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Cell dispersal by localized degradation of a chemoattractant. Proc Natl Acad Sci U S A 2021; 118:2008126118. [PMID: 33526658 DOI: 10.1073/pnas.2008126118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chemotaxis, the guided motion of cells by chemical gradients, plays a crucial role in many biological processes. In the social amoeba Dictyostelium discoideum, chemotaxis is critical for the formation of cell aggregates during starvation. The cells in these aggregates generate a pulse of the chemoattractant, cyclic adenosine 3',5'-monophosphate (cAMP), every 6 min to 10 min, resulting in surrounding cells moving toward the aggregate. In addition to periodic pulses of cAMP, the cells also secrete phosphodiesterase (PDE), which degrades cAMP and prevents the accumulation of the chemoattractant. Here we show that small aggregates of Dictyostelium can disperse, with cells moving away from instead of toward the aggregate. This surprising behavior often exhibited oscillatory cycles of motion toward and away from the aggregate. Furthermore, the onset of outward cell motion was associated with a doubling of the cAMP signaling period. Computational modeling suggests that this dispersal arises from a competition between secreted cAMP and PDE, creating a cAMP gradient that is directed away from the aggregate, resulting in outward cell motion. The model was able to predict the effect of PDE inhibition as well as global addition of exogenous PDE, and these predictions were subsequently verified in experiments. These results suggest that localized degradation of a chemoattractant is a mechanism for morphogenesis.
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Schaap P. From environmental sensing to developmental control: cognitive evolution in dictyostelid social amoebas. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190756. [PMID: 33487113 PMCID: PMC7934950 DOI: 10.1098/rstb.2019.0756] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Dictyostelid social amoebas respond to starvation by self-organizing into multicellular slugs that migrate towards light to construct spore-bearing structures. These behaviours depend on excitable networks that enable amoebas to produce propagating waves of the chemoattractant cAMP, and to respond by directional movement. cAMP additionally regulates cell differentiation throughout development, with differentiation and cell movement being coordinated by interaction of the stalk inducer c-di-GMP with the adenylate cyclase that generates cAMP oscillations. Evolutionary studies indicate how the manifold roles of cAMP in multicellular development evolved from a role as intermediate for starvation-induced encystation in the unicellular ancestor. A merger of this stress response with the chemotaxis excitable networks yielded the developmental complexity and cognitive capabilities of extant Dictyostelia. This article is part of the theme issue ‘Basal cognition: conceptual tools and the view from the single cell’.
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Affiliation(s)
- Pauline Schaap
- School of Life Sciences, University of Dundee, Dundee DD15EH, UK
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Kawabe Y, Du Q, Schilde C, Schaap P. Evolution of multicellularity in Dictyostelia. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2020; 63:359-369. [PMID: 31840775 PMCID: PMC6978153 DOI: 10.1387/ijdb.190108ps] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The well-orchestrated multicellular life cycle of Dictyostelium discoideum has fascinated biologists for over a century. Self-organisation of its amoebas into aggregates, migrating slugs and fruiting structures by pulsatile cAMP signalling and their ability to follow separate differentiation pathways in well-regulated proportions continue to be topics under investigation. A striking aspect of D. discoideum development is the recurrent use of cAMP as chemoattractant, differentiation inducing signal and second messenger for other signals that control the developmental programme. D. discoideum is one of >150 species of Dictyostelia and aggregative life styles similar to those of Dictyostelia evolved many times in eukaryotes. Here we review experimental studies investigating how phenotypic complexity and cAMP signalling co-evolved in Dictyostelia. In addition, we summarize comparative genomic studies of multicellular Dictyostelia and unicellular Amoebozoa aimed to identify evolutionary conservation and change in all genes known to be essential for D. discoideum development.
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Ito T, Hamauchi N, Hagi T, Morohashi N, Hemmi H, Sato YG, Saito T, Yoshimura T. D-Serine Metabolism and Its Importance in Development of Dictyostelium discoideum. Front Microbiol 2018; 9:784. [PMID: 29740415 PMCID: PMC5928759 DOI: 10.3389/fmicb.2018.00784] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 04/06/2018] [Indexed: 11/13/2022] Open
Abstract
In mammals, D-Ser is synthesized by serine racemase (SR) and degraded by D-amino acid oxidase (DAO). D-Ser acts as an endogenous ligand for N-methyl-D-aspartate (NMDA)- and δ2 glutamate receptors, and is involved in brain functions such as learning and memory. Although SR homologs are highly conserved in eukaryotes, little is known about the significance of D-Ser in non-mammals. In contrast to mammals, the slime mold Dictyostelium discoideum genome encodes SR, DAO, and additionally D-Ser specific degradation enzyme D-Ser dehydratase (DSD), but not NMDA- and δ2 glutamate receptors. Here, we studied the significances of D-Ser and DSD in D. discoideum. Enzymatic assays demonstrated that DSD is 460- and 1,700-fold more active than DAO and SR, respectively, in degrading D-Ser. Moreover, in dsd-null cells D-Ser degradation activity is completely abolished. In fact, while in wild-type D. discoideum intracellular D-Ser levels were considerably low, dsd-null cells accumulated D-Ser. These results indicated that DSD but not DAO is the primary enzyme responsible for D-Ser decomposition in D. discoideum. We found that dsd-null cells exhibit delay in development and arrest at the early culmination stage. The efficiency of spore formation was considerably reduced in the mutant cells. These phenotypes were further pronounced by exogenous D-Ser but rescued by plasmid-borne expression of dsd. qRT-PCR analysis demonstrated that mRNA expression of key genes in the cAMP signaling relay is perturbed in the dsd knockout. Our data indicate novel roles for D-Ser and/or DSD in the regulation of cAMP signaling in the development processes of D. discoideum.
