3p. mds3 pmd1 double mutants are better suppressors of mck1 than is either single mutant, indicating that Mds3p and Pmd1p function synergistically. Northern blot analysis revealed that suppression is due to increased IME1 transcript accumulation. The roles of Mds3p and Pmd1p are not restricted to the MCK1 pathway because mds3 pmd1 mutations also suppress IME1 expression defects associated with MCK1-independent sporulation mutants. Furthermore, mds3 pmdl mutants express significant levels of IME1 even in vegetative cells and this unscheduled expression results in premature sporulation. These phenotypes, and interactions with RAS2-Val19 suggest that unscheduled derepression of IME1 is probably due to a defect in recognition of nutritional status.
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Simchen, Giora, and Yona Kassir. "Genetic regulation of differentiation towards meiosis in the yeast Saccharomyces cerevisiae." Genome 31, no. 1 (January 1, 1989): 95–99. http://dx.doi.org/10.1139/g89-018.
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Normally, meiosis and sporulation in Saccharomyces cerevisiae occur only in diploid strains and only when the cells are exposed to starvation conditions. Diploidy is determined by the mating-type system (the genes MAT, RME1, IME1), whereas the starvation signal is transmitted through the adenylate cyclase – protein kinase pathway (the genes CDC25, RAS2, CDC35 (CYR1), BCY1, TPK1, TPK2, TPK3). The two regulatory pathways converge at the gene IME1, which is a positive regulator of meiosis and whose early expression in sporulating cells correlates with the initiation of meiosis. Sites upstream (5′) of IME1 appear to mediate in the repression of the gene by repressors originating from both the mating-type and the cyclase – kinase pathways.Key words: sporulation, mating type, diploidy, adenylate cyclase, cAMP, protein kinase.
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Fukushima, Sanae, Mika Yoshimura, Taku Chibazakura, Tsutomu Sato, and Hirofumi Yoshikawa. "The putative ABC transporter YheH/YheI is involved in the signalling pathway that activates KinA during sporulation initiation." FEMS Microbiology Letters 256, no. 1 (March 2006): 90–97. http://dx.doi.org/10.1111/j.1574-6968.2006.00104.x.
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Honigberg, Saul M., and Rita H. Lee. "Snf1 Kinase Connects Nutritional Pathways Controlling Meiosis in Saccharomyces cerevisiae." Molecular and Cellular Biology 18, no. 8 (August 1, 1998): 4548–55. http://dx.doi.org/10.1128/mcb.18.8.4548.
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ABSTRACT Glucose inhibits meiosis in Saccharomyces cerevisiae at three different steps (IME1 transcription, IME2transcription, and entry into late stages of meiosis). Because many of the regulatory effects of glucose in yeast are mediated through the inhibition of Snf1 kinase, a component of the glucose repression pathway, we determined the role of SNF1 in regulating meiosis. Deleting SNF1 repressed meiosis at the same three steps that were inhibited by glucose, suggesting that glucose blocks meiosis by inhibiting Snf1. For example, the snf1Δ mutant completely failed to induce IME1 transcripts in sporulation medium. Furthermore, even when this block was bypassed by expression ofIME1 from a multicopy plasmid, IME2transcription and meiotic initiation occurred at only 10 to 20% of the levels seen in wild-type cells. The addition of glucose did not further inhibit IME2 transcription, suggesting that Snf1 is the primary mediator of glucose controls on IME2 expression. Finally, in snf1Δ cells in which both blocks on meiotic initiation were bypassed, early stages of meiosis (DNA replication and commitment to recombination) occurred, but later stages (chromosome segregation and spore formation) did not, suggesting that Snf1 controls later stages of meiosis independently from the two controls on meiotic initiation. Because Snf1 is known to activate the expression of genes required for acetate metabolism, it may also serve to connect glucose and acetate controls on meiotic differentiation.
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Li, Wencheng, Xin Ying, Yuzheng Guo, Zhen Yu, Xiufen Zhou, Zixin Deng, Helen Kieser, Keith F. Chater, and Meifeng Tao. "Identification of a Gene Negatively Affecting Antibiotic Production and Morphological Differentiation in Streptomyces coelicolor A3(2)." Journal of Bacteriology 188, no. 24 (October 13, 2006): 8368–75. http://dx.doi.org/10.1128/jb.00933-06.
