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Norena-Caro DA, Zuniga C, Pete AJ, Saemundsson SA, Donaldson MR, Adams AJ, Dooley KM, Zengler K, Benton MG. Analysis of the cyanobacterial amino acid metabolism with a precise genome-scale metabolic reconstruction of Anabaena sp. UTEX 2576. Biochem Eng J 2021. [DOI: 10.1016/j.bej.2021.108008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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2
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Eichner M, Basu S, Gledhill M, de Beer D, Shaked Y. Hydrogen Dynamics in Trichodesmium Colonies and Their Potential Role in Mineral Iron Acquisition. Front Microbiol 2019; 10:1565. [PMID: 31354665 PMCID: PMC6636555 DOI: 10.3389/fmicb.2019.01565] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 06/24/2019] [Indexed: 12/14/2022] Open
Abstract
N2-fixing cyanobacteria mediate H2 fluxes through the opposing processes of H2 evolution, which is a by-product of the N2 fixation reaction, and H2 uptake, which is driven by uptake hydrogenases. Here, we used microelectrodes to characterize H2 and O2 dynamics in single natural colonies of the globally important N2 fixer Trichodesmium collected from the Gulf of Eilat. We observed gradually changing H2 dynamics over the course of the day, including both net H2 evolution and net H2 uptake, as well as large differences in H2 fluxes between individual colonies. Net H2 uptake was observed in colonies amended with H2 in both light and dark. Net H2 evolution was recorded in the light only, reflecting light-dependent N2 fixation coupled to H2 evolution. Both net H2 evolution and H2 uptake rates were higher before 2 pm than later in the day. These pronounced H2 dynamics in the morning coincided with strong net O2 uptake and the previously reported diel peak in N2 fixation. Later in the afternoon, when photosynthesis rates determined by O2 measurements were highest, and N2 fixation rates decrease according to previous studies, the H2 dynamics were also less pronounced. Thus, the observed diel variations in H2 dynamics reflect diel changes in the rates of O2 consumption and N2 fixation. Remarkably, the presence of H2 strongly stimulated the uptake of mineral iron by natural colonies. The magnitude of this effect was dependent on the time of day, with the strongest response in incubations that started before 2 pm, i.e., the period that covered the time of highest uptake hydrogenase activity. Based on these findings, we propose that by providing an electron source for mineral iron reduction in N2-fixing cells, H2 may contribute to iron uptake in Trichodesmium colonies.
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Affiliation(s)
- Meri Eichner
- Microsensor Group, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Subhajit Basu
- The Freddy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- The Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel
| | - Martha Gledhill
- GEOMAR Helmholtz Center for Ocean Research Kiel, Kiel, Germany
| | - Dirk de Beer
- Microsensor Group, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Yeala Shaked
- The Freddy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- The Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel
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3
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Mueller TJ, Welsh EA, Pakrasi HB, Maranas CD. Identifying Regulatory Changes to Facilitate Nitrogen Fixation in the Nondiazotroph Synechocystis sp. PCC 6803. ACS Synth Biol 2016; 5:250-8. [PMID: 26692191 DOI: 10.1021/acssynbio.5b00202] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The incorporation of biological nitrogen fixation into a nondiazotrophic photosynthetic organism provides a promising solution to the increasing fixed nitrogen demand, but is accompanied by a number of challenges for accommodating two incompatible processes within the same organism. Here we present regulatory influence networks for two cyanobacteria, Synechocystis PCC 6803 and Cyanothece ATCC 51142, and evaluate them to co-opt native transcription factors that may be used to control the nif gene cluster once it is transferred to Synechocystis. These networks were further examined to identify candidate transcription factors for other metabolic processes necessary for temporal separation of photosynthesis and nitrogen fixation, glycogen catabolism and cyanophycin synthesis. Two transcription factors native to Synechocystis, LexA and Rcp1, were identified as promising candidates for the control of the nif gene cluster and other pertinent metabolic processes, respectively. Lessons learned in the incorporation of nitrogen fixation into a nondiazotrophic prokaryote may be leveraged to further progress the incorporation of nitrogen fixation in plants.
