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Watanabe M, Ikeuchi M, Wilde A. The organization of the phycobilisome-photosystem I supercomplex depends on the ratio between two different phycobilisome linker proteins. Photochem Photobiol Sci 2023:10.1007/s43630-023-00397-2. [PMID: 36859522 DOI: 10.1007/s43630-023-00397-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 02/16/2023] [Indexed: 03/03/2023]
Abstract
The phycobilisome (PBS) is an antenna protein complex in cyanobacteria, Glaucocystophytes, and red algae. In the standard PBS, the rod-core PBS, the rods are connected to the core by the rod-core linker protein CpcG. The rod-core PBS transfers the light energy mainly to photosystem (PS) II and to a lesser extent to PSI. Cyanobacteria assemble another type of PBS, the CpcL-PBS, which consists of only one rod. This rod-type PBS is connected to the thylakoid membrane by the linker protein CpcL and is a PSI-specific antenna. In the filamentous heterocyst-forming cyanobacterium Anabaena (Nostoc) sp. PCC 7120, the CpcL-PBS forms a complex with the tetrameric PSI (PBS-PSI supercomplex). The CpcL-PBS and the rod part of the rod-core PBS are identical except for the linker proteins CpcL and CpcG. How cells control the accumulation of the two different types of PBS is unknown. Here, we analyzed two mutant strains which either lack the major rod-core linker CpcG4 or overexpress the rod-membrane linker CpcL. In both mutant strains, more and larger PBS-PSI supercomplexes accumulated compared to the wild type. Our results suggest that CpcL and CpcG4 compete for the same phycobiliprotein pool, and therefore the CpcL/CpcG4 ratio determines the levels of PBS-PSI supercomplexes. We propose that the CpcL-PBS and the rod-core PBS fulfill distinct functions in light harvesting.
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Affiliation(s)
- Mai Watanabe
- Faculty of Biology, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany. .,Department of Life Sciences (Biology), Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro, Tokyo, 153-8902, Japan. .,Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Minami-Ohsawa, Hachioji, Tokyo, 192-0397, Japan.
| | - Masahiko Ikeuchi
- Department of Life Sciences (Biology), Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro, Tokyo, 153-8902, Japan
| | - Annegret Wilde
- Faculty of Biology, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
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2
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Casanova-Ferrer P, Muñoz-García J, Ares S. Mathematical models of nitrogen-fixing cell patterns in filamentous cyanobacteria. Front Cell Dev Biol 2022; 10:959468. [PMID: 36187490 PMCID: PMC9523125 DOI: 10.3389/fcell.2022.959468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/25/2022] [Indexed: 11/13/2022] Open
Abstract
The Anabaena genus is a model organism of filamentous cyanobacteria whose vegetative cells can differentiate under nitrogen-limited conditions into a type of cell called a heterocyst. These heterocysts lose the possibility to divide and are necessary for the filament because they can fix and share environmental nitrogen. In order to distribute the nitrogen efficiently, heterocysts are arranged to form a quasi-regular pattern whose features are maintained as the filament grows. Recent efforts have allowed advances in the understanding of the interactions and genetic mechanisms underlying this dynamic pattern. Here, we present a systematic review of the existing theoretical models of nitrogen-fixing cell differentiation in filamentous cyanobacteria. These filaments constitute one of the simplest forms of multicellular organization, and this allows for several modeling scales of this emergent pattern. The system has been approached at three different levels. From bigger to smaller scale, the system has been considered as follows: at the population level, by defining a mean-field simplified system to study the ratio of heterocysts and vegetative cells; at the filament level, with a continuous simplification as a reaction-diffusion system; and at the cellular level, by studying the genetic regulation that produces the patterning for each cell. In this review, we compare these different approaches noting both the virtues and shortcomings of each one of them.
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Affiliation(s)
- Pau Casanova-Ferrer
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
- Centro Nacional de Biotecnologia (CNB), CSIC, Madrid, Spain
| | - Javier Muñoz-García
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
| | - Saúl Ares
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Centro Nacional de Biotecnologia (CNB), CSIC, Madrid, Spain
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Casanova-Ferrer P, Ares S, Muñoz-García J. Terminal heterocyst differentiation in the Anabaena patA mutant as a result of post-transcriptional modifications and molecular leakage. PLoS Comput Biol 2022; 18:e1010359. [PMID: 35969646 PMCID: PMC9410556 DOI: 10.1371/journal.pcbi.1010359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 08/25/2022] [Accepted: 07/05/2022] [Indexed: 12/27/2022] Open
Abstract
The Anabaena genus is a model organism of filamentous cyanobacteria whose vegetative cells can differentiate under nitrogen-limited conditions into a type of cell called heterocyst. These heterocysts lose the possibility to divide and are necessary for the colony because they can fix and share environmental nitrogen. In order to distribute the nitrogen efficiently, heterocysts are arranged to form a quasi-regular pattern whose features are maintained as the filament grows. Recent efforts have allowed advances in the understanding of the interactions and genetic mechanisms underlying this dynamic pattern. However, the main role of the patA and hetF genes are yet to be clarified; in particular, the patA mutant forms heterocysts almost exclusively in the terminal cells of the filament. In this work, we investigate the function of these genes and provide a theoretical model that explains how they interact within the broader genetic network, reproducing their knock-out phenotypes in several genetic backgrounds, including a nearly uniform concentration of HetR along the filament for the patA mutant. Our results suggest a role of hetF and patA in a post-transcriptional modification of HetR which is essential for its regulatory function. In addition, the existence of molecular leakage out of the filament in its boundary cells is enough to explain the preferential appearance of terminal heterocysts, without any need for a distinct regulatory pathway. Understanding multicellular pattern formation is key for the study of both natural and synthetic developmental processes. Arguably one of the simplest model systems for this is the filamentous cyanobacterium Anabaena, that in conditions of nitrogen deprivation undergoes a dynamical differentiation process that differentiates roughly one in every ten cells into nitrogen-fixing heterocysts, in a quasi-regular pattern that is maintained as the filament keeps growing. One of the most characteristic mutations affecting this process forms heterocysts mostly constrained to the terminal cells of the filament. We have used experimental observations to propose a mathematical model of heterocyst differentiation able to reproduce this striking phenotype. The model extends our understanding of the regulations in this pattern-forming system and makes several predictions on molecular interactions. Importantly, a key aspect is the boundary condition at the filament’s ends: inhibitors of differentiation should be able to leak out of the filament, or otherwise the terminal cells would not differentiate. This highlights, in a very clear example, the importance of considering physical constraints in developmental processes.