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Affiliation(s)
- Tomokazu Ito
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Natsuki Hamauchi
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Taisuke Hagi
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Naoya Morohashi
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Hisashi Hemmi
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Yukie G Sato
- Department of Materials and Life Sciences, Sophia University, Tokyo, Japan
| | - Tamao Saito
- Department of Materials and Life Sciences, Sophia University, Tokyo, Japan
| | - Tohru Yoshimura
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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Rodriguez-Centeno J, Sastre L. Biological Activity of the Alternative Promoters of the Dictyostelium discoideum Adenylyl Cyclase A Gene. PLoS One 2016; 11:e0148533. [PMID: 26840347 PMCID: PMC4739590 DOI: 10.1371/journal.pone.0148533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 01/20/2016] [Indexed: 12/01/2022] Open
Abstract
Amoebae of the Dictyostelium discoideum species form multicellular fruiting bodies upon starvation. Cyclic adenosine monophosphate (cAMP) is used as intercellular signalling molecule in cell-aggregation, cell differentiation and morphogenesis. This molecule is synthesized by three adenylyl cyclases, one of which, ACA, is required for cell aggregation. The gene coding for ACA (acaA) is transcribed from three different promoters that are active at different developmental stages. Promoter 1 is active during cell-aggregation, promoters 2 and 3 are active in prespore and prestalk tip cells at subsequent developmental stages. The biological relevance of acaA expression from each of the promoters has been studied in this article. The acaA gene was expressed in acaA-mutant cells, that do not aggregate, under control of each of the three acaA promoters. acaA expression under promoter 1 control induced cell aggregation although subsequent development was delayed, very small fruiting bodies were formed and cell differentiation genes were expressed at very low levels. Promoter 2-driven acaA expression induced the formation of small aggregates and small fruiting bodies were formed at the same time as in wild-type strains and differentiation genes were also expressed at lower levels. Expression of acaA from promoter 3 induced aggregates and fruiting bodies formation and their size and the expression of differentiation genes were more similar to that of wild-type cells. Expression of acaA from promoters 1 and 2 in AX4 cells also produced smaller structures. In conclusion, the expression of acaA under control of the aggregation-specific Promoter 1 is able to induce cell aggregation in acaA-mutant strains. Expression from promoters 2 and 3 also recovered aggregation and development although promoter 3 induced a more complete recovery of fruiting body formation.
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Affiliation(s)
| | - Leandro Sastre
- Instituto de Investigaciones Biomédicas CSIC/UAM, C/Arturo Duperier, 4, 28029, Madrid, Spain
- CIBERER, Valencia, Spain
- * E-mail:
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Du Q, Kawabe Y, Schilde C, Chen ZH, Schaap P. The Evolution of Aggregative Multicellularity and Cell-Cell Communication in the Dictyostelia. J Mol Biol 2015; 427:3722-33. [PMID: 26284972 PMCID: PMC5055082 DOI: 10.1016/j.jmb.2015.08.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 06/30/2015] [Accepted: 08/03/2015] [Indexed: 10/30/2022]
Abstract
Aggregative multicellularity, resulting in formation of a spore-bearing fruiting body, evolved at least six times independently amongst both eukaryotes and prokaryotes. Amongst eukaryotes, this form of multicellularity is mainly studied in the social amoeba Dictyostelium discoideum. In this review, we summarise trends in the evolution of cell-type specialisation and behavioural complexity in the four major groups of Dictyostelia. We describe the cell-cell communication systems that control the developmental programme of D. discoideum, highlighting the central role of cAMP in the regulation of cell movement and cell differentiation. Comparative genomic studies showed that the proteins involved in cAMP signalling are deeply conserved across Dictyostelia and their unicellular amoebozoan ancestors. Comparative functional analysis revealed that cAMP signalling in D. discoideum originated from a second messenger role in amoebozoan encystation. We highlight some molecular changes in cAMP signalling genes that were responsible for the novel roles of cAMP in multicellular development.
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Affiliation(s)
- Qingyou Du
- College of Life Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom.
| | - Yoshinori Kawabe
- College of Life Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom.
| | - Christina Schilde
- College of Life Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom.
| | - Zhi-Hui Chen
- College of Life Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom.
| | - Pauline Schaap
- College of Life Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom.
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Narita TB, Chen ZH, Schaap P, Saito T. The hybrid type polyketide synthase SteelyA is required for cAMP signalling in early Dictyostelium development. PLoS One 2014; 9:e106634. [PMID: 25222736 PMCID: PMC4164351 DOI: 10.1371/journal.pone.0106634] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 08/08/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In our previous study we found that the expression of stlA showed peaks both in the early and last stages of development and that a product of SteelyA, 4-methyl-5-pentylbenzene-1,3-diol (MPBD), controlled Dictyostelium spore maturation during the latter. In this study we focused on the role of SteelyA in early stage development. PRINCIPAL FINDINGS Our stlA null mutant showed aggregation delay and abnormally small aggregation territories. Chemotaxis analysis revealed defective cAMP chemotaxis in the stlA null mutant. cAMP chemotaxis was restored by MPBD addition during early stage development. Assay for cAMP relay response revealed that the stlA null mutant had lower cAMP accumulation during aggregation, suggesting lower ACA activity than the wild type strain. Exogenous cAMP pulses rescued the aggregation defect of the stlA null strain in the absence of MPBD. Expression analysis of cAMP signalling genes revealed lower expression levels in the stlA null mutant during aggregation. CONCLUSION Our data indicate a regulatory function by SteelyA on cAMP signalling during aggregation and show that SteelyA is indispensable for full activation of ACA.