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Affiliation(s)
- Thomas J. Mueller
- Department
of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, United States
| | - Eric A. Welsh
- Cancer
Informatics Core, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Himadri B. Pakrasi
- Department
of Energy, Environmental, and Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States
- Department
of Biology, Washington University, St. Louis, Missouri 63130, United States
| | - Costas D. Maranas
- Department
of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, United States
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Vaishampayan A, Sinha RP, Häder DP. Use of Genetically Improved Nitrogen-Fixing Cyanobacteria in Rice Paddy Fields: Prospects as a Source Material for Engineering Herbicide Sensitivity and Resistance in Plants. ACTA ACUST UNITED AC 2014. [DOI: 10.1111/j.1438-8677.1998.tb00693.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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5
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Lau NS, Foong CP, Kurihara Y, Sudesh K, Matsui M. RNA-Seq analysis provides insights for understanding photoautotrophic polyhydroxyalkanoate production in recombinant Synechocystis Sp. PLoS One 2014; 9:e86368. [PMID: 24466058 PMCID: PMC3899235 DOI: 10.1371/journal.pone.0086368] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/06/2013] [Indexed: 11/18/2022] Open
Abstract
The photosynthetic cyanobacterium, Synechocystis sp. strain 6803, is a potential platform for the production of various chemicals and biofuels. In this study, direct photosynthetic production of a biopolymer, polyhydroxyalkanoate (PHA), in genetically engineered Synechocystis sp. achieved as high as 14 wt%. This is the highest production reported in Synechocystis sp. under photoautotrophic cultivation conditions without the addition of a carbon source. The addition of acetate increased PHA accumulation to 41 wt%, and this value is comparable to the highest production obtained with cyanobacteria. Transcriptome analysis by RNA-seq coupled with real-time PCR was performed to understand the global changes in transcript levels of cells subjected to conditions suitable for photoautotrophic PHA biosynthesis. There was lower expression of most PHA synthesis-related genes in recombinant Synechocystis sp. with higher PHA accumulation suggesting that the concentration of these enzymes is not the limiting factor to achieving high PHA accumulation. In order to cope with the higher PHA production, cells may utilize enhanced photosynthesis to drive the product formation. Results from this study suggest that the total flux of carbon is the possible driving force for the biosynthesis of PHA and the polymerizing enzyme, PHA synthase, is not the only critical factor affecting PHA-synthesis. Knowledge of the regulation or control points of the biopolymer production pathways will facilitate the further use of cyanobacteria for biotechnological applications.
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Affiliation(s)
- Nyok-Sean Lau
- Ecobiomaterial Research Laboratory, School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia
- Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Choon Pin Foong
- Ecobiomaterial Research Laboratory, School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia
- Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Yukio Kurihara
- Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Kumar Sudesh
- Ecobiomaterial Research Laboratory, School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia
- * E-mail: (KS); (MM)
| | - Minami Matsui
- Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
- * E-mail: (KS); (MM)
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6
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Gaudana SB, Krishnakumar S, Alagesan S, Digmurti MG, Viswanathan GA, Chetty M, Wangikar PP. Rhythmic and sustained oscillations in metabolism and gene expression of Cyanothece sp. ATCC 51142 under constant light. Front Microbiol 2013; 4:374. [PMID: 24367360 PMCID: PMC3854555 DOI: 10.3389/fmicb.2013.00374] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 11/21/2013] [Indexed: 11/13/2022] Open
Abstract
Cyanobacteria, a group of photosynthetic prokaryotes, oscillate between day and night time metabolisms with concomitant oscillations in gene expression in response to light/dark cycles (LD). The oscillations in gene expression have been shown to sustain in constant light (LL) with a free running period of 24 h in a model cyanobacterium Synechococcus elongatus PCC 7942. However, equivalent oscillations in metabolism are not reported under LL in this non-nitrogen fixing cyanobacterium. Here we focus on Cyanothece sp. ATCC 51142, a unicellular, nitrogen-fixing cyanobacterium known to temporally separate the processes of oxygenic photosynthesis and oxygen-sensitive nitrogen fixation. In a recent report, metabolism of Cyanothece 51142 has been shown to oscillate between photosynthetic and respiratory phases under LL with free running periods that are temperature dependent but significantly shorter than the circadian period. Further, the oscillations shift to circadian pattern at moderate cell densities that are concomitant with slower growth rates. Here we take this understanding forward and demonstrate that the ultradian rhythm under LL sustains at much higher cell densities when grown under turbulent regimes that simulate flashing light effect. Our results suggest that the ultradian rhythm in metabolism may be needed to support higher carbon and nitrogen requirements of rapidly growing cells under LL. With a comprehensive Real time PCR based gene expression analysis we account for key regulatory interactions and demonstrate the interplay between clock genes and the genes of key metabolic pathways. Further, we observe that several genes that peak at dusk in Synechococcus peak at dawn in Cyanothece and vice versa. The circadian rhythm of this organism appears to be more robust with peaking of genes in anticipation of the ensuing photosynthetic and respiratory metabolic phases.