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ABSTRACT SC7A1 is a cosmid with an insert of chromosomal DNA from Streptomyces coelicolor A3(2). Its insertion into the chromosome of S. coelicolor strains caused a duplication of a segment of ca. 40 kb and delayed actinorhodin antibiotic production and sporulation, implying that SC7A1 carried a gene negatively affecting these processes. The subcloning of SC7A1 insert DNA resulted in the identification of the open reading frame SCO5582 as nsdA, a gene n egatively affecting S treptomyces d ifferentiation. The disruption of chromosomal nsdA caused the overproduction of spores and of three of four known S. coelicolor antibiotics of quite different chemical types. In at least one case (that of actinorhodin), this was correlated with premature expression of a pathway-specific regulatory gene (actII-orf4), implying that nsdA in the wild-type strain indirectly repressed the expression of the actinorhodin biosynthesis cluster. nsdA expression was up-regulated upon aerial mycelium initiation and was strongest in the aerial mycelium. NsdA has DUF921, a Streptomyces protein domain of unknown function and a conserved SXR site. A site-directed mutation (S458A) in this site in NsdA abolished its function. Blast searching showed that NsdA homologues are present in some Streptomyces genomes. Outside of streptomycetes, NsdA-like proteins have been found in several actinomycetes. The disruption of the nsdA-like gene SCO4114 had no obvious phenotypic effects on S. coelicolor. The nsdA orthologue SAV2652 in S. avermitilis could complement the S. coelicolor nsdA-null mutant phenotype.
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Zhou, Xiaogang, Likun Zheng, Luyu Guan, Jing Ye, Aleksandra Virag, Steven D. Harris, and Ling Lu. "The Scaffold Proteins Paxillin B and α-Actinin Regulate Septation in Aspergillus nidulans via Control of Actin Ring Contraction." Genetics 215, no. 2 (April 21, 2020): 449–61. http://dx.doi.org/10.1534/genetics.120.303234.
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Cytokinesis, as the final step of cell division, plays an important role in fungal growth and proliferation. In the filamentous fungus Aspergillus nidulans, defective cytokinesis is able to induce abnormal multinuclear or nonnucleated cells and then result in reduced hyphal growth and abolished sporulation. Previous studies have reported that a conserved contractile actin ring (CAR) protein complex and the septation initiation network (SIN) signaling kinase cascade are required for cytokinesis and septation; however, little is known about the role(s) of scaffold proteins involved in these two important cellular processes. In this study, we show that a septum-localized scaffold protein paxillin B (PaxB) is essential for cytokinesis/septation in A. nidulans. The septation defects observed in a paxB deletion strain resemble those caused by the absence of another identified scaffold protein, α-actinin (AcnA). Deletion of α-actinin (AcnA) leads to undetectable PaxB at the septation site, whereas deletion of paxB does not affect the localization of α-actinin at septa. However, deletion of either α-actinin (acnA) or paxB causes the actin ring to disappear at septation sites during cytokinesis. Notably, overexpression of α-actinin acnA partially rescues the septum defects of the paxB mutant but not vice versa, suggesting AcnA may play a dominant role over that of PaxB for cytokinesis and septation. In addition, PaxB and α-actinin affect the septal dynamic localization of MobA, a conserved component of the SIN pathway, suggesting they may affect the SIN protein complex function at septa. Protein pull-down assays combined with liquid chromatography–mass spectrometry identification indicate that α-actinin AcnA and PaxB likely do not directly interact, but presumably belong to an actin cytoskeleton protein network that is required for the assembly and contraction of the CAR. Taken together, findings in this study provide novel insights into the roles of conserved scaffold proteins during fungal septation in A. nidulans.
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Martinez-Amador, Paola, Nori Castañeda, Antonio Loza, Lizeth Soto, Enrique Merino, and Rosa Maria Gutierrez-Rios. "Prediction of protein architectures involved in the signaling-pathway initiating sporulation in Firmicutes." BMC Research Notes 12, no. 1 (October 23, 2019). http://dx.doi.org/10.1186/s13104-019-4712-3.
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Abstract Objectives Like many other proteins, those belonging to the signal transduction cascade initiating sporulation (Spo0 pathway) have conserved protein domains (Capra and Laub in Annu Rev Microbiol 66:325–47, 2012). Improvements in bioinformatics applications to discover proteins involved in the initiation of the sporulating cascade in newly sequenced genomes is an important task that requires rigorous comparative genomic methods and manual curation to identify endospore-forming bacteria. This note aims to present a collection of predicted proteins involved in the Spo0 pathway found in the proteomes of fully sequenced and manually curated endospore-forming Firmicutes species. This collection may serve as a guide to conduct future experiments in endospore formers in genomic and metagenomic projects. Data description Similar to the report of Davidson et al. (PLoS Genet 14:1–33, 2018), we used Pfam profiles (El-Gebali et al. in Nucleic Acids Res 47:D427–32, 2019) defining each protein and the genomic context surrounding the query gene to predict probable orthologs of the Spo0 pathway in Firmicutes. We present in this note a collection of 325 Firmicutes species organized by phylogenetic class and classified as spore formers, non-spore formers or unknown spore phenotype based on published literature, for which we predicted probable orthologs defining the signal transduction pathway initiating sporulation.