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Affiliation(s)
- Takaaki B. Narita
- Graduate School of Science and Technology, Sophia University, Tokyo, Japan
- Research Fellow of Japan Society for the Promotion of Science (DC2), Tokyo, Japan
| | - Zhi-hui Chen
- College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Pauline Schaap
- College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Tamao Saito
- Department of Materials and Life Sciences, Sophia University, Tokyo, Japan
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Masaki N, Fujimoto K, Honda-Kitahara M, Hada E, Sawai S. Robustness of self-organizing chemoattractant field arising from precise pulse induction of its breakdown enzyme: a single-cell level analysis of PDE expression in Dictyostelium. Biophys J 2013; 104:1191-202. [PMID: 23473502 DOI: 10.1016/j.bpj.2013.01.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 12/29/2012] [Accepted: 01/16/2013] [Indexed: 01/19/2023] Open
Abstract
The oscillation of chemoattractant cyclic AMP (cAMP) in Dictyostelium discoideum is a collective phenomenon that occurs when the basal level of extracellular cAMP exceeds a threshold and invokes cooperative mutual excitation of cAMP synthesis and secretion. For pulses to be relayed from cell to cell repetitively, secreted cAMP must be cleared and brought down to the subthreshold level. One of the main determinants of the oscillatory behavior is thus how much extracellular cAMP is degraded by extracellular phosphodiesterase (PDE). To date, the exact nature of PDE gene regulation remains elusive. Here, we performed live imaging analysis of mRNA transcripts for pdsA--the gene encoding extracellular PDE. Our analysis revealed that pdsA is upregulated during the rising phase of cAMP oscillations. Furthermore, by analyzing isolated cells, we show that expression of pdsA is strictly dependent on the presence of extracellular cAMP. pdsA is induced only at ∼1 nM extracellular cAMP, which is almost identical to the threshold concentration for the cAMP relay response. The observed precise regulation of PDE expression together with degradation of extracellular cAMP by PDE form a dual positive and negative feedback circuit, and model analysis shows that this sets the cAMP level near the threshold concentration for the cAMP relay response for a wide range of adenylyl cyclase activity. The overlap of the thresholds could allow oscillations of chemoattractant cAMP to self-organize at various starving conditions, making its development robust to fluctuations in its environment.
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Affiliation(s)
- Noritaka Masaki
- Exploratory Research for Advanced Technology (ERATO), Complex Systems Biology Project, Japan Science and Technology Agency (JST), Tokyo, Japan
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Galardi-Castilla M, Fernandez-Aguado I, Suarez T, Sastre L. Mef2A, a homologue of animal Mef2 transcription factors, regulates cell differentiation in Dictyostelium discoideum. BMC DEVELOPMENTAL BIOLOGY 2013; 13:12. [PMID: 23577638 PMCID: PMC3640940 DOI: 10.1186/1471-213x-13-12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 04/05/2013] [Indexed: 01/28/2023]
Abstract
Background Transcription factors from the MADS-box family play a relevant role in cell differentiation and development and include the animal SRF (serum response factor) and MEF2 (myocyte enhancer factor 2) proteins. The social amoeba Dictyostelium discoideum contains four genes coding for MADS-box transcription factors, two of these genes code for proteins that are more similar to SRF, and the other two code for proteins that are more similar to MEF2 animal factors. Results The biological function of one of the two genes that codes for MEF2-related proteins, a gene known as mef2A, is described in this article. This gene is expressed under the transcriptional control of two alternative promoters in growing cells, and its expression is induced during development in prespore cells. Mutant strains where the mef2A gene has been partially deleted were generated to study its biological function. The mutant strains showed reduced growth when feeding on bacteria and were able to develop and form fruiting bodies, but spore production was significantly reduced. A study of developmental markers showed that prespore cells differentiation was impaired in the mutant strains. When mutant and wild-type cells were set to develop in chimeras, mutant spores were underrepresented in the fruiting bodies. The mutant cells were also unable to form spores in vitro. In addition, mutant cells also showed a poor contribution to the formation of the tip-organizer and the upper region of slugs and culminant structures. In agreement with these observations, a comparison of the genes transcribed by mutant and wild-type strains during development indicated that prestalk gene expression was enhanced, while prespore gene expression decreased in the mef2A- strain. Conclusions Our data shows that mef2A plays a role in cell differentiation in D. discoideum and modulates the expression of prespore and prestalk genes.
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Affiliation(s)
- María Galardi-Castilla
- Instituto de Investigaciones Biomédicas de Madrid (Biomedical Research Institute of Madrid), CSIC/UAM, C/Arturo Duperier 4, 28029 Madrid, Spain
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Kawabe Y, Weening KE, Marquay-Markiewicz J, Schaap P. Evolution of self-organisation in Dictyostelia by adaptation of a non-selective phosphodiesterase and a matrix component for regulated cAMP degradation. Development 2012; 139:1336-45. [PMID: 22357931 PMCID: PMC3294436 DOI: 10.1242/dev.077099] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2012] [Indexed: 01/21/2023]
Abstract
Dictyostelium discoideum amoebas coordinate aggregation and morphogenesis by secreting cyclic adenosine monophosphate (cAMP) pulses that propagate as waves through fields of cells and multicellular structures. To retrace how this mechanism for self-organisation evolved, we studied the origin of the cAMP phosphodiesterase PdsA and its inhibitor PdiA, which are essential for cAMP wave propagation. D. discoideum and other species that use cAMP to aggregate reside in group 4 of the four major groups of Dictyostelia. We found that groups 1-3 express a non-specific, low affinity orthologue of PdsA, which gained cAMP selectivity and increased 200-fold in affinity in group 4. A low affinity group 3 PdsA only partially restored aggregation of a D. discoideum pdsA-null mutant, but was more effective at restoring fruiting body morphogenesis. Deletion of a group 2 PdsA gene resulted in disruption of fruiting body morphogenesis, but left aggregation unaffected. Together, these results show that groups 1-3 use a low affinity PdsA for morphogenesis that is neither suited nor required for aggregation. PdiA belongs to a family of matrix proteins that are present in all Dictyostelia and consist mainly of cysteine-rich repeats. However, in its current form with several extensively modified repeats, PdiA is only present in group 4. PdiA is essential for initiating spiral cAMP waves, which, by organising large territories, generate the large fruiting structures that characterise group 4. We conclude that efficient cAMP-mediated aggregation in group 4 evolved by recruitment and adaptation of a non-selective phosphodiesterase and a matrix component into a system for regulated cAMP degradation.