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Affiliation(s)
- Sandeep B Gaudana
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
| | - S Krishnakumar
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
| | - Swathi Alagesan
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
| | - Madhuri G Digmurti
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
| | - Ganesh A Viswanathan
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
| | - Madhu Chetty
- Gippsland School of Information Technology, Monash University VIC, Australia
| | - Pramod P Wangikar
- Department of Chemical Engineering, Indian Institute of Technology Bombay Powai, Mumbai, India
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Post AF, Rihtman B, Wang Q. Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101. THE ISME JOURNAL 2012; 6:629-37. [PMID: 21938021 PMCID: PMC3280139 DOI: 10.1038/ismej.2011.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 08/03/2011] [Accepted: 08/03/2011] [Indexed: 11/09/2022]
Abstract
Nitrogen (N) physiology in the marine cyanobacterium Trichodesmium IMS101 was studied along with transcript accumulation of the N-regulatory gene ntcA and of two of its target genes: napA (nitrate assimilation) and nifH (N(2) fixation). N(2) fixation was impaired in the presence of nitrite, nitrate and urea. Strain IMS101 was capable of growth on these combined N sources at <2 μM but growth rates declined at elevated concentrations. Assimilation of nitrate and urea was impaired in the presence of ammonium. Whereas ecologically relevant N concentrations (2-20 μM) suppressed growth and assimilation, much higher concentrations were required to affect transcript levels. Transcripts of nifH accumulated under nitrogen-fixing conditions; these transcript levels were maintained in the presence of nitrate (100 μM) and ammonium (20 μM). However, nifH transcript levels were below detection at ammonium concentrations >20 μM. napA mRNA was found at low levels in both N(2)-fixing and ammonium-utilizing filaments, and it accumulated in filaments grown with nitrate. The positive effect of nitrate on napA transcription was abolished by ammonium additions of >200 μM. This effect was restored upon addition of the glutamine synthetase inhibitor L-methionin-DL-sulfoximine. Surprisingly, ntcA transcript levels remained high in the presence of ammonium, even at elevated concentrations. These findings indicate that ammonium repression is decoupled from transcriptional activation of ntcA in Trichodesmium IMS101.
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Affiliation(s)
- Anton F Post
- The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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8
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Chen Y, Holtman CK, Taton A, Golden SS. Functional Analysis of the Synechococcus elongatus PCC 7942 Genome. FUNCTIONAL GENOMICS AND EVOLUTION OF PHOTOSYNTHETIC SYSTEMS 2012. [DOI: 10.1007/978-94-007-1533-2_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Verma A, Nain V, Kumari C, Singh SK, Lakshmi Narasu M, Ananda Kumar P. Tissue specific response of Agrobacterium tumefaciens attachment to Sorghum bicolor (L) Moench. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2008; 14:307-313. [PMID: 23572896 PMCID: PMC3550632 DOI: 10.1007/s12298-008-0028-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Agrobacterium mediated genetic transformation of plants have advantages over other methods, especially for making single copy transgenic plants with reduced chances of gene silencing and instability. However, monocotyledonous plant species could not utilize the full potential of this system because of possible limitations in Agrobacterium interaction with monocot plant cells. Agrobacterium attachment as a factor in genetic transformation was studied in the leaf, shoot apex, and leaf derived callus of sorghum (Sorghum bicolor (L) Moench). Pre-induction of Agrobacterium with acetosyringone was found necessary for Agrobacterium attachment to sorghum tissues. All the explants responded positively, with preferential Agrobacterium attachment and colonization around the tissues having actively dividing cells. Callus proved to be the best explant for Agrobacterium attachment as observed in scanning electron microscopy and transient GUS expression. Loss of Agrobacterium attachment was observed with an increase in the degree of tissue differentiation.
