1
|
Pivato M, Grenzi M, Costa A, Ballottari M. Compartment-specific Ca 2+ imaging in the green alga Chlamydomonas reinhardtii reveals high light-induced chloroplast Ca 2+ signatures. THE NEW PHYTOLOGIST 2023; 240:258-271. [PMID: 37488718 DOI: 10.1111/nph.19142] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 06/26/2023] [Indexed: 07/26/2023]
Abstract
To investigate the role of intracellular Ca2+ signaling in the perception and response mechanisms to light in unicellular microalgae, the genetically encoded ratiometric Ca2+ indicator Yellow Cameleon (YC3.6) was expressed in the model organism for green algae Chlamydomonas reinhardtii, targeted to cytosol, chloroplast, and mitochondria. Through in vivo single-cell confocal microscopy imaging, light-induced Ca2+ signaling was investigated in different conditions and different genotypes, including the photoreceptors mutants phot and acry. A genetically encoded H2 O2 sensor was also adopted to investigate the possible role of H2 O2 formation in light-dependent Ca2+ signaling. Light-dependent Ca2+ response was observed in Chlamydomonas reinhardtii cells only in the chloroplast as an organelle-autonomous response, influenced by light intensity and photosynthetic electron transport. The absence of blue and red-light photoreceptor aCRY strongly reduced the light-dependent chloroplast Ca2+ response, while the absence of the blue photoreceptor PHOT had no significant effects. A correlation between high light-induced chloroplast H2 O2 gradients and Ca2+ transients was drawn, supported by H2 O2 -induced chloroplast Ca2+ transients in the dark. In conclusion, different triggers are involved in the light-induced chloroplast Ca2+ signaling as saturation of the photosynthetic electron transport, H2 O2 formation, and aCRY-dependent light perception.
Collapse
Affiliation(s)
- Matteo Pivato
- Department of Biotechnology, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
| | - Matteo Grenzi
- Department of Biosciences, University of Milan, Via Giovanni Celoria 26, 20133, Milan, Italy
| | - Alex Costa
- Department of Biosciences, University of Milan, Via Giovanni Celoria 26, 20133, Milan, Italy
- Institute of Biophysics, National Research Council of Italy (CNR), Milan, 20133, Italy
| | - Matteo Ballottari
- Department of Biotechnology, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
| |
Collapse
|
2
|
Cecchin M, Simicevic J, Chaput L, Hernandez Gil M, Girolomoni L, Cazzaniga S, Remacle C, Hoeng J, Ivanov NV, Titz B, Ballottari M. Acclimation strategies of the green alga Chlorella vulgaris to different light regimes revealed by physiological and comparative proteomic analyses. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:4540-4558. [PMID: 37155956 DOI: 10.1093/jxb/erad170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/05/2023] [Indexed: 05/10/2023]
Abstract
Acclimation to different light regimes is at the basis of survival for photosynthetic organisms, regardless of their evolutionary origin. Previous research efforts largely focused on acclimation events occurring at the level of the photosynthetic apparatus and often highlighted species-specific mechanisms. Here, we investigated the consequences of acclimation to different irradiances in Chlorella vulgaris, a green alga that is one of the most promising species for industrial application, focusing on both photosynthetic and mitochondrial activities. Moreover, proteomic analysis of cells acclimated to high light (HL) or low light (LL) allowed identification of the main targets of acclimation in terms of differentially expressed proteins. The results obtained demonstrate photosynthetic adaptation to HL versus LL that was only partially consistent with previous findings in Chlamydomonas reinhardtii, a model organism for green algae, but in many cases similar to vascular plant acclimation events. Increased mitochondrial respiration measured in HL-acclimated cells mainly relied on alternative oxidative pathway dissipating the excessive reducing power produced due to enhanced carbon flow. Finally, proteins involved in cell metabolism, intracellular transport, gene expression, and signaling-including a heliorhodopsin homolog-were identified as strongly differentially expressed in HL versus LL, suggesting their key roles in acclimation to different light regimes.