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Affiliation(s)
- Yoshinori Kawabe
- College of Life Sciences, University of Dundee, Dundee DD15EH, UK
| | | | | | - Pauline Schaap
- College of Life Sciences, University of Dundee, Dundee DD15EH, UK
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Schaap P. Evolution of developmental cyclic adenosine monophosphate signaling in the Dictyostelia from an amoebozoan stress response. Dev Growth Differ 2011; 53:452-62. [PMID: 21585352 PMCID: PMC3909795 DOI: 10.1111/j.1440-169x.2011.01263.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Dictyostelid social amoebas represent one of nature's several inventions of multicellularity. Though normally feeding as single cells, nutrient stress triggers the collection of amoebas into colonies that form delicately shaped fruiting structures in which the cells differentiate into spores and up to three cell types to support the spore mass. Cyclic adenosine monophosphate (cAMP) plays a very dominant role in controlling morphogenesis and cell differentiation in the model species Dictyostelium discoideum. As a secreted chemoattractant cAMP coordinates cell movement during aggregation and fruiting body morphogenesis. Secreted cAMP also controls gene expression at different developmental stages, while intracellular cAMP is extensively used to transduce the effect of other stimuli that control the developmental program. In this review, I present an overview of the different roles of cAMP in the model D. discoideum and I summarize studies aimed to resolve how these roles emerged during Dictyostelid evolution.
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Affiliation(s)
- Pauline Schaap
- College of Life Sciences, University of Dundee, MSI/WTB/JBC Complex, Dow Street, Dundee DD15EH, UK.
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Abstract
Dictyostelium discoideum belongs to a group of multicellular life forms that can also exist for long periods as single cells. This ability to shift between uni- and multicellularity makes the group ideal for studying the genetic changes that occurred at the crossroads between uni- and multicellular life. In this Primer, I discuss the mechanisms that control multicellular development in Dictyostelium discoideum and reconstruct how some of these mechanisms evolved from a stress response in the unicellular ancestor.
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Affiliation(s)
- Pauline Schaap
- College of Life Sciences, University of Dundee, Dundee, UK.
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Galardi-Castilla M, Garciandía A, Suarez T, Sastre L. The Dictyostelium discoideum acaA gene is transcribed from alternative promoters during aggregation and multicellular development. PLoS One 2010; 5:e13286. [PMID: 20949015 PMCID: PMC2952602 DOI: 10.1371/journal.pone.0013286] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 09/15/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Extracellular cAMP is a key extracellular signaling molecule that regulates aggregation, cell differentiation and morphogenesis during multi-cellular development of the social amoeba Dictyostelium discoideum. This molecule is produced by three different adenylyl cyclases, encoded by the genes acaA, acrA and acgA, expressed at different stages of development and in different structures. METHODOLOGY/PRINCIPAL FINDINGS This article describes the characterization of the promoter region of the acaA gene, showing that it is transcribed from three different alternative promoters. The distal promoter, promoter 1, is active during the aggregation process while the more proximal promoters are active in tip-organiser and posterior regions of the structures. A DNA fragment containing the three promoters drove expression to these same regions and similar results were obtained by in situ hybridization. Analyses of mRNA expression by quantitative RT-PCR with specific primers for each of the three transcripts also demonstrated their different temporal patterns of expression. CONCLUSIONS/SIGNIFICANCE The existence of an aggregation-specific promoter can be associated with the use of cAMP as chemo-attractant molecule, which is specific for some Dictyostelium species. Expression at late developmental stages indicates that adenylyl cyclase A might play a more important role in post-aggregative development than previously considered.
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Affiliation(s)
- Maria Galardi-Castilla
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cientificas/Universidad Autónoma de Madrid, Madrid, Spain
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Abstract
A fundamental goal of biology is to understand how novel phenotypes evolved through changes in existing genes. The Dictyostelia or social amoebas represent a simple form of multicellularity, where starving cells aggregate to build fruiting structures. This review summarizes efforts to provide a framework for investigating the genetic changes that generated novel morphologies in the Dictyostelia. The foundation is a recently constructed molecular phylogeny of the Dictyostelia, which was used to examine trends in the evolution of novel forms and in the divergence of genes that shape these forms. There is a major trend towards the formation of large unbranched fruiting bodies, which is correlated with the use of cyclic AMP (cAMP) as a secreted signal to coordinate cell aggregation. The role of cAMP in aggregation arose through co‐option of a pathway that originally acted to coordinate fruiting body formation. The genotypic changes that caused this innovation and the role of dynamic cAMP signaling in defining fruiting body size and pattern throughout social amoeba evolution are discussed. BioEssays 29:635–644, 2007. © 2007 Wiley Periodicals, Inc.
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Affiliation(s)
- Pauline Schaap
- College of Life Sciences, University of Dundee, MSI/WTB/JBC complex, Dow Street, Dundee DD1 5EH, UK.
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Bader S, Kortholt A, Van Haastert P. Seven Dictyostelium discoideum phosphodiesterases degrade three pools of cAMP and cGMP. Biochem J 2007; 402:153-61. [PMID: 17040207 PMCID: PMC1783984 DOI: 10.1042/bj20061153] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Dictyostelium discoideum genome uncovers seven cyclic nucleotide PDEs (phosphodiesterases), of which six have been characterized previously and the seventh is characterized in the present paper. Three enzymes belong to the ubiquitous class I PDEs, common in all eukaryotes, whereas four enzymes belong to the rare class II PDEs that are present in bacteria and lower eukaryotes. Since all D. discoideum PDEs are now characterized we have calculated the contribution of each enzyme in the degradation of the three important pools of cyclic nucleotides: (i) extracellular cAMP that induces chemotaxis during aggregation and differentiation in slugs; (ii) intracellular cAMP that mediates development; and (iii) intracellular cGMP that mediates chemotaxis. It appears that each cyclic nucleotide pool is degraded by a combination of enzymes that have different affinities, allowing a broad range of substrate concentrations to be degraded with first-order kinetics. Extracellular cAMP is degraded predominantly by the class II high-affinity enzyme DdPDE1 and its close homologue DdPDE7, and in the multicellular stage also by the low-affinity transmembrane class I enzyme DdPDE4. Intracellular cAMP is degraded by the DdPDE2, a class I enzyme regulated by histidine kinase/phospho-relay, and by the cAMP-/cGMP-stimulated class II DdPDE6. Finally, basal intracellular cGMP is degraded predominantly by the high-affinity class I DdPDE3, while the elevated cGMP levels that arise after receptor stimulation are degraded predominantly by a cGMP-stimulated cGMP-specific class II DdPDE5. The analysis shows that the combination of enzymes is tuned to keep the concentration and lifetime of the substrate within a functional range.