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Affiliation(s)
- Anju Verma
- />National Research Centre on Plant Biotechnology, IARI, New Delhi, 110012 India
| | - Vikrant Nain
- />National Research Centre on Plant Biotechnology, IARI, New Delhi, 110012 India
| | - Chetana Kumari
- />National Research Centre on Plant Biotechnology, IARI, New Delhi, 110012 India
| | - Santosh Kumar Singh
- />National Research Centre on Plant Biotechnology, IARI, New Delhi, 110012 India
| | - M. Lakshmi Narasu
- />School of Biotechnology, Institute of Post Graduate Studies and Research, Jawaharlal Nehru Technological University, Hyderabad, 500028 India
| | - P. Ananda Kumar
- />National Research Centre on Plant Biotechnology, IARI, New Delhi, 110012 India
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10
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Differential transcriptional analysis of the cyanobacterium Cyanothece sp. strain ATCC 51142 during light-dark and continuous-light growth. J Bacteriol 2008; 190:3904-13. [PMID: 18390663 DOI: 10.1128/jb.00206-08] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We analyzed the metabolic rhythms and differential gene expression in the unicellular, diazotrophic cyanobacterium Cyanothece sp. strain ATCC 51142 under N(2)-fixing conditions after a shift from normal 12-h light-12-h dark cycles to continuous light. We found that the mRNA levels of approximately 10% of the genes in the genome demonstrated circadian behavior during growth in free-running (continuous light) conditions. The genes for N(2) fixation displayed a strong circadian behavior, whereas photosynthesis and respiration genes were not as tightly regulated. One of our main objectives was to determine the strategies used by these cells to perform N(2) fixation under normal day-night conditions, as well as under the greater stress caused by continuous light. We determined that N(2) fixation cycled in continuous light but with a lower N(2) fixation activity. Glycogen degradation, respiration, and photosynthesis were also lower; nonetheless, O(2) evolution was about 50% of the normal peak. We also demonstrated that nifH (encoding the nitrogenase Fe protein), nifB, and nifX were strongly induced in continuous light; this is consistent with the role of these proteins during the assembly of the enzyme complex and suggested that the decreased N(2) fixation activity was due to protein-level regulation or inhibition. Many soluble electron carriers (e.g., ferredoxins), as well as redox carriers (e.g., thioredoxin and glutathione), were strongly induced during N(2) fixation in continuous light. We suggest that these carriers are required to enhance cyclic electron transport and phosphorylation for energy production and to maintain appropriate redox levels in the presence of elevated O(2), respectively.
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11
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Kannan N, Wu J, Anand GS, Yooseph S, Neuwald AF, Venter JC, Taylor SS. Evolution of allostery in the cyclic nucleotide binding module. Genome Biol 2008; 8:R264. [PMID: 18076763 PMCID: PMC2246266 DOI: 10.1186/gb-2007-8-12-r264] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Revised: 11/18/2007] [Accepted: 12/12/2007] [Indexed: 11/10/2022] Open
Abstract
Analysis of cyclic nucleotide binding (CNB) domains shows that they have evolved to sense a wide variety of second messenger signals; a mechanism for allosteric regulation by CNB domains is proposed. Background The cyclic nucleotide binding (CNB) domain regulates signaling pathways in both eukaryotes and prokaryotes. In this study, we analyze the evolutionary information embedded in genomic sequences to explore the diversity of signaling through the CNB domain and also how the CNB domain elicits a cellular response upon binding to cAMP. Results Identification and classification of CNB domains in Global Ocean Sampling and other protein sequences reveals that they typically are fused to a wide variety of functional domains. CNB domains have undergone major sequence variation during evolution. In particular, the sequence motif that anchors the cAMP phosphate (termed the PBC motif) is strikingly different in some families. This variation may contribute to ligand specificity inasmuch as members of the prokaryotic cooA family, for example, harbor a CNB domain that contains a non-canonical PBC motif and that binds a heme ligand in the cAMP binding pocket. Statistical comparison of the functional constraints imposed on the canonical and non-canonical PBC containing sequences reveals that a key arginine, which coordinates with the cAMP phosphate, has co-evolved with a glycine in a distal β2-β3 loop that allosterically couples cAMP binding to distal regulatory sites. Conclusion Our analysis suggests that CNB domains have evolved as a scaffold to sense a wide variety of second messenger signals. Based on sequence, structural and biochemical data, we propose a mechanism for allosteric regulation by CNB domains.