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Affiliation(s)
- Pau Casanova-Ferrer
- Grupo Interdisciplinar de Sistemas Complejos (GISC) and Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
- Centro Nacional de Biotecnologia (CNB), CSIC, Madrid, Spain
| | - Saúl Ares
- Grupo Interdisciplinar de Sistemas Complejos (GISC) and Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
- Centro Nacional de Biotecnologia (CNB), CSIC, Madrid, Spain
- * E-mail: (SA); (JM-G)
| | - Javier Muñoz-García
- Grupo Interdisciplinar de Sistemas Complejos (GISC) and Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
- * E-mail: (SA); (JM-G)
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The Heterocyst-Specific Small RNA NsiR1 Regulates the Commitment to Differentiation in Nostoc. Microbiol Spectr 2022; 10:e0227421. [PMID: 35230129 PMCID: PMC9045159 DOI: 10.1128/spectrum.02274-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Heterocysts are specialized cells that filamentous cyanobacteria differentiate for the fixation of atmospheric nitrogen when other nitrogen sources are not available. Heterocyst differentiation at semiregular intervals along the filaments requires complex structural and metabolic changes that are under the control of the master transcriptional regulator HetR. NsiR1 (nitrogen stress-induced RNA 1) is a HetR-dependent noncoding RNA that is expressed from multiple chromosomal copies, some identical, some slightly divergent in sequence, specifically in heterocysts from very early stages of differentiation. We have previously shown that NsiR1 inhibits translation of the overlapping hetF mRNA by an antisense mechanism. Here, we identify alr3234, a hetP-like gene involved in the regulation of commitment (point of no return) to heterocyst differentiation, as a target of NsiR1. A strain overexpressing one of the identical copies of NsiR1 commits to heterocyst development earlier than the wild type. The posttranscriptional regulation exerted by NsiR1 on the expression of two genes involved in heterocyst differentiation and commitment, hetF and alr3234, adds a new level of complexity to the network of transcriptional regulation and protein-protein interactions that participate in heterocyst differentiation. IMPORTANCE Heterocysts are nitrogen-fixing specialized cells that appear at semiregular intervals along cyanobacterial filaments upon nitrogen starvation. The differentiation and patterning of heterocysts is a model for the study of cell differentiation in multicellular prokaryotes. The regulation of differentiation, which is only partially understood, includes transcriptional changes, factor diffusion between cells, and protein-protein interactions. This work describes the identification of a novel target for NsiR1, a small RNA (sRNA) encoded in multiple slightly divergent copies, and shows how different copies of “sibling” sRNAs regulate the expression of different targets involved in one of the few examples of a differentiation process in prokaryotes.
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Sarasa-Buisan C, Guio J, Broset E, Peleato ML, Fillat MF, Sevilla E. FurC (PerR) from Anabaena sp. PCC7120: a versatile transcriptional regulator engaged in the regulatory network of heterocyst development and nitrogen fixation. Environ Microbiol 2021; 24:566-582. [PMID: 33938105 DOI: 10.1111/1462-2920.15552] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/19/2021] [Accepted: 04/30/2021] [Indexed: 11/29/2022]
Abstract
FurC (PerR) from Anabaena sp. PCC7120 was previously described as a key transcriptional regulator involved in setting off the oxidative stress response. In the last years, the cross-talk between oxidative stress, iron homeostasis and nitrogen metabolism is becoming more and more evident. In this work, the transcriptome of a furC-overexpressing strain was compared with that of a wild-type strain under both standard and nitrogen-deficiency conditions. The results showed that the overexpression of furC deregulates genes involved in several categories standing out photosynthesis, iron transport and nitrogen metabolism. The novel FurC-direct targets included some regulatory elements that control heterocyst development (hetZ and asr1734), genes directly involved in the heterocyst envelope formation (devBCA and hepC) and genes which participate in the nitrogen fixation process (nifHDK and nifH2, rbrA rubrerythrin and xisHI excisionase). Likewise, furC overexpression notably impacts the mRNA levels of patA encoding a key protein in the heterocyst pattern formation. The relevance of FurC in these processes is bringing out by the fact that the overexpression of furC impairs heterocyst development and cell growth under nitrogen step-down conditions. In summary, this work reveals a new player in the complex regulatory network of heterocyst formation and nitrogen fixation.
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Affiliation(s)
- Cristina Sarasa-Buisan
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Jorge Guio
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Esther Broset
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - M Luisa Peleato
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - María F Fillat
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Emma Sevilla
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
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6
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Inactivation of Three RG(S/T)GR Pentapeptide-Containing Negative Regulators of HetR Results in Lethal Differentiation of Anabaena PCC 7120. Life (Basel) 2020; 10:life10120326. [PMID: 33291589 PMCID: PMC7761841 DOI: 10.3390/life10120326] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/27/2020] [Accepted: 12/01/2020] [Indexed: 12/19/2022] Open
Abstract
The filamentous cyanobacterium Anabaena sp. PCC 7120 produces, during the differentiation of heterocysts, a short peptide PatS and a protein HetN, both containing an RGSGR pentapeptide essential for activity. Both act on the master regulator HetR to guide heterocyst pattern formation by controlling the binding of HetR to DNA and its turnover. A third small protein, PatX, with an RG(S/T)GR motif is present in all HetR-containing cyanobacteria. In a nitrogen-depleted medium, inactivation of patX does not produce a discernible change in phenotype, but its overexpression blocks heterocyst formation. Mutational analysis revealed that PatX is not required for normal intercellular signaling, but it nonetheless is required when PatS is absent to prevent rapid ectopic differentiation. Deprivation of all three negative regulators—PatS, PatX, and HetN—resulted in synchronous differentiation. However, in a nitrogen-containing medium, such deprivation leads to extensive fragmentation, cell lysis, and aberrant differentiation, while either PatX or PatS as the sole HetR regulator can establish and maintain a semiregular heterocyst pattern. These results suggest that tight control over HetR by PatS and PatX is needed to sustain vegetative growth and regulated development. The mutational analysis has been interpreted in light of the opposing roles of negative regulators of HetR and the positive regulator HetL.