Collapse
Affiliation(s)
- Michela Cecchin
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Jovan Simicevic
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Louise Chaput
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Manuel Hernandez Gil
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Laura Girolomoni
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Stefano Cazzaniga
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Claire Remacle
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium
| | - Julia Hoeng
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Nikolai V Ivanov
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Bjoern Titz
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, 2000 Neuchâtel, Switzerland
| | - Matteo Ballottari
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| |
Collapse
|
3
|
Cecchin M, Paloschi M, Busnardo G, Cazzaniga S, Cuine S, Li‐Beisson Y, Wobbe L, Ballottari M. CO 2 supply modulates lipid remodelling, photosynthetic and respiratory activities in Chlorella species. PLANT, CELL & ENVIRONMENT 2021; 44:2987-3001. [PMID: 33931891 PMCID: PMC8453743 DOI: 10.1111/pce.14074] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 04/20/2021] [Accepted: 04/23/2021] [Indexed: 05/28/2023]
Abstract
Microalgae represent a potential solution to reduce CO2 emission exploiting their photosynthetic activity. Here, the physiologic and metabolic responses at the base of CO2 assimilation were investigated in conditions of high or low CO2 availability in two of the most promising algae species for industrial cultivation, Chlorella sorokiniana and Chlorella vulgaris. In both species, high CO2 availability increased biomass accumulation with specific increase of triacylglycerols in C. vulgaris and polar lipids and proteins in C. sorokiniana. Moreover, high CO2 availability caused only in C. vulgaris a reduced NAD(P)H/NADP+ ratio and reduced mitochondrial respiration, suggesting a CO2 dependent increase of reducing power consumption in the chloroplast, which in turn influences the redox state of the mitochondria. Several rearrangements of the photosynthetic machinery were observed in both species, differing from those described for the model organism Chlamydomonas reinhardtii, where adaptation to carbon availability is mainly controlled by the translational repressor NAB1. NAB1 homologous protein could be identified only in C. vulgaris but lacked the regulation mechanisms previously described in C. reinhardtii. Acclimation strategies to cope with a fluctuating inorganic carbon supply are thus diverse among green microalgae, and these results suggest new biotechnological strategies to boost CO2 fixation.
Collapse
Affiliation(s)
- Michela Cecchin
- Dipartimento di BiotecnologieUniversità di VeronaVeronaItaly
| | - Matteo Paloschi
- Dipartimento di BiotecnologieUniversità di VeronaVeronaItaly
| | | | | | - Stephan Cuine
- Aix‐Marseille Univ., CEA, CNRSInstitute of Biosciences and Biotechnologies of Aix‐Marseille, UMR7265, CEA CadaracheSaint‐Paul‐lez DuranceFrance
| | - Yonghua Li‐Beisson
- Aix‐Marseille Univ., CEA, CNRSInstitute of Biosciences and Biotechnologies of Aix‐Marseille, UMR7265, CEA CadaracheSaint‐Paul‐lez DuranceFrance
| | - Lutz Wobbe
- Bielefeld UniversityCenter for Biotechnology (CeBiTec), Faculty of BiologyBielefeldGermany
| | | |
Collapse
|
4
|
Pan-transcriptome identifying master genes and regulation network in response to drought and salt stresses in Alfalfa (Medicago sativa L.). Sci Rep 2021; 11:17203. [PMID: 34446782 PMCID: PMC8390513 DOI: 10.1038/s41598-021-96712-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 08/10/2021] [Indexed: 02/07/2023] Open
Abstract
Alfalfa is an important legume forage grown worldwide and its productivity is affected by environmental stresses such as drought and high salinity. In this work, three alfalfa germplasms with contrasting tolerances to drought and high salinity were used for unraveling the transcriptomic responses to drought and salt stresses. Twenty-one different RNA samples from different germplasm, stress conditions or tissue sources (leaf, stem and root) were extracted and sequenced using the PacBio (Iso-Seq) and the Illumina platforms to obtain full-length transcriptomic profiles. A total of 1,124,275 and 91,378 unique isoforms and genes were obtained, respectively. Comparative analysis of transcriptomes identified differentially expressed genes and isoforms as well as transcriptional and post-transcriptional modifications such as alternative splicing events, fusion genes and nonsense-mediated mRNA decay events and non-coding RNA such as circRNA and lncRNA. This is the first time to identify the diversity of circRNA and lncRNA in response to drought and high salinity in alfalfa. The analysis of weighted gene co-expression network allowed to identify master genes and isoforms that may play important roles on drought and salt stress tolerance in alfalfa. This work provides insight for understanding the mechanisms by which drought and salt stresses affect alfalfa growth at the whole genome level.
