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Berthold M, Campbell DA. Restoration, conservation and phytoplankton hysteresis. Conserv Physiol 2021; 9:coab062. [PMID: 34394942 PMCID: PMC8361504 DOI: 10.1093/conphys/coab062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 06/10/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
Phytoplankton growth depends not only upon external factors that are not strongly altered by the presence of phytoplankton, such as temperature, but also upon factors that are strongly influenced by activity of phytoplankton, including photosynthetically active radiation, and the availability of the macronutrients carbon, nitrogen, phosphorus and, for some, silicate. Since phytoplankton therefore modify, and to an extent create, their own habitats, established phytoplankton communities can show resistance and resilience to change, including managed changes in nutrient regimes. Phytoplankton blooms and community structures can be predicted from the overall biogeochemical setting and inputs, but restorations may be influenced by the physiological responses of established phytoplankton taxa to nutrient inputs, temperature, second-order changes in illumination and nutrient recycling. In this review we discuss the contributions of phytoplankton ecophysiology to biogeochemical hysteresis and possible effects on community composition in the face of management, conservation or remediation plans.
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Affiliation(s)
- Maximilian Berthold
- Department of Biology, Mount Allison University, Sackville, New Brunswick E4L 1C9, Canada
| | - Douglas A Campbell
- Department of Biology, Mount Allison University, Sackville, New Brunswick E4L 1C9, Canada
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Weiss TL, Young EJ, Ducat DC. A synthetic, light-driven consortium of cyanobacteria and heterotrophic bacteria enables stable polyhydroxybutyrate production. Metab Eng 2017; 44:236-245. [DOI: 10.1016/j.ymben.2017.10.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/28/2017] [Accepted: 10/16/2017] [Indexed: 10/18/2022]
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Rochaix JD, Ramundo S. Conditional repression of essential chloroplast genes: Evidence for new plastid signaling pathways. Biochim Biophys Acta 2014; 1847:986-92. [PMID: 25486627 DOI: 10.1016/j.bbabio.2014.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 11/26/2014] [Indexed: 01/28/2023]
Abstract
The development of a repressible chloroplast gene expression system in Chlamydomonas reinhardtii has opened the door for studying the role of essential chloroplast genes. This approach has been used to analyze three chloroplast genes of this sort coding for the α subunit of RNA polymerase (rpoA), a ribosomal protein (rps12) and the catalytic subunit of the ATP-dependent ClpP protease (clpP1). Depletion of the three corresponding proteins leads to growth arrest and cell death. Shutdown of chloroplast transcription and translation increases the abundance of a set of plastid transcripts that includes mainly those involved in transcription, translation and proteolysis and reveals multiple regulatory feedback loops in the chloroplast gene circuitry. Depletion of ClpP profoundly affects plastid protein homeostasis and elicits an autophagy-like response with extensive cytoplasmic vacuolization of cells. It also triggers changes in chloroplast and nuclear gene expression resulting in increased abundance of chaperones, proteases, ubiquitin-related proteins and proteins involved in lipid trafficking and thylakoid biogenesis. These features are hallmarks of an unfolded protein response in the chloroplast and raise new questions on plastid protein homeostasis and plastid signaling. This article is part of a Special Issue entitled: Chloroplast Biogenesis.
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Affiliation(s)
- Jean-David Rochaix
- Department of Molecular Biology, University of Geneva, 1211 Geneva, Switzerland; Department of Plant Biology, University of Geneva, 1211 Geneva, Switzerland.