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Brenes‐Álvarez M, Minguet M, Vioque A, Muro‐Pastor AM. NsiR1, a smallRNAwith multiple copies, modulates heterocyst differentiation in the cyanobacteriumNostocsp.PCC7120. Environ Microbiol 2020; 22:3325-3338. [DOI: 10.1111/1462-2920.15103] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/22/2020] [Accepted: 05/24/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Manuel Brenes‐Álvarez
- Instituto de Bioquímica Vegetal y Fotosíntesis Consejo Superior de Investigaciones Científicas and Universidad de Sevilla Sevilla Spain
| | - Marina Minguet
- Instituto de Bioquímica Vegetal y Fotosíntesis Consejo Superior de Investigaciones Científicas and Universidad de Sevilla Sevilla Spain
| | - Agustín Vioque
- Instituto de Bioquímica Vegetal y Fotosíntesis Consejo Superior de Investigaciones Científicas and Universidad de Sevilla Sevilla Spain
| | - Alicia M. Muro‐Pastor
- Instituto de Bioquímica Vegetal y Fotosíntesis Consejo Superior de Investigaciones Científicas and Universidad de Sevilla Sevilla Spain
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8
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Álvarez-Escribano I, Brenes-Álvarez M, Olmedo-Verd E, Vioque A, Muro-Pastor AM. The Nitrogen Stress-Repressed sRNA NsrR1 Regulates Expression of all1871, a Gene Required for Diazotrophic Growth in Nostoc sp. PCC 7120. Life (Basel) 2020; 10:life10050054. [PMID: 32365616 PMCID: PMC7281752 DOI: 10.3390/life10050054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 04/26/2020] [Accepted: 04/27/2020] [Indexed: 12/14/2022] Open
Abstract
Small regulatory RNAs (sRNAs) are post-transcriptional regulators of bacterial gene expression. In cyanobacteria, the responses to nitrogen availability, that are mostly controlled at the transcriptional level by NtcA, involve also at least two small RNAs, namely NsiR4 (nitrogen stress-induced RNA 4) and NsrR1 (nitrogen stress-repressed RNA 1). Prediction of possible mRNA targets regulated by NsrR1 in Nostoc sp. PCC 7120 allowed, in addition to previously described nblA, the identification of all1871, a nitrogen-regulated gene encoding a protein of unknown function that we describe here as required for growth at the expense of atmospheric nitrogen (N2). We show that transcription of all1871 is induced upon nitrogen step-down independently of NtcA. All1871 accumulation is repressed by NsrR1 and its expression is stronger in heterocysts, specialized cells devoted to N2 fixation. We demonstrate specific interaction between NsrR1 and the 5′ untranslated region (UTR) of the all1871 mRNA, that leads to decreased expression of all1871. Because transcription of NsrR1 is partially repressed by NtcA, post-transcriptional regulation by NsrR1 would constitute an indirect way of NtcA-mediated regulation of all1871.
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Sevilla E, Sarasa-Buisan C, González A, Cases R, Kufryk G, Peleato ML, Fillat MF. Regulation by FurC in Anabaena Links the Oxidative Stress Response to Photosynthetic Metabolism. PLANT & CELL PHYSIOLOGY 2019; 60:1778-1789. [PMID: 31111929 DOI: 10.1093/pcp/pcz094] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/10/2019] [Indexed: 06/09/2023]
Abstract
The FUR (Ferric Uptake Regulator) family in Anabaena sp. PCC 7120 consists of three paralogs named FurA (Fur), FurB (Zur) and FurC (PerR). furC seems to be an essential gene in the filamentous nitrogen-fixing strain Anabaena sp. PCC 7120, suggesting that it plays a fundamental role in this organism. In order to better understand the functions of FurC in Anabaena, the phenotype of a derivative strain that overexpresses this regulator (EB2770FurC) has been characterized. The furC-overexpressing variant presented alterations in growth rate, morphology and ultrastructure, as well as higher sensitivity to peroxide than Anabaena sp. PCC 7120. Interestingly, the overexpression of furC led to reduced photosynthetic O2 evolution, increased respiratory activity, and had a significant influence in the composition and efficiency of both photosystems. Comparative transcriptional analyses, together with electrophoretic mobility shift assays allowed the identification of different genes directly controlled by FurC, and involved in processes not previously related to PerR proteins, such as the cell division gene ftsZ and the major thylakoid membrane protease ftsH. The rise in the transcription of ftsH in EB2770FurC cells correlated with reduced levels of the D1 protein, which is involved in the PSII repair cycle. Deregulation of the oxidative stress response in EB2770FurC cells led to the identification of novel FurC targets involved in the response to H2O2 through different mechanisms. These results, together with the effect of furC overexpression on the composition, stability and efficiency of the photosynthetic machinery of Anabaena, disclose novel links between PerR proteins, cell division and photosynthesis in filamentous cyanobacteria.