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Affiliation(s)
- Natarajan Kannan
- Department of Chemistry and Biochemistry, University of California, Gilman Drive, La Jolla, California 92093-0654, USA
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12
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De Castro C, Gargiulo V, Lanzetta R, Parrilli M. Agrobacterium rubi(T) DSM 6772 produces a lipophilic polysaccharide capsule whose degree of acetylation is growth modulated. Biomacromolecules 2007; 8:1047-51. [PMID: 17284069 DOI: 10.1021/bm061081f] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structure of the capsular polysaccharide produced from the type strain of Agrobacterium rubi DSM 6772 is demonstrated by means of chemical and spectroscopical methodologies. It is constituted from the quite rare monosaccharide 6-deoxy-L-talose, involved in alternating alpha-(1 --> 2) and alpha-(1 --> 3) linkages. This simple backbone is further complicated from the occurrence of O-acetyl substituents located always at O-2 of the O-3 substituted 6-deoxy-talose. This decoration is not stoichiometric and it depends on the growth stadium of the bacterium, leading to an almost regular acetylation pattern only at the stationary phase, where all the potential positions are substituted.
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Affiliation(s)
- Cristina De Castro
- Department of Organic Chemistry and Biochemistry, University of Naples, Complesso Universitario Monte Sant' Angelo, Via Cintia 4, 80126 Napoli, Italy.
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Mori S, Castoreno A, Lammers PJ. Transcript levels of rbcR1, ntcA, and rbcL/S genes in cyanobacterium Anabaena sp. PCC 7120 are downregulated in response to cold and osmotic stress. FEMS Microbiol Lett 2002; 213:167-73. [PMID: 12167533 DOI: 10.1111/j.1574-6968.2002.tb11301.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Using differential display, we identified the Anabaena sp. PCC 7120 ribulose 1,5-bisphosphate carboxylase transcriptional regulator (rbcR1) gene, a member of the LysR family of positive transcription factors. The rbcR1 transcript and its putative target gene ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL/S) were repressed by cold (20 degrees C) and osmotic (sucrose and salt) stress. Cold stress also induced a transient downregulation of the Anabaena 7120 ntcA transcriptional regulator. Expression of the ntcA gene, however, returned to normal levels 2 h after initiation of cold stress and increased significantly above normal levels 24 h after growth at 20 degrees C. The early decline in the expression of the ntcA, rbcR1, and rbcL/S transcripts appears to be part of the Anabaena 7120 global adaptation response to stress. The substantial increase in the ntcA gene expression 24 h following cold stress suggests that Anabaena 7120 experiences substantial nitrogen limitation under these conditions. These data suggest that in response to stress, Anabaena 7120 decreases its metabolic activity through regulation of the CO(2) fixation machinery while enhancing its nitrogen assimilation by inducing the expression of the nitrogen global transcriptional regulator, NtcA.
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Affiliation(s)
- Shahram Mori
- Department of Chemistry and Biochemistry, Box 3C, New Mexico State University, Las Cruces 88003, USA.