| | - Silvia Ramundo
- Department of Molecular Biology, University of Geneva, 1211 Geneva, Switzerland; Department of Plant Biology, University of Geneva, 1211 Geneva, Switzerland
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Ramundo S, Casero D, Mühlhaus T, Hemme D, Sommer F, Crèvecoeur M, Rahire M, Schroda M, Rusch J, Goodenough U, Pellegrini M, Perez-Perez ME, Crespo JL, Schaad O, Civic N, Rochaix JD. Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control. Plant Cell 2014; 26:2201-2222. [PMID: 24879428 PMCID: PMC4079378 DOI: 10.1105/tpc.114.124842] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 04/16/2014] [Accepted: 05/09/2014] [Indexed: 05/14/2023]
Abstract
Plastid protein homeostasis is critical during chloroplast biogenesis and responses to changes in environmental conditions. Proteases and molecular chaperones involved in plastid protein quality control are encoded by the nucleus except for the catalytic subunit of ClpP, an evolutionarily conserved serine protease. Unlike its Escherichia coli ortholog, this chloroplast protease is essential for cell viability. To study its function, we used a recently developed system of repressible chloroplast gene expression in the alga Chlamydomonas reinhardtii. Using this repressible system, we have shown that a selective gradual depletion of ClpP leads to alteration of chloroplast morphology, causes formation of vesicles, and induces extensive cytoplasmic vacuolization that is reminiscent of autophagy. Analysis of the transcriptome and proteome during ClpP depletion revealed a set of proteins that are more abundant at the protein level, but not at the RNA level. These proteins may comprise some of the ClpP substrates. Moreover, the specific increase in accumulation, both at the RNA and protein level, of small heat shock proteins, chaperones, proteases, and proteins involved in thylakoid maintenance upon perturbation of plastid protein homeostasis suggests the existence of a chloroplast-to-nucleus signaling pathway involved in organelle quality control. We suggest that this represents a chloroplast unfolded protein response that is conceptually similar to that observed in the endoplasmic reticulum and in mitochondria.
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Affiliation(s)
- Silvia Ramundo
- Departments of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - David Casero
- Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095
| | - Timo Mühlhaus
- Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm Germany
| | - Dorothea Hemme
- Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm Germany
| | - Frederik Sommer
- Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm Germany
| | - Michèle Crèvecoeur
- Departments of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Michèle Rahire
- Departments of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Michael Schroda
- Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm Germany
| | - Jannette Rusch
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Ursula Goodenough
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Matteo Pellegrini
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, California 90095
| | - Maria Esther Perez-Perez
- Instituto de Bioquimica Vegetal y Fotosintesis, Consejo Superior de Investigaciones Cientificas, Universidad de Sevilla, 41092 Sevilla, Spain
| | - José Luis Crespo
- Instituto de Bioquimica Vegetal y Fotosintesis, Consejo Superior de Investigaciones Cientificas, Universidad de Sevilla, 41092 Sevilla, Spain
| | - Olivier Schaad
- Genomics Platform, University of Geneva, 1211 Geneva, Switzerland Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
| | - Natacha Civic
- Genomics Platform, University of Geneva, 1211 Geneva, Switzerland
| | - Jean David Rochaix
- Departments of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
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Ludwig M, Bryant DA. Acclimation of the Global Transcriptome of the Cyanobacterium Synechococcus sp. Strain PCC 7002 to Nutrient Limitations and Different Nitrogen Sources. Front Microbiol 2012; 3:145. [PMID: 22514553 PMCID: PMC3323872 DOI: 10.3389/fmicb.2012.00145] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 03/26/2012] [Indexed: 11/29/2022] Open
Abstract
The unicellular, euryhaline cyanobacterium Synechococcus sp. strain PCC 7002 is a model organism for laboratory-based studies of cyanobacterial metabolism and is a potential platform for biotechnological applications. Two of its most notable properties are its exceptional tolerance of high-light intensity and very rapid growth under optimal conditions. In this study, transcription profiling by RNAseq has been used to perform an integrated study of global changes in transcript levels in cells subjected to limitation for the major nutrients CO2, nitrogen, sulfate, phosphate, and iron. Transcriptional patterns for cells grown on nitrate, ammonia, and urea were also studied. Nutrient limitation caused strong decreases of transcript levels of the genes encoding major metabolic pathways, especially for components of the photosynthetic apparatus, CO2 fixation, and protein biosynthesis. Uptake mechanisms for the respective nutrients were strongly up-regulated. The transcription data further suggest that major changes in the composition of the NADH dehydrogenase complex occur upon nutrient limitation. Transcripts for flavoproteins increased strongly when CO2 was limiting. Genes involved in protection from oxidative stress generally showed high, constitutive transcript levels, which possibly explains the high-light tolerance of this organism. The transcriptomes of cells grown with ammonia or urea as nitrogen source showed increased transcript levels for components of the CO2 fixation machinery compared to cells grown with nitrate, but in general transcription differences in cells grown on different N-sources exhibited surprisingly minor differences.