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Affiliation(s)
- Emma Sevilla
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
| | - Cristina Sarasa-Buisan
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
| | - Andrés González
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Aragon Institute for Health Research (IIS Aragón), Zaragoza, Spain
| | - Rafael Cases
- Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad de Zaragoza-CSIC, Zaragoza, Spain
| | - Galyna Kufryk
- College of Science, Engineering and Technology, Grand Canyon University, 3300 W. Camelback Rd, Phoenix, AZ, USA
| | - M Luisa Peleato
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
| | - María F Fillat
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
- Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, Spain
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10
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Functional Overlap of hetP and hetZ in Regulation of Heterocyst Differentiation in Anabaena sp. Strain PCC 7120. J Bacteriol 2018; 200:JB.00707-17. [PMID: 29440250 DOI: 10.1128/jb.00707-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 02/05/2018] [Indexed: 11/20/2022] Open
Abstract
HetR plays a key role in regulation of heterocyst differentiation and patterning in Anabaena It directly regulates genes involved in heterocyst differentiation (such as hetP and hetZ), genes involved in pattern formation (patA), and many others. In this study, we investigated the functional relationship of hetP and hetZ and their role in HetR-dependent cell differentiation. Coexpression of hetP and hetZ from the promoter of ntcA, which encodes the global nitrogen regulator, enabled a hetR mutant to form heterocysts with low aerobic nitrogenase activity. Overexpression of hetZ restored heterocyst differentiation in a hetP mutant and vice versa. Overexpression of hetR restored heterocyst formation in either a hetP or a hetZ mutant but not in a hetZ hetP double mutant. The functional overlap of hetP and hetZ was further confirmed by reverse transcription-quantitative PCR (RT-qPCR) and transcriptomic analyses of their effects on gene expression. In addition, yeast two-hybrid and pulldown assays showed the interaction of HetZ with HetR. HetP and HetZ are proposed as the two major factors that control heterocyst formation in response to upregulation of hetRIMPORTANCE Heterocyst-forming cyanobacteria contribute significantly to N2 fixation in marine, freshwater, and terrestrial ecosystems. Formation of heterocysts enables this group of cyanobacteria to fix N2 efficiently under aerobic conditions. HetR, HetP, and HetZ are among the most important factors involved in heterocyst differentiation. We present evidence for the functional overlap of hetP and hetZ and for the key role of the HetR-HetP/HetZ circuit in regulation of heterocyst differentiation. The regulatory mechanism based on HetR, HetP, and HetZ is probably conserved in all heterocyst-forming cyanobacteria.
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11
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González A, Sevilla E, Bes MT, Peleato ML, Fillat MF. Pivotal Role of Iron in the Regulation of Cyanobacterial Electron Transport. Adv Microb Physiol 2016; 68:169-217. [PMID: 27134024 DOI: 10.1016/bs.ampbs.2016.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-containing metalloproteins are the main cornerstones for efficient electron transport in biological systems. The abundance and diversity of iron-dependent proteins in cyanobacteria makes those organisms highly dependent of this micronutrient. To cope with iron imbalance, cyanobacteria have developed a survey of adaptation strategies that are strongly related to the regulation of photosynthesis, nitrogen metabolism and other central electron transfer pathways. Furthermore, either in its ferrous form or as a component of the haem group, iron plays a crucial role as regulatory signalling molecule that directly or indirectly modulates the composition and efficiency of cyanobacterial redox reactions. We present here the major mechanism used by cyanobacteria to couple iron homeostasis to the regulation of electron transport, making special emphasis in processes specific in those organisms.
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Affiliation(s)
| | - E Sevilla
- University of Zaragoza, Zaragoza, Spain
| | - M T Bes
- University of Zaragoza, Zaragoza, Spain
| | | | - M F Fillat
- University of Zaragoza, Zaragoza, Spain.
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12
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Sein-Echaluce VC, González A, Napolitano M, Luque I, Barja F, Peleato ML, Fillat MF. Zur (FurB) is a key factor in the control of the oxidative stress response inAnabaenasp. PCC 7120. Environ Microbiol 2014; 17:2006-17. [DOI: 10.1111/1462-2920.12628] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 01/08/2023]
Affiliation(s)
- Violeta C. Sein-Echaluce
- Departamento de Bioquímica y Biología Molecular y Celular; Instituto de Biocomputación y Física de Sistemas Complejos; Universidad de Zaragoza; Zaragoza 50009 Spain
| | - Andrés González
- Departamento de Bioquímica y Biología Molecular y Celular; Instituto de Biocomputación y Física de Sistemas Complejos; Universidad de Zaragoza; Zaragoza 50009 Spain
| | - Mauro Napolitano
- Instituto de Bioquímica Vegetal y Fotosíntesis; CSIC-Universidad de Sevilla; Sevilla E-41092 Spain
| | - Ignacio Luque
- Instituto de Bioquímica Vegetal y Fotosíntesis; CSIC-Universidad de Sevilla; Sevilla E-41092 Spain
| | - Francisco Barja
- Microbiology Unit; Botany and Plant Biology Department; University of Geneva; Ch. Des Embrouchis 10 Jussy-Geneva CH-1254 Switzerland
| | - M. Luisa Peleato
- Departamento de Bioquímica y Biología Molecular y Celular; Instituto de Biocomputación y Física de Sistemas Complejos; Universidad de Zaragoza; Zaragoza 50009 Spain
| | - María F. Fillat
- Departamento de Bioquímica y Biología Molecular y Celular; Instituto de Biocomputación y Física de Sistemas Complejos; Universidad de Zaragoza; Zaragoza 50009 Spain
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13
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Osanai T, Oikawa A, Iijima H, Kuwahara A, Asayama M, Tanaka K, Ikeuchi M, Saito K, Hirai MY. Metabolomic analysis reveals rewiring of Synechocystis sp. PCC 6803 primary metabolism by ntcA overexpression. Environ Microbiol 2014; 16:3304-17. [PMID: 25039649 DOI: 10.1111/1462-2920.12554] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Accepted: 06/30/2014] [Indexed: 11/26/2022]
Abstract
NtcA is a cAMP receptor protein-type transcription factor conserved among cyanobacteria and is essential for gene expression in response to nitrogen status. NtcA has been widely studied; however, no metabolomic analysis has been conducted using the ntcA mutant. Here, we generated a strain that overexpresses ntcA in Synechocystis sp. PCC 6803, named NOX10, and performed physiological, transcriptomic and metabolomic analyses. NOX10 grew faster than the wild-type strain under photoautotrophic conditions, but slower under light-activated heterotrophic conditions. Transcriptome analysis revealed that the expression of genes related to primary metabolism was altered by ntcA overexpression particularly under nitrogen-depleted conditions. Metabolomic analysis revealed that metabolite levels in sugar, purine/pyrimidine nucleotide, organic acid and amino acid metabolism were widely altered by ntcA overexpression. The protein levels of nitrogen-regulated transcriptional regulators were altered by ntcA overexpression during nitrogen starvation. These results demonstrate the alteration of primary metabolism by genetic engineering of NtcA, and they contribute to the current understanding of metabolic regulation of unicellular cyanobacteria.