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Affiliation(s)
- Sonya Bader
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN, Haren, The Netherlands
| | - Arjan Kortholt
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN, Haren, The Netherlands
| | - Peter J. M. Van Haastert
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN, Haren, The Netherlands
- To whom correspondence should be addressed (email )
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Kolbinger A, Gao T, Brock D, Ammann R, Kisters A, Kellermann J, Hatton D, Gomer RH, Wetterauer B. A cysteine-rich extracellular protein containing a PA14 domain mediates quorum sensing in Dictyostelium discoideum. EUKARYOTIC CELL 2005; 4:991-8. [PMID: 15947191 PMCID: PMC1151990 DOI: 10.1128/ec.4.6.991-998.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Much remains to be understood about quorum-sensing factors that allow cells to sense their local density. Dictyostelium discoideum is a simple eukaryote that grows as single-celled amoebae and switches to multicellular development when food becomes limited. As the growing cells reach a high density, they begin expressing discoidin genes. The cells secrete an unknown factor, and at high cell densities the concomitant high levels of the factor induce discoidin expression. We report here the enrichment of discoidin-inducing complex (DIC), an approximately 400-kDa protein complex that induces discoidin expression during growth and development. Two proteins in the DIC preparation, DicA1 and DicB, were identified by sequencing proteolytic digests. DicA1 and DicB were expressed in Escherichia coli and tested for their ability to induce discoidin during growth and development. Recombinant DicB was unable to induce discoidin expression, while recombinant DicA1 was able to induce discoidin expression. This suggests that DicA1 is an active component of DIC and indicates that posttranslational modification is dispensable for activity. DicA1 mRNA is expressed in vegetative and developing cells. The mature secreted form of DicA1 has a molecular mass of 80 kDa and has a 24-amino-acid cysteine-rich repeat that is similar to repeats in Dictyostelium proteins, such as the extracellular matrix protein ecmB/PstA, the prespore cell-inducing factor PSI, and the cyclic AMP phosphodiesterase inhibitor PDI. Together, the data suggest that DicA1 is a component of a secreted quorum-sensing signal regulating discoidin gene expression during Dictyostelium growth and development.
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Affiliation(s)
- Alexandra Kolbinger
- Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, MS-140, Rice University, 6100 S. Main Street, Houston, TX 77005-1892, USA
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17
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Alvarez-Curto E, Rozen DE, Ritchie AV, Fouquet C, Baldauf SL, Schaap P. Evolutionary origin of cAMP-based chemoattraction in the social amoebae. Proc Natl Acad Sci U S A 2005; 102:6385-90. [PMID: 15851658 PMCID: PMC1088387 DOI: 10.1073/pnas.0502238102] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Indexed: 11/18/2022] Open
Abstract
Phenotypic novelties can arise if integrated developmental pathways are expressed at new developmental stages and then recruited to serve new functions. We analyze the origin of a novel developmental trait of Dictyostelid amoebae: the evolution of cAMP as a developmental chemoattractant. We show that cAMP's role of attracting starving amoebae arose through recruitment of a pathway that originally evolved to coordinate fruiting body morphogenesis. Orthologues of the high-affinity cAMP receptor (cAR), cAR1, were identified in a selection of species that span the Dictyostelid phylogeny. The cAR1 orthologue from the basal species Dictyostelium minutum restored aggregation and development when expressed in an aggregation-defective mutant of the derived species Dictyostelium discoideum that lacks high-affinity cARs, thus demonstrating that the D. minutum cAR is a fully functional cAR. cAR1 orthologues from basal species are expressed during fruiting body formation, and only this process, and not aggregation, was disrupted by abrogation of cAR1 function. This is in contrast to derived species, where cAR1 is also expressed during aggregation and critically regulates this process. Our data show that coordination of fruiting body formation is the ancestral function of extracellular cAMP signaling, whereas its derived role in aggregation evolved by recruitment of a preexisting pathway to an earlier stage of development. This most likely occurred by addition of distal cis-regulatory regions to existing cAMP signaling genes.
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Affiliation(s)
- Elisa Alvarez-Curto
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
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18
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Winckler T, Iranfar N, Beck P, Jennes I, Siol O, Baik U, Loomis WF, Dingermann T. CbfA, the C-module DNA-binding factor, plays an essential role in the initiation of Dictyostelium discoideum development. EUKARYOTIC CELL 2005; 3:1349-58. [PMID: 15470262 PMCID: PMC522599 DOI: 10.1128/ec.3.5.1349-1358.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We recently isolated from Dictyostelium discoideum cells a DNA-binding protein, CbfA, that interacts in vitro with a regulatory element in retrotransposon TRE5-A. We have generated a mutant strain that expresses CbfA at <5% of the wild-type level to characterize the consequences for D. discoideum cell physiology. We found that the multicellular development program leading to fruiting body formation is highly compromised in the mutant. The cells cannot aggregate and stay as a monolayer almost indefinitely. The cells respond properly to prestarvation conditions by expressing discoidin in a cell density-dependent manner. A genomewide microarray-assisted expression analysis combined with Northern blot analyses revealed a failure of CbfA-depleted cells to induce the gene encoding aggregation-specific adenylyl cyclase ACA and other genes required for cyclic AMP (cAMP) signal relay, which is necessary for aggregation and subsequent multicellular development. However, the cbfA mutant aggregated efficiently when mixed with as few as 5% wild-type cells. Moreover, pulsing cbfA mutant cells developing in suspension with nanomolar levels of cAMP resulted in induction of acaA and other early developmental genes. Although the response was less efficient and slower than in wild-type cells, it showed that cells depleted of CbfA are able to initiate development if given exogenous cAMP signals. Ectopic expression of the gene encoding the catalytic subunit of protein kinase A restored multicellular development of the mutant. We conclude that sensing of cell density and starvation are independent of CbfA, whereas CbfA is essential for the pattern of gene expression which establishes the genetic network leading to aggregation and multicellular development of D. discoideum.