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Affiliation(s)
- Marcus Ludwig
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University University Park, PA, USA
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Olinares PDB, Kim J, van Wijk KJ. The Clp protease system; a central component of the chloroplast protease network. Biochim Biophys Acta 2010; 1807:999-1011. [PMID: 21167127 DOI: 10.1016/j.bbabio.2010.12.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 11/30/2010] [Accepted: 12/03/2010] [Indexed: 10/18/2022]
Abstract
Intra-plastid proteases play crucial and diverse roles in the development and maintenance of non-photosynthetic plastids and chloroplasts. Formation and maintenance of a functional thylakoid electron transport chain requires various protease activities, operating in parallel, as well as in series. This review first provides a short, referenced overview of all experimentally identified plastid proteases in Arabidopsis thaliana. We then focus on the Clp protease system which constitutes the most abundant and complex soluble protease system in the plastid, consisting of 15 nuclear-encoded members and one plastid-encoded member in Arabidopsis. Comparisons to the simpler Clp system in photosynthetic and non-photosynthetic bacteria will be made and the role of Clp proteases in the green algae Chlamydomonas reinhardtii will be briefly reviewed. Extensive molecular genetics has shown that the Clp system plays an essential role in Arabidopsis chloroplast development in the embryo as well as in leaves. Molecular characterization of the various Clp mutants has elucidated many of the consequences of loss of Clp activities. We summarize and discuss the structural and functional aspects of the Clp machinery, including progress on substrate identification and recognition. Finally, the Clp system will be evaluated in the context of the chloroplast protease network. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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Abstract
Calcite nucleation on the surface of cyanobacteria of the Synechococcus leopoliensis strain PCC 7942 was investigated to assess the influence of photosynthetic uptake of inorganic carbon and active ion exchange processes across the cell membrane on the nucleation and precipitation mechanisms. We performed long-term precipitation experiments at a constant CO(2) level in ambient air by adding suspensions of previously washed cyanobacteria to solutions of NaHCO(3)/CaCl(2) which were supersaturated with respect to calcite. Induction times between 4 and 110 h were measured over a range of saturation states, Omega, between 8 and 4. The kinetics of CaCO(3) nucleation was compared between experiments: (i) with ongoing photosynthesis, (ii) with cells metabolizing but not undergoing photosynthetic uptake of inorganic carbon and (iii) in darkness without photosynthesis. No significant differences were observed between the three treatments. The results reveal that under low nutrient concentrations and permanent CO(2) supply, photosynthetic uptake of inorganic carbon predominantly uses CO(2) and consequently does not directly influence the nucleation process of CaCO(3) at the surface of S. leopoliensis. Furthermore, ion exchange processes did not affect the kinetics, indicating a passive nucleation process wherein the cell surface or extracellular polymers provided preferential sites for mineral nucleation. The catalyzing effect of the cyanobacteria on calcite nucleation was equivalent to a approximately 18% reduction in the specific interfacial free energy of the calcite nuclei. This result and the ubiquitous abundance of cyanobacteria suggest that this process may have an impact on local and global carbon cycling.
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Affiliation(s)
- M Obst
- Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland.
