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Barták M, Hájek J, Orekhova A, Villagra J, Marín C, Palfner G, Casanova-Katny A. Inhibition of Primary Photosynthesis in Desiccating Antarctic Lichens Differing in Their Photobionts, Thallus Morphology, and Spectral Properties. Microorganisms 2021; 9:microorganisms9040818. [PMID: 33924436 PMCID: PMC8070113 DOI: 10.3390/microorganisms9040818] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/02/2021] [Accepted: 04/07/2021] [Indexed: 11/16/2022] Open
Abstract
Five macrolichens of different thallus morphology from Antarctica (King George Island) were used for this ecophysiological study. The effect of thallus desiccation on primary photosynthetic processes was examined. We investigated the lichens' responses to the relative water content (RWC) in their thalli during the transition from a wet (RWC of 100%) to a dry state (RWC of 0%). The slow Kautsky kinetics of chlorophyll fluorescence (ChlF) that was recorded during controlled dehydration (RWC decreased from 100 to 0%) and supplemented with a quenching analysis revealed a polyphasic species-specific response of variable fluorescence. The changes in ChlF at a steady state (Fs), potential and effective quantum yields of photosystem II (FV/FM, ΦPSII), and nonphotochemical quenching (NPQ) reflected a desiccation-induced inhibition of the photosynthetic processes. The dehydration-dependent fall in FV/FM and ΦPSII was species-specific, starting at an RWC range of 22-32%. The critical RWC for ΦPSII was below 5%. The changes indicated the involvement of protective mechanisms in the chloroplastic apparatus of lichen photobionts at RWCs of below 20%. In both the wet and dry states, the spectral reflectance curves (SRC) (wavelength 400-800 nm) and indices (NDVI, PRI) of the studied lichen species were measured. Black Himantormia lugubris showed no difference in the SRCs between wet and dry state. Other lichens showed a higher reflectance in the dry state compared to the wet state. The lichen morphology and anatomy data, together with the ChlF and spectral reflectance data, are discussed in relation to its potential for ecophysiological studies in Antarctic lichens.
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Affiliation(s)
- Miloš Barták
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, Building A13/119, 625 00 Brno, Czech Republic; (M.B.); (J.H.); (A.O.)
| | - Josef Hájek
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, Building A13/119, 625 00 Brno, Czech Republic; (M.B.); (J.H.); (A.O.)
| | - Alla Orekhova
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, Building A13/119, 625 00 Brno, Czech Republic; (M.B.); (J.H.); (A.O.)
| | - Johana Villagra
- Laboratory of Plant Ecophysiology, Faculty of Natural Resources, Campus Luis Rivas del Canto, Catholic University of Temuco, Rudecindo Ortega #03694, 4780000 Temuco, Chile;
| | - Catalina Marín
- Laboratory of Mycology and Mycorrhiza, Faculty of Natural Sciences and Oceanography, Campus Concepción, Concepción University, 4030000 Concepción, Chile; (C.M.); (G.P.)
| | - Götz Palfner
- Laboratory of Mycology and Mycorrhiza, Faculty of Natural Sciences and Oceanography, Campus Concepción, Concepción University, 4030000 Concepción, Chile; (C.M.); (G.P.)
| | - Angélica Casanova-Katny
- Laboratory of Plant Ecophysiology, Faculty of Natural Resources, Campus Luis Rivas del Canto, Catholic University of Temuco, Rudecindo Ortega #03694, 4780000 Temuco, Chile;
- Correspondence: ; Tel.: +56-96-209-7709
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Phinney NH, Solhaug KA, Gauslaa Y. Photobiont-dependent humidity threshold for chlorolichen photosystem II activation. PLANTA 2019; 250:2023-2031. [PMID: 31542811 DOI: 10.1007/s00425-019-03282-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 09/13/2019] [Indexed: 05/05/2023]
Abstract
Photobiont type influences the relative humidity threshold at which photosystem II activates in green algal lichens. Water vapor uptake alone can activate photosynthesis in lichens with green algal photobionts. However, the minimum relative humidity needed for activation is insufficiently known. The objective of this study was to quantify the humidity threshold for photosystem II (PSII) activation in a range of chlorolichen species associated with photobionts from Trebouxiaceae, Coccomyxaceae and Trentepohliaceae. These lichens exhibit distribution, habitat and substrate patterns that are likely coupled to their efficiency in utilizing water vapor at lower levels of relative humidity (RH) for photosynthesis. Using chlorophyll fluorescence imaging during water uptake from humid air of 25 species of chlorolichens representing the above photobiont groups, we monitored PSII activation within controlled chambers with constant RH at five levels ranging from 75.6 to 95.4%. The results demonstrate clear photobiont-specific activation patterns: the trentepohlioid lichens activated PSII at significantly lower RH (75.6%) than trebouxioid (81.7%) and coccomyxoid (92.0%) lichens. These responses are consistent with a preference for warm and sheltered habitats for trentepohlioid lichens, with cool and moist habitats for the coccomyxoid lichens, and with a more widespread occurrence of the trebouxioid lichens. Within each photobiont group, lichen species exposed to marine aerosols in their source habitats seemed to be activated at lower RH than lichens sampled from inland sites. High osmolyte concentration may therefore play a role in lowering a photobiont's activation threshold. We conclude that photobiont type influences water vapor-driven photosynthetic activation of lichens, thereby shaping the ecological niches in which they occur.