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Affiliation(s)
- Thomas Winckler
- Institut für Pharmazeutische Biologie, Universität Frankfurt (Biozentrum), Marie-Curie-Strasse 9, D-60439 Frankfurt, Germany.
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19
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Sun B, Ma H, Firtel RA. Dictyostelium stress-activated protein kinase alpha, a novel stress-activated mitogen-activated protein kinase kinase kinase-like kinase, is important for the proper regulation of the cytoskeleton. Mol Biol Cell 2004; 14:4526-40. [PMID: 14593072 PMCID: PMC266770 DOI: 10.1091/mbc.e03-01-0039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mitogen-activated protein kinase cascades regulate various cellular functions, including growth, cell differentiation, development, and stress responses. We have identified a new Dictyostelium kinase (stress-activated protein kinase [SAPK]alpha), which is related to members of the mixed lineage kinase class of mitogen-activated protein kinase kinases. SAPKalpha is activated by osmotic stress, heat shock, and detachment from the substratum and by a membrane-permeable cGMP analog, a known regulator of stress responses in Dictyostelium. SAPKalpha is important for cellular resistance to stresses, because SAPKalpha null cells exhibit reduced viability in response to osmotic stress. We found that SAPKalpha mutants affect cellular processes requiring proper regulation of the actin cytoskeleton, including cell motility, morphogenesis, cytokinesis, and cell adhesion. Overexpression of SAPKalpha results in highly elevated basal and chemoattractant-stimulated F-actin levels and strong aggregation and developmental defects, including a failure to polarize and chemotax, and abnormal morphogenesis. These phenotypes require a kinase-active SAPKalpha. SAPKalpha null cells exhibit reduced chemoattractant-stimulated F-actin levels, cytokinesis, developmental and adhesion defects, and a motility defect that is less severe than that exhibited by SAPKalpha-overexpressing cells. SAPKalpha colocalizes with F-actin in F-actin-enriched structures, including membrane ruffles and pseudopodia during chemotaxis. Although SAPKalpha is required for these F-actin-mediated processes, it is not detectably activated in response to chemoattractant stimulation.
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Affiliation(s)
- Binggang Sun
- Section of Cell and Developmental Biology, Division of Biological Sciences and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0634, USA
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20
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Saran S, Meima ME, Alvarez-Curto E, Weening KE, Rozen DE, Schaap P. cAMP signaling in Dictyostelium. Complexity of cAMP synthesis, degradation and detection. J Muscle Res Cell Motil 2003; 23:793-802. [PMID: 12952077 DOI: 10.1023/a:1024483829878] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
cAMP plays a pivotal role in control of cell movement, differentiation and response to stress in all phases of the Dictyostelium life cycle. The multitudinous functions of cAMP require precise spatial and temporal control of its production, degradation and detection. Many novel proteins have recently been identified that critically modulate the cAMP signal. We focus in this review on the properties and functions of the three adenylyl cyclases and the three cAMP-phosphodiesterases that are present in Dictyostelium, and the network of proteins that regulate the activity of these enzymes. We also briefly discuss the two modes of detection of cAMP.
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Affiliation(s)
- Shweta Saran
- School of Life Sciences, University of Dundee, MSI/WTB complex, Dundee DD1 5EH, UK
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21
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Iranfar N, Fuller D, Loomis WF. Genome-wide expression analyses of gene regulation during early development of Dictyostelium discoideum. EUKARYOTIC CELL 2003; 2:664-70. [PMID: 12912885 PMCID: PMC178357 DOI: 10.1128/ec.2.4.664-670.2003] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Using genome-wide microarrays, we recognized 172 genes that are highly expressed at one stage or another during multicellular development of Dictyostelium discoideum. When developed in shaken suspension, 125 of these genes were expressed if the cells were treated with cyclic AMP (cAMP) pulses at 6-min intervals between 2 and 6 h of development followed by high levels of exogenous cAMP. In the absence of cAMP treatment, only three genes, carA, gbaB, and pdsA, were consistently expressed. Surprisingly, 14 other genes were induced by cAMP treatment of mutant cells lacking the activatable adenylyl cyclase, ACA. However, these genes were not cAMP induced if both of the developmental adenylyl cyclases, ACA and ACR, were disrupted, showing that they depend on an internal source of cAMP. Constitutive activity of the cAMP-dependent protein kinase PKA was found to bypass the requirement of these genes for adenylyl cyclase and cAMP pulses, demonstrating the critical role of PKA in transducing the cAMP signal to early gene expression. In the absence of constitutive PKA activity, expression of later genes was strictly dependent on ACA in pulsed cells.