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Affiliation(s)
- Takashi Osanai
- RIKEN, Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan; Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
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González A, Angarica VE, Sancho J, Fillat MF. The FurA regulon in Anabaena sp. PCC 7120: in silico prediction and experimental validation of novel target genes. Nucleic Acids Res 2014; 42:4833-46. [PMID: 24503250 PMCID: PMC4005646 DOI: 10.1093/nar/gku123] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In the filamentous cyanobacterium Anabaena sp. PCC 7120, the ferric uptake regulator FurA functions as a global transcriptional regulator. Despite several analyses have focused on elucidating the FurA-regulatory network, the number of target genes described for this essential transcription factor is limited to a handful of examples. In this article, we combine an in silico genome-wide predictive approach with experimental determinations to better define the FurA regulon. Predicted FurA-binding sites were identified upstream of 215 genes belonging to diverse functional categories including iron homeostasis, photosynthesis and respiration, heterocyst differentiation, oxidative stress defence and light-dependent signal transduction mechanisms, among others. The probabilistic model proved to be effective at discerning FurA boxes from non-cognate sequences, while subsequent electrophoretic mobility shift assay experiments confirmed the in vitro specific binding of FurA to at least 20 selected predicted targets. Gene-expression analyses further supported the dual role of FurA as transcriptional modulator that can act both as repressor and as activator. In either role, the in vitro affinity of the protein to its target sequences is strongly dependent on metal co-regulator and reducing conditions, suggesting that FurA couples in vivo iron homeostasis and the response to oxidative stress to major physiological processes in cyanobacteria.
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Affiliation(s)
- Andrés González
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009 Zaragoza, Spain, Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, 50018 Zaragoza, Spain and Unidad Asociada BIFI-IQFR (CSIC), 28006 Madrid, Spain
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Picossi S, Flores E, Herrero A. ChIP analysis unravels an exceptionally wide distribution of DNA binding sites for the NtcA transcription factor in a heterocyst-forming cyanobacterium. BMC Genomics 2014; 15:22. [PMID: 24417914 PMCID: PMC3898017 DOI: 10.1186/1471-2164-15-22] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 12/26/2013] [Indexed: 11/20/2022] Open
Abstract
Background The CRP-family transcription factor NtcA, universally found in cyanobacteria, was initially discovered as a regulator operating N control. It responds to the N regime signaled by the internal 2-oxoglutarate levels, an indicator of the C to N balance of the cells. Canonical NtcA-activated promoters bear an NtcA-consensus binding site (GTAN8TAC) centered at about 41.5 nucleotides upstream from the transcription start point. In strains of the Anabaena/Nostoc genera NtcA is pivotal for the differentiation of heterocysts in response to N stress. Results In this study, we have used chromatin immunoprecipitation followed by high-throughput sequencing to identify the whole catalog of NtcA-binding sites in cells of the filamentous, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 three hours after the withdrawal of combined N. NtcA has been found to bind to 2,424 DNA regions in the genome of Anabaena, which have been ascribed to 2,153 genes. Interestingly, only a small proportion of those genes are involved in N assimilation and metabolism, and 65% of the binding regions were located intragenically. Conclusions The distribution of NtcA-binding sites identified here reveals the largest bacterial regulon described to date. Our results show that NtcA has a much wider role in the physiology of the cell than it has been previously thought, acting both as a global transcriptional regulator and possibly also as a factor influencing the superstructure of the chromosome (and plasmids).
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Affiliation(s)
- Silvia Picossi
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, Seville E-41092, Spain.
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González A, Valladares A, Peleato ML, Fillat MF. FurA influences heterocyst differentiation in Anabaena sp. PCC 7120. FEBS Lett 2013; 587:2682-90. [PMID: 23851073 DOI: 10.1016/j.febslet.2013.07.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/01/2013] [Accepted: 07/02/2013] [Indexed: 01/14/2023]
Abstract
In Anabaena sp. PCC 7120, FurA is a global transcriptional regulator whose expression is strongly induced by NtcA in proheterocysts and remains stably expressed in mature heterocysts. In the present study, overexpression of furA partially suppressed heterocyst differentiation by impairing morphogenesis at an early stage. Recombinant purified FurA specifically bound in vitro to the promoter regions of ntcA, while quantitative RT-PCR analyses indicated that furA overexpression strongly affected the transient increase of ntcA expression that occurs shortly after nitrogen step-down. Overall, the results suggest a connection between iron homeostasis and heterocyst differentiation via FurA, by modulating the expression of ntcA.
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Affiliation(s)
- Andrés González
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009 Zaragoza, Spain
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González A, Bes MT, Valladares A, Peleato ML, Fillat MF. FurA is the master regulator of iron homeostasis and modulates the expression of tetrapyrrole biosynthesis genes inAnabaenasp. PCC 7120. Environ Microbiol 2012; 14:3175-87. [DOI: 10.1111/j.1462-2920.2012.02897.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/06/2012] [Accepted: 09/09/2012] [Indexed: 12/15/2022]
Affiliation(s)
| | | | - Ana Valladares
- Instituto de Bioquímica Vegetal y Fotosíntesis; Centro de Investigaciones Científicas Isla de la Cartuja; CSIC-Universidad de Sevilla; E-41092; Seville; Spain
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Transformation and conjugal transfer of foreign genes into the filamentous multicellular cyanobacteria (subsection V) Fischerella and Chlorogloeopsis. Curr Microbiol 2012; 65:552-60. [PMID: 22833222 DOI: 10.1007/s00284-012-0193-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 06/20/2012] [Indexed: 10/28/2022]
Abstract
Cyanobacteria of subsection V grow as filaments with asymmetrical cell divisions that can generate a true-branching phenotype. Members of the genera Fischerella and Chlorogloeopsis furthermore differentiate akinetes (spore-like resting stages), heterocysts (specialized in nitrogen fixation) and hormogonia (cell aggregates with gliding motility for colonization and dispersal). Genetic approaches to studying the complex morphology and differentiations of these prokaryotes require transformation techniques. For Fischerella and Chlorogloeopsis reliable protocols for introducing foreign genes are lacking. Here, we explored conjugation, electroporation, and biolistic DNA transfer methods in Fischerella and Chlorogloeopsis, using the cyanobacterial replicon pRL25C as a marker. We successfully transformed Fischerella muscicola PCC 7414 and Chlorogloeopsis fritschii PCC 6912 and were able to express the GFP reporter protein under two different promoters: the nitrogen regulated (p) glnA and the strong E. coli hybrid (p) trc. For Fischerella all methods worked, for Chlorogloeopsis electroporation was unsuccessful. For both strains conjugation delivered the most reproducible results, whereby partial removal of the exopolysaccharide sheath by salt washing was a critical step.