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Affiliation(s)
- Nathan H Phinney
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway.
| | - Knut Asbjørn Solhaug
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway
| | - Yngvar Gauslaa
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway
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Backhaus T, Meeßen J, Demets R, de Vera JP, Ott S. Characterization of Viability of the Lichen Buellia frigida After 1.5 Years in Space on the International Space Station. ASTROBIOLOGY 2019; 19:233-241. [PMID: 30742495 DOI: 10.1089/ast.2018.1894] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The lichen Buellia frigida was exposed to space and simulated Mars analog conditions in the Biology and Mars Experiment (BIOMEX) project operated outside the International Space Station (ISS) for 1.5 years. To determine the effects of the Low Earth Orbit (LEO) conditions on the lichen symbionts, a LIVE/DEAD staining analysis test was performed. After return from the ISS, the lichen symbionts demonstrated mortality rates of up to 100% for the algal symbiont and up to 97.8% for the fungal symbiont. In contrast, the lichen symbiont controls exhibited mortality rates of 10.3% up to 31.9% for the algal symbiont and 14.5% for the fungal symbiont. The results performed in the BIOMEX Mars simulation experiment on the ISS indicate that the potential for survival and the resistance of the lichen B. frigida to LEO conditions are very low. It is unlikely that Mars could be inhabited by this lichen, even for a limited amount of time, or even not habitable planet for the tested lichen symbionts.
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Affiliation(s)
- Theresa Backhaus
- 1 Institute of Botany, Heinrich Heine University, Duesseldorf, Germany
| | - Joachim Meeßen
- 1 Institute of Botany, Heinrich Heine University, Duesseldorf, Germany
| | - René Demets
- 2 European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Noordwijk, Netherlands
| | - Jean-Pierre de Vera
- 3 Research Group, Astrobiological Laboratories, Institute of Planetary Research, Management and Infrastructure, German Aerospace Center (DLR), Berlin, Germany
| | - Sieglinde Ott
- 1 Institute of Botany, Heinrich Heine University, Duesseldorf, Germany
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Wieners PC, Mudimu O, Bilger W. Survey of the occurrence of desiccation-induced quenching of basal fluorescence in 28 species of green microalgae. PLANTA 2018; 248:601-612. [PMID: 29846774 DOI: 10.1007/s00425-018-2925-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 05/22/2018] [Indexed: 06/08/2023]
Abstract
Desiccation-induced chlorophyll fluorescence quenching seems to be an indispensable part of desiccation resistance in the surveyed 28 green microalgal species. Lichens are desiccation tolerant meta-organisms. In the desiccated state photosynthesis is inhibited rendering the photobionts potentially sensitive to photoinhibition. As a photoprotective mechanism, strong non-radiative dissipation of absorbed light leading to quenching of chlorophyll fluorescence has been proposed. Desiccation-induced quenching affects not only variable fluorescence, but also the so-called basal fluorescence, F0. This phenomenon is well-known for intact lichens and some free living aero-terrestrial algae, but it was often absent in isolated lichen algae. Therefore, a thorough screening for the appearance of desiccation-induced quenching was undertaken with 13 different aero-terrestrial microalgal species and lichen photobionts. They were compared with 15 aquatic green microalgal species, among them also three marine species. We asked the following questions: Do isolated lichen algae show desiccation-induced quenching? Are aero-terrestrial algae different in this respect to aquatic algae and is the potential for desiccation-induced quenching coupled to desiccation tolerance? How variable is desiccation-induced quenching among species? Most of the aero-terrestrial algae, including all lichen photobionts, showed desiccation-induced quenching, although highly variable in extent, whereas most of the aquatic algae did not. All algae displaying quenching were also desiccation tolerant, whereas all algae unable to perform desiccation-induced quenching were desiccation intolerant. Desiccation-induced fluorescence quenching seems to be an indispensable part of desiccation resistance in the investigated species.