Collapse
|
5
|
Wobbe L. The Molecular Function of Plant mTERFs as Key Regulators of Organellar Gene Expression. PLANT & CELL PHYSIOLOGY 2021; 61:2004-2017. [PMID: 33067620 DOI: 10.1093/pcp/pcaa132] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/25/2020] [Indexed: 05/27/2023]
Abstract
The protein family of mTERFs (mitochondrial transcription termination factors) was initially studied in mammalian and insect mitochondria before the first Arabidopsis mTERF mutant was characterized. More than 10 years of research on the function of plant mTERFs in the flowering plants Arabidopsis thaliana, Zea mays and the green microalga Chlamydomonas reinhardtii has since highlighted that mTERFs are key regulators of organellar gene expression (OGE) in mitochondria and in chloroplasts. Additional functions to be fulfilled by plant mTERFs (e.g. splicing) and the fact that the expression of two organellar genomes had to be facilitated have led to a massive expansion of the plant mTERF portfolio compared to that found in mammals. Plant mTERFs are implicated in all steps of OGE ranging from the modulation of transcription to the maturation of tRNAs and hence translation. Furthermore, being regulators of OGE, mTERFs are required for a successful long-term acclimation to abiotic stress, retrograde signaling and interorganellar communication. Here, I review the recent progress in the elucidation of molecular mTERF functions.
Collapse
Affiliation(s)
- Lutz Wobbe
- Algae Biotechnology & Bioenergy Group, Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld University, Universit�tsstrasse 27, Bielefeld 33615, Germany
| |
Collapse
|
6
|
A fluorescence-based approach to screen for productive chemically mutagenized strains of Desmodesmus armatus. ALGAL RES 2020. [DOI: 10.1016/j.algal.2020.102028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
7
|
Distinct roles of alternative oxidase pathway during the greening process of etiolated algae. SCIENCE CHINA-LIFE SCIENCES 2020; 64:816-827. [PMID: 32712832 DOI: 10.1007/s11427-020-1755-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 05/09/2020] [Indexed: 12/19/2022]
Abstract
The vital function of mitochondrial alternative oxidase (AOX) pathway in optimizing photosynthesis during plant de-etiolation has been well recognized. However, whether and how AOX impacts the chloroplast biogenesis in algal cells remains unclear. In the present study, the role of AOX in regulating the reassembly of chloroplast in algal cells was investigated by treating Auxenochlorella protothecoides with salicylhydroxamic acid (SHAM), the specific inhibitor to AOX, in the heterotrophy to autotrophy transition process. Several lines of evidences including delayed chlorophyll accumulation, lagged reorganization of chloroplast structure, altered PSI/PSII stoichiometry, and declined photosynthetic activities in SHAM treated cells indicated that the impairment in AOX activity dramatically hindered the development of functioning chloroplast in algal cells. Besides, the cellular ROS levels and activities of antioxidant enzymes were increased by SHAM treatment, and the perturbation on the balance of NAD+/NADH and NADP+/NADPH ratios was also observed in A. protothecoides lacking AOX activity, indicating that AOX was essential in promoting ROS scavenging and keeping the redox homeostasis for algal chloroplast development during greening. Overall, our study revealed the essentiality of mitochondrial AOX pathway in sustaining algal photosynthetic performance and provided novel insights into the physiological roles of AOX on the biogenesis of photosynthetic organelle in algae.
Collapse
|
8
|
Burlacot A, Peltier G, Li-Beisson Y. Subcellular Energetics and Carbon Storage in Chlamydomonas. Cells 2019; 8:E1154. [PMID: 31561610 PMCID: PMC6830334 DOI: 10.3390/cells8101154] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 09/19/2019] [Accepted: 09/24/2019] [Indexed: 01/09/2023] Open
Abstract
Microalgae have emerged as a promising platform for production of carbon- and energy- rich molecules, notably starch and oil. Establishing an economically viable algal biotechnology sector requires a holistic understanding of algal photosynthesis, physiology, cell cycle and metabolism. Starch/oil productivity is a combined effect of their cellular content and cell division activities. Cell growth, starch and fatty acid synthesis all require carbon building blocks and a source of energy in the form of ATP and NADPH, but with a different requirement in ATP/NADPH ratio. Thus, several cellular mechanisms have been developed by microalgae to balance ATP and NADPH supply which are essentially produced by photosynthesis. Major energy management mechanisms include ATP production by the chloroplast-based cyclic electron flow and NADPH removal by water-water cycles. Furthermore, energetic coupling between chloroplast and other cellular compartments, mitochondria and peroxisome, is increasingly recognized as an important process involved in the chloroplast redox poise. Emerging literature suggests that alterations of energy management pathways affect not only cell fitness and survival, but also influence biomass content and composition. These emerging discoveries are important steps towards diverting algal photosynthetic energy to useful products for biotechnological applications.