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A major facilitator superfamily protein, HepP, is involved in formation of the heterocyst envelope polysaccharide in the cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2012; 194:4677-87. [PMID: 22753066 DOI: 10.1128/jb.00489-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some filamentous cyanobacteria such as Anabaena sp. strain PCC 7120 produce cells, termed heterocysts, specialized in nitrogen fixation. Heterocysts bear a thick envelope containing an inner layer of glycolipids and an outer layer of polysaccharide that restrict the diffusion of air (including O(2)) into the heterocyst. Anabaena sp. mutants impaired in production of either of those layers show a Fox(-) phenotype (requiring fixed nitrogen for growth under oxic conditions). We have characterized a set of transposon-induced Fox(-) mutants in which transposon Tn5-1063 was inserted into the Anabaena sp. chromosome open reading frame all1711 which encodes a predicted membrane protein that belongs to the major facilitator superfamily (MFS). These mutants showed higher nitrogenase activities under anoxic than under oxic conditions and altered sucrose uptake. Electron microscopy and alcian blue staining showed a lack of the heterocyst envelope polysaccharide (Hep) layer. Northern blot and primer extension analyses showed that, in a manner dependent on the nitrogen-control transcription factor NtcA, all1711 was strongly induced after nitrogen step-down. Confocal microscopy of an Anabaena sp. strain producing an All1711-green fluorescent protein (All1711-GFP) fusion protein showed induction in all cells of the filament but at higher levels in differentiating heterocysts. All1711-GFP was located in the periphery of the cells, consistent with All1711 being a cytoplasmic membrane protein. Expression of all1711 from the P(glnA) promoter in a multicopy plasmid led to production of a presumptive exopolysaccharide by vegetative cells. These results suggest that All1711, which we denote HepP, is involved in transport of glycoside(s), with a specific physiological role in production of Hep.
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Tom SK, Callahan SM. The putative phosphatase All1758 is necessary for normal growth, cell size and synthesis of the minor heterocyst-specific glycolipid in the cyanobacterium Anabaena sp. strain PCC 7120. MICROBIOLOGY-SGM 2011; 158:380-389. [PMID: 22053007 DOI: 10.1099/mic.0.054783-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 differentiates nitrogen-fixing heterocysts arranged in a periodic pattern when deprived of a fixed source of nitrogen. In a genetic screen for mutations that prevent diazotrophic growth, open reading frame all1758, which encodes a putative serine/threonine phosphatase, was identified. Mutation of all1758 resulted in a number of seemingly disparate phenotypes that included a delay in the morphological differentiation of heterocysts, reduced cell size, and lethality under certain conditions. The mutant was incapable of fixing nitrogen under either oxic or anoxic conditions, and lacked the minor heterocyst-specific glycolipid. Pattern formation, as indicated by the timing and pattern of expression from the promoters of hetR and patS fused transcriptionally to the gene for green fluorescent protein (GFP), was unaffected by mutation of all1758, suggesting that its role in the formation of heterocysts is limited to morphological differentiation. Transcription of all1758 was constitutive with respect to both cell type and conditions of growth, but required a functional copy of all1758. The reduced cell size of the all1758 mutant and the location of all1758 between the cell division genes ftsX and ftsY may be indicative of a role for all1758 in cell division. Taken together, these results suggest that the protein encoded by all1758 may represent a link between cell growth, division and regulation of the morphological differentiation of heterocysts.
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Affiliation(s)
- Sasa K Tom
- Department of Microbiology, University of Hawaii, Honolulu, HI 96822, USA
| | - Sean M Callahan
- Department of Microbiology, University of Hawaii, Honolulu, HI 96822, USA
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Hfq is required for optimal nitrate assimilation in the Cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2011; 193:3546-55. [PMID: 21602329 DOI: 10.1128/jb.00254-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Hfq is an RNA binding protein involved in posttranscriptional regulation of gene expression in bacteria. It acts by binding to regulatory small RNAs (sRNAs), which confer specificity for the regulation. Recently, orthologues of the Hfq protein were annotated in cyanobacterial genomes, although its capacity to regulate gene expression by interacting with sRNAs has not been yet demonstrated. Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that, in the absence of combined nitrogen, is able to fix atmospheric nitrogen by differentiating specialized cells called heterocysts. We have generated an hfq knockout mutant of Anabaena sp. PCC 7120. Deletion of this gene results in differentiation of heterocysts in the presence of nitrate, suggesting a defect in nitrate assimilation. We show that hfq mutant cells are affected in transport and use of nitrate and nitrite. An analysis of the expression of several genes in the nir operon, encoding different elements of the nitrate assimilation pathway, demonstrates a downregulation of their transcription in mutant cells. We also observed that genes ntcB and cnaT, involved in the regulation of the nir operon, show a lower expression in cells lacking Hfq. Finally, when hfq was reintroduced in the mutant, heterocyst differentiation was no longer observed in the presence of nitrate. Therefore, our results indicate that the RNA chaperone Hfq is involved in the regulation of the nir operon, although the mechanism for this regulation is still unknown.
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González A, Bes MT, Peleato ML, Fillat MF. Unravelling the regulatory function of FurA in Anabaena sp. PCC 7120 through 2-D DIGE proteomic analysis. J Proteomics 2011; 74:660-71. [DOI: 10.1016/j.jprot.2011.02.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 01/25/2011] [Accepted: 02/02/2011] [Indexed: 01/19/2023]
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Bothe H, Schmitz O, Yates MG, Newton WE. Nitrogen fixation and hydrogen metabolism in cyanobacteria. Microbiol Mol Biol Rev 2010; 74:529-51. [PMID: 21119016 PMCID: PMC3008169 DOI: 10.1128/mmbr.00033-10] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N(2) fixation and/or H(2) formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H(2) as a source of combustible energy. To enhance the rates of H(2) production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H(2) formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.