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Affiliation(s)
- Negin Iranfar
- Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, California 92093-0368, USA
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22
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Abstract
The Dictyostelium discoideum developmental program is initiated by starvation and its progress depends on G-protein-regulated transmembrane signaling. Disruption of the Dictyostelium G-protein alpha-subunit G alpha 3 (g alpha 3-) blocks development unless the mutant is starved in the presence of artificial cAMP pulses. The function of G alpha 3 was investigated by examining the expression of several components of the cAMP transmembrane signaling system in the g alpha 3- mutant. cAMP receptor 1 protein, cyclic nucleotide phosphodiesterase, phosphodiesterase inhibitor, and aggregation-stage adenylyl cyclase mRNA expression were absent or greatly reduced when cells were starved without exogenously applied pulses of cAMP. However, cAMP receptor 1 protein and aggregation-stage adenylyl cyclase mRNA expression were restored by starving the g alpha 3- cells in the presence of exogenous cAMP pulses. Adenylyl cyclase activity was also reduced in g alpha 3- cells starved without exogenous cAMP pulses compared with similarly treated wild-type cells but was elevated to a level twofold greater than wild-type cells in g alpha 3- cells starved in the presence of exogenous cAMP pulses. These results suggest that G alpha 3 is essential in early development because it controls the expression of components of the transmembrane signaling system.
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Affiliation(s)
- M A Brandon
- Department of Surgery, Wayne State University, Detroit, Michigan 48201, USA
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23
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Miller C, McDonald J, Francis D. Evolution of promoter sequences: elements of a canonical promoter for prespore genes of Dictyostelium. J Mol Evol 1996; 43:185-93. [PMID: 8703084 DOI: 10.1007/bf02338826] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An attempt is made to define a minimal prespore promoter which contains all elements essential for correct regulation of expression of a prespore gene. The prespore genes of Dictyostelium are coregulated during development. Most begin transcription at the same early stage, and activity of all is restricted to prespore tissue during the later slug stage. Sequences 5' to the coding sequences of eight prespore genes were searched for all elements proposed to control transcription and for new elements. The meaningfulness of occurrences of elements and pairs of elements in prespore promoters was evaluated by comparison with frequencies of occurrences in promoters of other, nonprespore genes. These comparisons resulted in definition of a canonical prespore promoter, a stretch of about 200 nucleotides containing at least one of each of three elements. Certain limitations were found on the spacing of elements. Orientation of elements with respect to each other appeared unrestricted. All elements often occurred in multiple copies. This structure suggests that individual copies of each element are not conserved during evolution, but instead continually appear and disappear.
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Affiliation(s)
- C Miller
- Biology Department, University of Oregon, Eugene 97403, USA
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24
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Reymond CD, Schaap P, Véron M, Williams JG. Dual role of cAMP during Dictyostelium development. EXPERIENTIA 1995; 51:1166-74. [PMID: 8536804 DOI: 10.1007/bf01944734] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
cAMP plays an essential role during Dictyostelium development both outside and inside the cell. Membrane-bound receptors and adenylyl cyclase are responsible for sensing and producing extracellular cAMP, whereas a phosphodiesterase is responsible for maintaining a low basal level. The molecular events underlying this type of hormone like signalling, which are now beginning to be deciphered, will be presented, in the light of cAMP analogue studies. The importance of intracellular cAMP for cell differentiation has been demonstrated by the central role of the cAMP dependent protein kinase. Mutants as well as strains obtained by reverse genetics will be reviewed which lead to our current understanding of the role of intracelluar cAMP in the differentiation of both stalk and spore cells.
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Affiliation(s)
- C D Reymond
- University of Lausanne, Institut d'Histologie et d'Embryologie, Switzerland
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25
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Clarke M, Gomer RH. PSF and CMF, autocrine factors that regulate gene expression during growth and early development of Dictyostelium. EXPERIENTIA 1995; 51:1124-34. [PMID: 8536800 DOI: 10.1007/bf01944730] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Throughout growth and development, Dictyostelium cells secrete autocrine factors that accumulate in proportion to cell density. At sufficient concentration, these factors cause changes in gene expression. Vegetative Dictyostelium cells continuously secrete prestarvation factor (PSF). The bacteria upon which the cells feed inhibit their response to PSF, allowing the cells to monitor their own density in relation to that of their food supply. At high PSF/bacteria ratios, which occur during late exponential growth, PSF induces the expression of several genes whose products are needed for cell aggregation. When the food supply has been depleted, PSF production declines, and a second density-sensing pathway is activated. Starving cells secrete conditioned medium factor (CMF), a glycoprotein of Mr 80 kDa that is essential for the development of differentiated cell types. Antisense mutagenesis has shown that cells lacking CMF cannot aggregate, and preliminary data suggest that CMF regulates cAMP signal transduction. Calculations indicate that a mechanism of simultaneously secreting and recognizing a signal molecule, as used by Dictyostelium to monitor cell density, could also be used to determine the total number of cells in a tissue.
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Affiliation(s)
- M Clarke
- Oklahoma Medical Research Foundation, Program in Molecular and Cell Biology, Oklahoma City 73104, USA
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26
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Burdine V, Clarke M. Genetic and physiologic modulation of the prestarvation response in Dictyostelium discoideum. Mol Biol Cell 1995; 6:311-25. [PMID: 7612966 PMCID: PMC301190 DOI: 10.1091/mbc.6.3.311] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Throughout vegetative growth, Dictyostelium amoebae secrete an autocrine factor, prestarvation factor, PSF, which accumulates in proportion to cell density. During late exponential growth, PSF induces the expression of several genes whose products are needed for cAMP signaling and cell aggregation. Among these genes are discoidin-I and the 2.4-kb transcript of cyclic nucleotide phosphodiesterase (PDE). We have identified several parameters that modulate expression of one or both of these prestarvation response genes; all effects were monitored in cells growing exponentially on bacteria. Under these conditions, axenic mutants produce higher levels of PSF activity than wild-type cells. Consistent with the high PSF levels, the 2.4-kb PDE transcript is more abundant in axenic strains than wild-type cells at the same cell density. In contrast, the density-dependent induction of discoidin-I is greatly delayed in axenic strains, occurring only at the very end of exponential growth. Analysis of axenic strains of independent origin suggested that this negative effect on discoidin-I expression is attributable to the axenic mutations themselves. The effects of two environmental factors that inhibit the prestarvation response (the bacteria upon which the cells feed and a bacterial product, folic acid) were also analyzed. We found that folate does not account for the inhibitory effect of bacteria. Cells deficient in the G-protein beta subunit, which is thought to be common to all heterotrimeric G-proteins in Dictyostelium, respond to PSF in the same manner as G beta+ cells, and this response is inhibited by bacteria. However, folate has no inhibitory effect on g beta- cells, indicating that folate inhibition is mediated by a heterotrimeric G-protein. In cells lacking the catalytic subunit of protein kinase A, the prestarvation response is severely impaired, but about 3% of the pka- cells manifest an apparently normal density-dependent induction of discoidin-I. This behavior and the heterogeneity of the prestarvation response in wild-type cells lead us to speculate that protein kinase A may not be required for PSF signal transduction per se, but rather may render the cells responsive to PSF. Based on analysis of adenylyl cyclase mutants (aca-), the effect of protein kinase A is not cAMP-dependent.