Collapse
Affiliation(s)
- Adrien Burlacot
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
| | - Gilles Peltier
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
| |
Collapse
|
9
|
Kaye Y, Huang W, Clowez S, Saroussi S, Idoine A, Sanz-Luque E, Grossman AR. The mitochondrial alternative oxidase from Chlamydomonas reinhardtii enables survival in high light. J Biol Chem 2018; 294:1380-1395. [PMID: 30510139 DOI: 10.1074/jbc.ra118.004667] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/24/2018] [Indexed: 01/07/2023] Open
Abstract
Photosynthetic organisms often experience extreme light conditions that can cause hyper-reduction of the chloroplast electron transport chain, resulting in oxidative damage. Accumulating evidence suggests that mitochondrial respiration and chloroplast photosynthesis are coupled when cells are absorbing high levels of excitation energy. This coupling helps protect the cells from hyper-reduction of photosynthetic electron carriers and diminishes the production of reactive oxygen species (ROS). To examine this cooperative protection, here we characterized Chlamydomonas reinhardtii mutants lacking the mitochondrial alternative terminal respiratory oxidases, CrAOX1 and CrAOX2. Using fluorescent fusion proteins, we experimentally demonstrated that both enzymes localize to mitochondria. We also observed that the mutant strains were more sensitive than WT cells to high light under mixotrophic and photoautotrophic conditions, with the aox1 strain being more sensitive than aox2 Additionally, the lack of CrAOX1 increased ROS accumulation, especially in very high light, and damaged the photosynthetic machinery, ultimately resulting in cell death. These findings indicate that the Chlamydomonas AOX proteins can participate in acclimation of C. reinhardtii cells to excess absorbed light energy. They suggest that when photosynthetic electron carriers are highly reduced, a chloroplast-mitochondria coupling allows safe dissipation of photosynthetically derived electrons via the reduction of O2 through AOX (especially AOX1)-dependent mitochondrial respiration.
Collapse
Affiliation(s)
- Yuval Kaye
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305.
| | - Weichao Huang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Sophie Clowez
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Shai Saroussi
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Adam Idoine
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Emanuel Sanz-Luque
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| |
Collapse
|
10
|
Shevtsov S, Nevo-Dinur K, Faigon L, Sultan LD, Zmudjak M, Markovits M, Ostersetzer-Biran O. Control of organelle gene expression by the mitochondrial transcription termination factor mTERF22 in Arabidopsis thaliana plants. PLoS One 2018; 13:e0201631. [PMID: 30059532 PMCID: PMC6066234 DOI: 10.1371/journal.pone.0201631] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 07/18/2018] [Indexed: 11/28/2022] Open
Abstract
Mitochondria are key sites for cellular energy metabolism and are essential to cell survival. As descendants of eubacterial symbionts (specifically α-proteobacteria), mitochondria contain their own genomes (mtDNAs), RNAs and ribosomes. Plants need to coordinate their energy demands during particular growth and developmental stages. The regulation of mtDNA expression is critical for controlling the oxidative phosphorylation capacity in response to physiological or environmental signals. The mitochondrial transcription termination factor (mTERF) family has recently emerged as a central player in mitochondrial gene expression in various eukaryotes. Interestingly, the number of mTERFs has been greatly expanded in the nuclear genomes of plants, with more than 30 members in different angiosperms. The majority of the annotated mTERFs in plants are predicted to be plastid- or mitochondria-localized. These are therefore expected to play important roles in organellar gene expression in angiosperms. Yet, functions have been assigned to only a small fraction of these factors in plants. Here, we report the characterization of mTERF22 (At5g64950) which functions in the regulation of mtDNA transcription in Arabidopsis thaliana. GFP localization assays indicate that mTERF22 resides within the mitochondria. Disruption of mTERF22 function results in reduced mtRNA accumulation and altered organelle biogenesis. Transcriptomic and run-on experiments suggest that the phenotypes of mterf22 mutants are attributable, at least in part, to altered mitochondria transcription, and indicate that mTERF22 affects the expression of numerous mitochondrial genes in Arabidopsis plants.