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Rudella A, Friso G, Alonso JM, Ecker JR, van Wijk KJ. Downregulation of ClpR2 leads to reduced accumulation of the ClpPRS protease complex and defects in chloroplast biogenesis in Arabidopsis. Plant Cell 2006; 18:1704-21. [PMID: 16766689 PMCID: PMC1488914 DOI: 10.1105/tpc.106.042861] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Plastids contain tetradecameric Clp protease core complexes, with five ClpP Ser-type proteases, four nonproteolytic ClpR, and two associated ClpS proteins. Accumulation of total ClpPRS complex decreased twofold to threefold in an Arabidopsis thaliana T-DNA insertion mutant in CLPR2 designated clpr2-1. Differential stable isotope labeling of the ClpPRS complex with iTRAQ revealed a fivefold reduction in assembled ClpR2 accumulation and twofold to fivefold reductions in the other subunits. A ClpR2:(his)(6) fusion protein that incorporated into the chloroplast ClpPRS complex fully complemented clpr2-1. The reduced accumulation of the ClpPRS protease complex led to a pale-green phenotype with delayed shoot development, smaller chloroplasts, decreased thylakoid accumulation, and increased plastoglobule accumulation. Stromal ClpC1 and 2 were both recruited to the thylakoid surface in clpr2-1. The thylakoid membrane of clpr2-1 showed increased carotenoid content, partial inactivation of photosystem II, and upregulated thylakoid proteases and stromal chaperones, suggesting an imbalance in chloroplast protein homeostasis and a well-coordinated network of proteolysis and chaperone activities. Interestingly, a subpopulation of PsaF and several light-harvesting complex II proteins accumulated in the thylakoid with unprocessed chloroplast transit peptides. We conclude that ClpR2 cannot be functionally replaced by other ClpP/R homologues and that the ClpPRS complex is central to chloroplast biogenesis, thylakoid protein homeostasis, and plant development.
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Affiliation(s)
- Andrea Rudella
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
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Adam Z, Rudella A, van Wijk KJ. Recent advances in the study of Clp, FtsH and other proteases located in chloroplasts. Curr Opin Plant Biol 2006; 9:234-40. [PMID: 16603408 DOI: 10.1016/j.pbi.2006.03.010] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Accepted: 03/22/2006] [Indexed: 05/08/2023]
Abstract
Several chloroplast proteases have been characterized in recent years. The ATP-dependent chloroplast proteases Clp and FtsH stand out because they form multi-subunit complexes consisting of different gene products. Surprisingly, both green and non-green plastids appear to contain a similar soluble Clp core proteolytic complex, consisting of five ClpP proteases, their non-catalytic ClpR homologs, and two ClpS homologs that have unknown function. Analyses of single and double FtsH1, FtsH2, FtsH5 and FtsH8 mutants, and overexpression of FtsH proteins in these Arabidopsis thaliana mutants show partial redundancies within pairs of closely related FtsH thylakoid proteins. The presence of at least one member of each pair is essential for functional accumulation. Other chloroplast proteases have also been identified recently. Future challenges include the identification of substrate recognition mechanisms and elucidating the role of proteases in chloroplast biogenesis and function.
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Affiliation(s)
- Zach Adam
- Institute of Plant Sciences and Genetics, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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Schwarz R, Forchhammer K. Acclimation of unicellular cyanobacteria to macronutrient deficiency: emergence of a complex network of cellular responses. Microbiology (Reading) 2005; 151:2503-2514. [PMID: 16079330 DOI: 10.1099/mic.0.27883-0] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cyanobacteria are equipped with numerous mechanisms that allow them to survive under conditions of nutrient starvation, some of which are unique to these organisms. This review surveys the molecular mechanisms underlying acclimation responses to nitrogen and phosphorus deprivation, with an emphasis on non-diazotrophic freshwater cyanobacteria. As documented for other micro-organisms, nutrient limitation of cyanobacteria elicits both general and specific responses. The general responses occur under any starvation condition and are the result of the stresses imposed by arrested anabolism. In contrast, the specific responses are acclimation processes that occur as a result of limitation for a particular nutrient; they lead to modification of metabolic and physiological routes to compensate for the restriction. First, the general acclimation processes are discussed, with an emphasis on modifications of the photosynthetic apparatus. The molecular mechanisms underlying specific responses to phosphorus and nitrogen-limitation are then outlined, and finally the cross-talk between pathways modulating specific and general responses is described.
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Affiliation(s)
- Rakefet Schwarz
- Faculty of Life Sciences, Bar-Ilan University, 52900 Ramat-Gan, Israel
| | - Karl Forchhammer
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Giessen, 35392 Giessen, Germany
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