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Alfonso M, Perewoska I, Kirilovsky D. Redox control of ntcA gene expression in Synechocystis sp. PCC 6803. Nitrogen availability and electron transport regulate the levels of the NtcA protein. PLANT PHYSIOLOGY 2001; 125:969-981. [PMID: 11161053 PMCID: PMC64897 DOI: 10.1104/pp.125.2.969] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2000] [Revised: 08/16/2000] [Accepted: 10/16/2000] [Indexed: 05/23/2023]
Abstract
In this work we have studied the influence of the cellular redox status in the expression of the Synechocystis sp. PCC 6803 ntcA gene. Two different ntcA transcripts with different 5' ends were detected, depending on the different dark/light or nitrogen availability conditions. Accumulation of a 0.8-kb ntcA message was light and nitrogen dependent, whereas a longer 1.2-kb ntcA transcript was neither light nor nitrogen regulated. NtcA protein levels increased concomitantly with the accumulation of the 0.8-kb ntcA transcript. The light-dependent accumulation of the ntcA gene and the NtcA protein was sensitive to electron transport inhibitors. In addition, Glc-grown Synechocystis sp. cells showed a similar ntcA expression pattern in darkness to that observed under illumination. These data suggested that electron transport, and not light per se may regulate ntcA gene expression. Primer extension analysis, together with gel mobility-shift assays, demonstrated that in vitro, the Synechocystis sp. NtcA protein specifically bound to the putative promoter region from the light/nitrogen-dependent ntcA transcript but not to that from the constitutive 1.2-kb ntcA mRNA. Band-shift experiments carried out in the presence of thiol oxidizing/modifiying agents and different reducing/oxidizing conditions suggested that NtcA binding to its own promoter was under a thiol-dependent redox mechanism. Our results suggest that the cellular redox status plays a central role in the autoregulatory mechanism of the NtcA protein.
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Affiliation(s)
- M Alfonso
- Unité Mixte de Recherche, 8543 Photorégulation et Dynamique des Membranes Végetales, Centre National de la Recherche Scientifique, Ecole Normale Supériéure, 46 rue d'Ulm, 75230 Paris cedex 05, France.
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15
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Affiliation(s)
- A Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, E-41092 Seville, Spain
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16
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Mori T, Johnson CH. Circadian control of cell division in unicellular organisms. PROGRESS IN CELL CYCLE RESEARCH 2000; 4:185-92. [PMID: 10740825 DOI: 10.1007/978-1-4615-4253-7_16] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Cell division cycles and circadian rhythms are major periodic phenomena in organisms. Circadian oscillators control biochemical, physiological, and behavioral events in a wide range of living systems including almost all eukaryotes that have been tested and some prokaryotes-in particular, the cyanobacteria. Gating of cell division is one of the key processes that has been reported to be regulated by circadian clocks in many organisms. We survey studies of the circadian control of cell division in eukaryotic microorganisms and introduce recent progress on understanding the interaction between circadian rhythms and cell division cycles in cyanobacteria.
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Affiliation(s)
- T Mori
- Department of Biology, Vanderbilt University, Nashville, TN 37235, USA
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17
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Lee HM, Vázquez-Bermúdez MF, de Marsac NT. The global nitrogen regulator NtcA regulates transcription of the signal transducer PII (GlnB) and influences its phosphorylation level in response to nitrogen and carbon supplies in the Cyanobacterium synechococcus sp. strain PCC 7942. J Bacteriol 1999; 181:2697-702. [PMID: 10217756 PMCID: PMC93707 DOI: 10.1128/jb.181.9.2697-2702.1999] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The PII protein is encoded by a unique glnB gene in Synechococcus sp. strain PCC 7942. Its expression has been analyzed in the wild type and in NtcA-null mutant cells grown under different conditions of nitrogen and carbon supply. RNA-DNA hybridization experiments revealed the presence of one transcript species 680 nucleotides long, whatever the nutrient conditions tested. A second transcript species, 620 nucleotides long, absent in the NtcA null mutant, was observed in wild-type cells that were nitrogen starved for 2 h under both high and low CO2 and in the presence of nitrate under a high CO2 concentration. Primer extension analysis indicated that the two transcript species are generated from two tandem promoters, a sigma70 Escherichia coli-type promoter and an NtcA-dependent promoter, located 120 and 53 nucleotides, respectively, from the glnB initiation codon. The NtcA-dependent promoter is up-regulated under the conditions mentioned above, while the sigma70 E. coli-type promoter displays constitutive levels of transcripts in the NtcA null mutant and slightly different levels in the wild-type cells, depending on the nitrogen and carbon supplies. In general, a good correlation between the amounts of the two transcript species and that of the PII protein was observed, as revealed by immunodetection with specific antibodies. The phosphorylation level of PII in the wild type is inversely correlated with nitrogen availability and directly correlated with higher CO2 concentration. This regulation is correspondingly less stringent in the NtcA null mutant cells. In contrast, the dephosphorylation of PII is NtcA independent.