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Affiliation(s)
- Hermann Bothe
- Botanical Institute, The University of Cologne, Zülpicher Str. 47b, D-50923 Cologne, Germany.
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The interplay between siderophore secretion and coupled iron and copper transport in the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2131-40. [DOI: 10.1016/j.bbamem.2010.07.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 07/05/2010] [Accepted: 07/13/2010] [Indexed: 11/20/2022]
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González A, Bes MT, Barja F, Peleato ML, Fillat MF. Overexpression of FurA in Anabaena sp. PCC 7120 Reveals New Targets for This Regulator Involved in Photosynthesis, Iron Uptake and Cellular Morphology. ACTA ACUST UNITED AC 2010; 51:1900-14. [DOI: 10.1093/pcp/pcq148] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Nicolaisen K, Hahn A, Schleiff E. The cell wall in heterocyst formation byAnabaenasp. PCC 7120. J Basic Microbiol 2009; 49:5-24. [DOI: 10.1002/jobm.200800300] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Role of two NtcA-binding sites in the complex ntcA gene promoter of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2008; 190:7584-90. [PMID: 18805988 DOI: 10.1128/jb.00856-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that fixes N(2) in specialized cells called heterocysts, which differentiate from vegetative cells in a process that requires the nitrogen control transcription factor NtcA. 2-Oxoglutarate-stimulated binding of purified NtcA to wild-type and modified versions of the ntcA gene promoter from Anabaena sp. was analyzed by mobility shift and DNase I footprinting assays, and the role of NtcA-binding sites in the expression of the ntcA gene during heterocyst differentiation was studied in vivo by using an ntcA-gfp translational fusion and primer extension analysis. Mutation of neither of the two identified NtcA-binding sites eliminated localized expression of ntcA in proheterocysts, but mutation of both sites led to very low, nonlocalized expression.
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Transcription activation by NtcA and 2-oxoglutarate of three genes involved in heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2008; 190:6126-33. [PMID: 18658268 DOI: 10.1128/jb.00787-08] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Anabaena sp. strain PCC 7120, differentiation of heterocysts takes place in response to the external cue of combined nitrogen deprivation, allowing the organism to fix atmospheric nitrogen in oxic environments. NtcA, a global transcriptional regulator of cyanobacteria, is required for activation of the expression of multiple genes involved in heterocyst differentiation, including key regulators that are specific to the process. We have set up a fully defined in vitro system, which includes the purified Anabaena RNA polymerase, and have studied the effects of NtcA and its signaling effector 2-oxoglutarate on RNA polymerase binding, open complex formation, and transcript production from promoters of the hetC, nrrA, and devB genes that are activated by NtcA at different stages of heterocyst differentiation. Both RNA polymerase and NtcA could specifically bind to the target DNA in the absence of any effector. 2-Oxoglutarate had a moderate positive effect on NtcA binding, and NtcA had a limited positive effect on RNA polymerase recruitment at the promoters. However, a stringent requirement of both NtcA and 2-oxoglutarate was observed for the detection of open complexes and transcript production at the three investigated promoters. These results support a key role for 2-oxoglutarate in transcription activation in the developing heterocyst.
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Cross-talk Between Iron and Nitrogen Regulatory Networks in Anabaena (Nostoc) sp. PCC 7120: Identification of Overlapping Genes in FurA and NtcA Regulons. J Mol Biol 2007; 374:267-81. [DOI: 10.1016/j.jmb.2007.09.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 08/30/2007] [Accepted: 09/04/2007] [Indexed: 01/26/2023]
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Moslavac S, Nicolaisen K, Mirus O, Al Dehni F, Pernil R, Flores E, Maldener I, Schleiff E. A TolC-like protein is required for heterocyst development in Anabaena sp. strain PCC 7120. J Bacteriol 2007; 189:7887-95. [PMID: 17720784 PMCID: PMC2168721 DOI: 10.1128/jb.00750-07] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 forms heterocysts in a semiregular pattern when it is grown on N2 as the sole nitrogen source. The transition from vegetative cells to heterocysts requires marked metabolic and morphological changes. We show that a trimeric pore-forming outer membrane beta-barrel protein belonging to the TolC family, Alr2887, is up-regulated in developing heterocysts and is essential for diazotrophic growth. Mutants defective in Alr2887 did not form the specific glycolipid layer of the heterocyst cell wall, which is necessary to protect nitrogenase from external oxygen. Comparison of the glycolipid contents of wild-type and mutant cells indicated that the protein is not involved in the synthesis of glycolipids but might instead serve as an exporter for the glycolipid moieties or enzymes involved in glycolipid attachment. We propose that Alr2887, together with an ABC transporter like DevBCA, is part of a protein export system essential for assembly of the heterocyst glycolipid layer. We designate the alr2887 gene hgdD (heterocyst glycolipid deposition protein).
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Affiliation(s)
- Suncana Moslavac
- LMU, Department of Biology I, VW-Research Group, Menzinger Str. 67, 80638 München, Germany
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Muro-Pastor AM, Olmedo-Verd E, Flores E. All4312, an NtcA-regulated two-component response regulator in Anabaena sp. strain PCC 7120. FEMS Microbiol Lett 2007; 256:171-7. [PMID: 16487336 DOI: 10.1111/j.1574-6968.2006.00136.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
All4312, encoded by open reading frame all4312 in the genome of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, exhibits a CheY-like receiver domain and an output domain similar to that of OmpR, characteristic of two-component response regulators. Expression of all4312 was directly regulated by NtcA, the global transcriptional regulator of nitrogen assimilation in cyanobacteria. Features characteristic of NtcA-activated promoters were also found upstream from genes encoding All4312 homologues in several other cyanobacterial genomes. Expression of all4312 was however unaffected in a mutant of hetR, which encodes a regulator triggering heterocyst development. The function of All4312 may be related to the cellular response to nitrogen deprivation.