Collapse
Affiliation(s)
- Sofia Shevtsov
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Keren Nevo-Dinur
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Lior Faigon
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Laure D. Sultan
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Michal Zmudjak
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Mark Markovits
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
| | - Oren Ostersetzer-Biran
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, Israel
- * E-mail:
| |
Collapse
|
11
|
Molecular basis of autotrophic vs mixotrophic growth in Chlorella sorokiniana. Sci Rep 2018; 8:6465. [PMID: 29691462 PMCID: PMC5915390 DOI: 10.1038/s41598-018-24979-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 04/13/2018] [Indexed: 11/24/2022] Open
Abstract
In this work, we investigated the molecular basis of autotrophic vs. mixotrophic growth of Chlorella sorokiniana, one of the most productive microalgae species with high potential to produce biofuels, food and high value compounds. To increase biomass accumulation, photosynthetic microalgae are commonly cultivated in mixotrophic conditions, adding reduced carbon sources to the growth media. In the case of C. sorokiniana, the presence of acetate enhanced biomass, proteins, lipids and starch productivity when compared to autotrophic conditions. Despite decreased chlorophyll content, photosynthetic properties were essentially unaffected while differential gene expression profile revealed transcriptional regulation of several genes mainly involved in control of carbon flux. Interestingly, acetate assimilation caused upregulation of phosphoenolpyruvate carboxylase enzyme, enabling potential recovery of carbon atoms lost by acetate oxidation. The obtained results allowed to associate the increased productivity observed in mixotrophy in C. sorokiniana with a different gene regulation leading to a fine regulation of cell metabolism.
Collapse
|
12
|
Venkanna D, Südfeld C, Baier T, Homburg SV, Patel AV, Wobbe L, Kruse O. Knock-Down of the IFR1 Protein Perturbs the Homeostasis of Reactive Electrophile Species and Boosts Photosynthetic Hydrogen Production in Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2017; 8:1347. [PMID: 28824682 PMCID: PMC5540887 DOI: 10.3389/fpls.2017.01347] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 07/19/2017] [Indexed: 05/26/2023]
Abstract
The protein superfamily of short-chain dehydrogenases/reductases (SDR), including members of the atypical type (aSDR), covers a huge range of catalyzed reactions and in vivo substrates. This superfamily also comprises isoflavone reductase-like (IRL) proteins, which are aSDRs highly homologous to isoflavone reductases from leguminous plants. The molecular function of IRLs in non-leguminous plants and green microalgae has not been identified as yet, but several lines of evidence point at their implication in reactive oxygen species homeostasis. The Chlamydomonas reinhardtii IRL protein IFR1 was identified in a previous study, analyzing the transcriptomic changes occurring during the acclimation to sulfur deprivation and anaerobiosis, a condition that triggers photobiological hydrogen production in this microalgae. Accumulation of the cytosolic IFR1 protein is induced by sulfur limitation as well as by the exposure of C. reinhardtii cells to reactive electrophile species (RES) such as reactive carbonyls. The latter has not been described for IRL proteins before. Over-accumulation of IFR1 in the singlet oxygen response 1 (sor1) mutant together with the presence of an electrophile response element, known to be required for SOR1-dependent gene activation as a response to RES, in the promoter of IFR1, indicate that IFR1 expression is controlled by the SOR1-dependent pathway. An implication of IFR1 into RES homeostasis, is further implied by a knock-down of IFR1, which results in a diminished tolerance toward RES. Intriguingly, IFR1 knock-down has a positive effect on photosystem II (PSII) stability under sulfur-deprived conditions used to trigger photobiological hydrogen production, by reducing PSII-dependent oxygen evolution, in C. reinhardtii. Reduced PSII photoinhibition in IFR1 knock-down strains prolongs the hydrogen production phase resulting in an almost doubled final hydrogen yield compared to the parental strain. Finally, IFR1 knock-down could be successfully used to further increase hydrogen yields of the high hydrogen-producing mutant stm6, demonstrating that IFR1 is a promising target for genetic engineering approaches aiming at an increased hydrogen production capacity of C. reinhardtii cells.
Collapse
Affiliation(s)
- Deepak Venkanna
- Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld UniversityBielefeld, Germany
| | - Christian Südfeld
- Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld UniversityBielefeld, Germany
| | - Thomas Baier
- Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld UniversityBielefeld, Germany
| | - Sarah V. Homburg
- Faculty of Engineering and Mathematics, Fermentation and Formulation of Biologicals and Chemicals, Bielefeld University of Applied SciencesBielefeld, Germany
| | - Anant V. Patel
- Faculty of Engineering and Mathematics, Fermentation and Formulation of Biologicals and Chemicals, Bielefeld University of Applied SciencesBielefeld, Germany
| | - Lutz Wobbe
- Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld UniversityBielefeld, Germany
| | - Olaf Kruse
- Faculty of Biology, Center for Biotechnology (CeBiTec), Bielefeld UniversityBielefeld, Germany
| |
Collapse
|