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Affiliation(s)
- H M Lee
- Département de Biochimie et Génétique Moléculaire, Unité de Physiologie Microbienne, Institut Pasteur, 75724 Paris Cedex 15, France
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Dominic B, Chen YB, Zehr JP. Cloning and transcriptional analysis of the nifUHDK genes of Trichodesmium sp. IMS101 reveals stable nifD, nifDK and nifK transcripts. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 12):3359-3368. [PMID: 9884228 DOI: 10.1099/00221287-144-12-3359] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Trichodesmium spp. are marine filamentous, non-heterocystous cyanobacteria capable of aerobic nitrogen fixation. In this study, the nitrogenase structural genes (nifHDK) and nifU gene of Trichodesmium sp. IMS101 were cloned and sequenced. The Trichodesmium sp. IMS101 nifH, nifD and nifK amino acid sequences showed only 79%, 66% and 68% identity, respectively, to those of Anabaena sp. strain PCC 7120. A potential transcription start site for nifH was found 212 bases upstream of the nifH start codon. Promoter-like nucleotide sequences upstream of the transcription start site were identified that were very similar to those identified for the nitrogenase genes of Anabaena spp. Sequence analysis revealed regions of DNA that may form stem-loop structures in the intercistronic regions downstream of nifH and nifD. RNA analysis by Northern hybridization revealed the presence of transcripts corresponding to nifH, nifHD and nifHDK. Surprisingly, Northern hybridization also revealed the presence of transcripts that corresponded to nifD, nifDK and nifK, which have not been previously reported as transcripts in contiguous nifHDK genes of cyanobacteria. Transcription of the nifHDK genes was not significantly repressed in the presence of nitrate at a final concentration of 20 mM or at oxygen concentrations of up to 40%, whereas ammonium and urea inhibited nifHDK transcription. The transcription of the nifHDK genes was not affected by darkness, which suggests that transcription of these genes in Trichodesmium is not directly regulated by light.
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Lindell D, Padan E, Post AF. Regulation of ntcA expression and nitrite uptake in the marine Synechococcus sp. strain WH 7803. J Bacteriol 1998; 180:1878-86. [PMID: 9537388 PMCID: PMC107103 DOI: 10.1128/jb.180.7.1878-1886.1998] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/1997] [Accepted: 01/20/1998] [Indexed: 02/07/2023] Open
Abstract
NtcA is a transcriptional activator involved in global nitrogen control in cyanobacteria. In the absence of ammonium it regulates the transcription of a series of genes encoding proteins required for the uptake and assimilation of alternative nitrogen sources (I. Luque, E. Flores, and A. Herrero, EMBO J. 13:2862-2869, 1994). ntcA, present in a single copy in the marine Synechococcus sp. strain WH 7803, was cloned and sequenced. The putative amino acid sequence shows a high degree of identity to NtcA from freshwater cyanobacteria in two functional domains. The expression of ntcA was negatively regulated by ammonium from a putative transcription start point located downstream of an NtcA consensus recognition sequence. Addition of either rifampin or ammonium led to a rapid decline in ntcA transcript levels with half-lives of less than 2 min in both cases. Nitrate-grown cells showed high ntcA transcript levels, as well as the capacity for active nitrite uptake. However, ammonium-grown cells showed low levels of the ntcA transcript and did not utilize nitrite. The addition of ammonium to nitrite uptake-active cells resulted in a gradual decline in the rate of uptake over a 24-h period. Active nitrite uptake was not induced in cells transferred to medium lacking a nitrogen source despite evidence of elevated expression of ntcA, indicating that ntcA expression is not sufficient for uptake capacity to develop. Nitrate and nitrite addition led to the development of nitrite uptake, whereas the addition of leucine did not. Furthermore, nitrite addition triggered the de novo protein synthesis required for uptake capacity to develop. These data suggest that nitrite and nitrate act as specific inducers for the synthesis of proteins required for nitrite uptake.
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Affiliation(s)
- D Lindell
- H. Steinitz Marine Biology Laboratory, Interuniversity Institute for Marine Sciences, Eilat, Israel
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