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Affiliation(s)
- Alicia María Muro-Pastor
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Seville, Spain.
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Shi L, Li JH, Cheng Y, Wang L, Chen WL, Zhang CC. Two genes encoding protein kinases of the HstK family are involved in synthesis of the minor heterocyst-specific glycolipid in the cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2007; 189:5075-81. [PMID: 17513480 PMCID: PMC1951881 DOI: 10.1128/jb.00323-07] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N(2) under oxic conditions, and the activity of nitrogen fixation occurs exclusively in heterocysts, cells differentiated from vegetative cells in response to a limitation of a combined-nitrogen source in the growth medium. At the late stages of heterocyst differentiation, an envelope layer composed of two glycolipids is formed to limit the entry of oxygen so that the oxygen-sensitive nitrogenase can function. The genome of Anabaena sp. strain PCC 7120 possesses a family of 13 genes (the hstK family), all encoding proteins with a putative Ser/Thr kinase domain at their N termini and a His-kinase domain at their C termini. In this study, we showed that the double mutant D4.3 strain, in which two members of this gene family, pkn44 (all1625) and pkn30 (all3691), were both inactivated, failed to fix N(2) in the presence of oxygen (Fox(-)). In an environment without oxygen, a low level of nitrogenase activity was detectable (Fix(+)). Heterocyst development in the mutant D4.3 was delayed by 24 h and arrested at a relatively early stage without the formation of the glycolipid layer (Hgl(-)). Only the minor species of the two heterocyst-specific glycolipids (HGLs) was missing in the mutant. We propose that DevH, a putative transcription factor, coordinates the synthesis of both HGLs, while Pkn44/Pkn30 and the previously characterized PrpJ may represent two distinct regulatory pathways involved in the synthesis of the minor HGL and the major HGL, respectively.
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Affiliation(s)
- Lei Shi
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China
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Moslavac S, Reisinger V, Berg M, Mirus O, Vosyka O, Plöscher M, Flores E, Eichacker LA, Schleiff E. The proteome of the heterocyst cell wall in Anabaena sp. PCC 7120. Biol Chem 2007; 388:823-9. [PMID: 17655501 DOI: 10.1515/bc.2007.079] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Anabaena sp. PCC 7120 is a filamentous cyanobacterium that serves as a model to analyze prokaryotic cell differentiation, evolutionary development of plastids, and the regulation of nitrogen fixation. The cell wall is the cellular structure in contact with the surrounding medium. To understand the dynamics of the cell wall proteome during cell differentiation, the cell wall from Anabaena heterocysts was enriched and analyzed. In line with the recently proposed continuity of the outer membrane along the Anabaena filament, most of the proteins identified in the heterocyst cell-wall fraction are also present in the cell wall of vegetative cells, even though the lipid content of both membranes is different.
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Affiliation(s)
- Suncana Moslavac
- Department of Biology I, VW-Research Group, LMU Munich, Menzinger Str. 67, D-80638 München, Germany
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Ehira S, Ohmori M. NrrA, a nitrogen-responsive response regulator facilitates heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120. Mol Microbiol 2006; 59:1692-703. [PMID: 16553876 DOI: 10.1111/j.1365-2958.2006.05049.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The heterocyst is a specialized cell for nitrogen fixation in the filamentous cyanobacteria, and its development is triggered by limitation of combined nitrogen in the medium. During heterocyst development, patterns of gene expression change dramatically. We identified seven genes encoding transcriptional regulators that were upregulated by nitrogen deprivation in Anabaena PCC 7120, using an Anabaena oligonucleotide microarray. Among them, the nrrA gene, which encodes a response regulator of the OmpR family with a DNA-binding domain, has shown the most prominent induction after nitrogen deprivation. Expression of nrrA increased all through the filaments within 3 h of nitrogen deprivation and became higher in proheterocysts than in vegetative cells after 12 h. Sequence analysis of the promoter region of nrrA indicated that the induction of nrrA depended on NtcA, which is the global nitrogen regulator in cyanobacteria. In the nrrA deletion mutant, heterocyst development was delayed and the induction of hetR, which is the master gene in regulation of heterocyst development, was diminished up to 24 h nitrogen deprivation. It is concluded that nrrA facilitates heterocyst development.
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Affiliation(s)
- Shigeki Ehira
- Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Sakura, Japan
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Laurent S, Chen H, Bédu S, Ziarelli F, Peng L, Zhang CC. Nonmetabolizable analogue of 2-oxoglutarate elicits heterocyst differentiation under repressive conditions in Anabaena sp. PCC 7120. Proc Natl Acad Sci U S A 2005; 102:9907-12. [PMID: 15985552 PMCID: PMC1174989 DOI: 10.1073/pnas.0502337102] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In response to combined nitrogen starvation in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 is able to develop a particular cell type, called a heterocyst, specialized in molecular nitrogen fixation. Heterocysts are regularly intercalated among vegetative cells and represent 5-10% of all cells along each filament. In unicellular cyanobacteria, the key Krebs cycle intermediate, 2-oxoglutarate (2-OG), has been suggested as a nitrogen status signal, but in vivo evidence is still lacking. In this study we show that nitrogen starvation causes 2-OG to accumulate transiently within cells of Anabaena PCC 7120, reaching a maximal intracellular concentration of approximately 0.1 mM 1 h after combined nitrogen starvation. A nonmetabolizable fluorinated 2-OG derivative, 2,2-difluoropentanedioic acid (DFPA), was synthesized and used to demonstrate the signaling function of 2-OG in vivo. DFPA is shown to be a structural analogue of 2-OG and the process of its uptake and accumulation in vivo can be followed by (19)F magic angle spinning NMR because of the presence of the fluorine atom and its chemical stability. DFPA at a threshold concentration of 0.3 mM triggers heterocyst differentiation under repressing conditions. The multidisciplinary approaches using synthetic fluorinated analogues, magic angle spinning NMR for their analysis in vivo, and techniques of molecular biology provide a powerful means to identify the nature of the signals that remain unknown or poorly defined in many signaling pathways.
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Affiliation(s)
- Sophie Laurent
- Laboratoire de Chimie Bactérienne, UPR9043, Centre National de la Recherche Scientifique, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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