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Affiliation(s)
- V Burdine
- Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104, USA
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27
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Traynor D, Kessin RH, Williams JG. Chemotactic sorting to cAMP in the multicellular stages of Dictyostelium development. Proc Natl Acad Sci U S A 1992; 89:8303-7. [PMID: 1325653 PMCID: PMC49906 DOI: 10.1073/pnas.89.17.8303] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dictyostelium transformants that overproduce the extracellular form of cyclic nucleotide phosphodiesterase and so accumulate a reduced amount of cAMP are blocked in development after aggregation in the form of a tight mound, prior to formation of the apical tip. In such mounds, prespore cell differentiation is repressed, and the apical accumulation of prestalk cells is greatly retarded. When a source of cAMP is placed below the arrested mounds, prestalk cells that would normally migrate in an apical direction instead sort downwards to the substratum. Thus, by acting as the chemoattractant that draws prestalk cells to the apex, cAMP signaling directs the formation of a patterned structure.
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Affiliation(s)
- D Traynor
- Imperial Cancer Research Fund, Clare Hall Laboratory, Potters Bar, Herts, United Kingdom
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28
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Louvion JF, Scholder JC, Pinaud S, Reymond CD. Two independent promoters as well as 5' untranslated regions regulate Dd ras expression in Dictyostelium. Nucleic Acids Res 1991; 19:6133-8. [PMID: 1659685 PMCID: PMC329103 DOI: 10.1093/nar/19.22.6133] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Dd ras gene produces three transcripts during Dictyostelium development. The largest transcript (L-) can be induced by external addition of cAMP even in cells prevented from aggregating, whereas shorter transcripts (S1- and S2-) expression requires cell aggregate formation. We show the presence of two independent promoters for L- and S-transcripts by deletion analysis of Dd ras fragments fused to CAT reporter genes reintroduced in Dictyostelium. A direct repeat upstream of S-transcript start sites which seems involved in S-promoter function, modulates also L-RNA accumulation. Furthermore removal of sequences between this repeat and the AUG protein start codon reduces the level of L-transcripts in aggregates. This study allowed to uncover the intricate pattern of sequences participating in the regulation of Dd ras expression.
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Affiliation(s)
- J F Louvion
- Swiss Institute for Experimental Cancer Research, ISREC, CH-1066 Epalinges
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29
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Identification of a protein kinase multigene family of Dictyostelium discoideum: molecular cloning and expression of a cDNA encoding a developmentally regulated protein kinase. Proc Natl Acad Sci U S A 1991; 88:1115-9. [PMID: 1996312 PMCID: PMC50967 DOI: 10.1073/pnas.88.4.1115] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have identified protein kinase genes of Dictyostelium by using highly conserved amino acid sequence motifs to design the synthesis and amplification of DNA fragments by polymerase chain reactions (PCRs). Cloning and sequencing the PCR products have revealed five different members of the protein kinase multigene family. These five putative kinases showed varying degrees of amino acid sequence similarity (40-70%) to protein kinases in data bases and contained invariant amino acid residues characteristic of protein kinases. DNA from PCR was labeled and used to isolate several lambda gt11 cDNA clones, including one full-length one (Dd kinase-2). The nucleotide sequence of Dd kinase-2 contained a region identical to one of the cloned kinase fragments amplified by PCR, and based on the deduced amino acid sequence Dd kinase-2 encodes a protein of 479 amino acids. A 350-amino acid kinase domain at the C-terminal end shows high homology to the catalytic domains of protein kinase A, protein kinase C, S-6 kinase of Xenopus, and the suppressor of cdc25 of yeast. The N-terminal domain is highly basic and also contains alternating threonine/proline residues. The cDNA hybridized to a single copy gene but to two differentially regulated mRNAs--a 2.0-kilobase mRNA that is expressed in vegetative cells and a 2.2-kilobase mRNA that is expressed during development. The larger mRNA is induced by cAMP by using a cell-surface receptor-mediated signal transduction pathway.
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30
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Maniak M, Nellen W. Evidence for a feedback regulated back-up promoter which controls permanent expression of a Dictyostelium gene. Nucleic Acids Res 1990; 18:5375-80. [PMID: 2216709 PMCID: PMC332212 DOI: 10.1093/nar/18.18.5375] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have previously described the elements of two overlapping promoters regulating differential expression of the Dictyostelium P8A7 gene. One promoter was constitutively active but stimulated during development (S-promoter), while the other (L-promoter) was found to be induced by a variety of stimuli. This effect was mediated by the induction (i-) element. By a series of antisense transformation experiments we here provide evidence that this element is the target of a feedback control circuit. In wild type cells, feedback regulation activates the L-promoter in unfavourable environmental situations when transcription from the S-promoter is insufficient to generate adequate amounts of protein. A model for the function of the feedback loop under natural and experimental conditions is presented.
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Affiliation(s)
- M Maniak
- Max-Planck-Institut für Biochemie, Abt. Zellbiologie, Martinsried, FRG
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