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Affiliation(s)
- Paul Christian Wieners
- Botanical Institute, Christian-Albrechts University of Kiel, Olshausenstraße 40, DE, 24098, Kiel, Germany.
| | - Opayi Mudimu
- Botanical Institute, Christian-Albrechts University of Kiel, Olshausenstraße 40, DE, 24098, Kiel, Germany
| | - Wolfgang Bilger
- Botanical Institute, Christian-Albrechts University of Kiel, Olshausenstraße 40, DE, 24098, Kiel, Germany
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Li H, Wei JC. Functional analysis of thioredoxin from the desert lichen-forming fungus, Endocarpon pusillum Hedwig, reveals its role in stress tolerance. Sci Rep 2016; 6:27184. [PMID: 27251605 PMCID: PMC4890037 DOI: 10.1038/srep27184] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 05/13/2016] [Indexed: 01/05/2023] Open
Abstract
Endocarpon pusillum is a lichen-forming fungus with an outstanding stress resistance property closely related to its antioxidant system. In this study, thioredoxin (Trx), one of the main components of antioxidant defense systems in E. pusillum (EpTrx), was characterized and analyzed both in transgenic yeasts and in vitro. Our analyses identified that the heterologous expression of EpTrx in the yeast Pichia pastoris significantly enhanced its resistance to osmotic and oxidative stresses. Assays in vitro showed EpTrx acted as a disulfide reductase as well as a molecular chaperone by assembling into various polymeric structures. Upon exposure to heat-shock stress, EpTrx exhibited weaker disulfide reductase activity but stronger chaperone activity, which coincided with the switching of the protein complexes from low molecular weight forms to high molecular weight complexes. Specifically, we found that Cys31 near but not at the active site was crucial in promoting the structural and functional transitions, most likely by accelerating the formation of intermolecular disulfide bond. Transgenic Saccharomyces cerevisiae harboring the native EpTrx exhibited stronger tolerance to oxidative, osmotic and high temperature stresses than the corresponding yeast strain containing the mutant EpTrx (C31S). Our results provide the first molecular evidence on how Trx influences stress response in lichen-forming fungi.
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Affiliation(s)
- Hui Li
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiang-Chun Wei
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Davila AF, Hawes I, Araya JG, Gelsinger DR, DiRuggiero J, Ascaso C, Osano A, Wierzchos J. In situ metabolism in halite endolithic microbial communities of the hyperarid Atacama Desert. Front Microbiol 2015; 6:1035. [PMID: 26500612 PMCID: PMC4594028 DOI: 10.3389/fmicb.2015.01035] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/11/2015] [Indexed: 01/01/2023] Open
Abstract
The Atacama Desert of northern Chile is one of the driest regions on Earth, with areas that exclude plants and where soils have extremely low microbial biomass. However, in the driest parts of the desert there are microorganisms that colonize the interior of halite nodules in fossil continental evaporites, where they are sustained by condensation of atmospheric water triggered by the salt substrate. Using a combination of in situ observations of variable chlorophyll fluorescence and controlled laboratory experiments, we show that this endolithic community is capable of carbon fixation both through oxygenic photosynthesis and potentially ammonia oxidation. We also present evidence that photosynthetic activity is finely tuned to moisture availability and solar insolation and can be sustained for days, and perhaps longer, after a wetting event. This is the first demonstration of in situ active metabolism in the hyperarid core of the Atacama Desert, and it provides the basis for proposing a self-contained, endolithic community that relies exclusively on non-rainfall sources of water. Our results contribute to an increasing body of evidence that even in hyperarid environments active metabolism, adaptation, and growth can occur in highly specialized microhabitats.
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Affiliation(s)
| | - Ian Hawes
- Gateway Antarctica, University of Canterbury , Christchurch, New Zealand
| | - Jonathan G Araya
- Laboratorio de Microorganismos Extremófilos, Instituto Antofagasta, Universidad de Antofagasta , Antofagasta, Chile
| | - Diego R Gelsinger
- Department of Biology, Johns Hopkins University , Baltimore, MD, USA
| | | | - Carmen Ascaso
- Grupo de Ecología y Geomicrobiología del Sustrato Lítico, Departamento de Biogeoquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales (MNCN), Consejo Superior de Investigaciones Científicas (CSIC) , Madrid, Spain
| | - Anne Osano
- Department of Natural Sciences, Bowie State University , Bowie, MD, USA
| | - Jacek Wierzchos
- Grupo de Ecología y Geomicrobiología del Sustrato Lítico, Departamento de Biogeoquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales (MNCN), Consejo Superior de Investigaciones Científicas (CSIC) , Madrid, Spain
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Holzinger A, Kaplan F, Blaas K, Zechmann B, Komsic-Buchmann K, Becker B. Transcriptomics of desiccation tolerance in the streptophyte green alga Klebsormidium reveal a land plant-like defense reaction. PLoS One 2014; 9:e110630. [PMID: 25340847 PMCID: PMC4207709 DOI: 10.1371/journal.pone.0110630] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 09/15/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Water loss has significant effects on physiological performance and survival rates of algae. However, despite the prominent presence of aeroterrestrial algae in terrestrial habitats, hardly anything is known about the molecular events that allow aeroterrestrial algae to survive harsh environmental conditions. We analyzed the transcriptome and physiology of a strain of the alpine aeroterrestrial alga Klebsormidium crenulatum under control and strong desiccation-stress conditions. PRINCIPAL FINDINGS For comparison we first established a reference transcriptome. The high-coverage reference transcriptome includes about 24,183 sequences (1.5 million reads, 636 million bases). The reference transcriptome encodes for all major pathways (energy, carbohydrates, lipids, amino acids, sugars), nearly all deduced pathways are complete or missing only a few transcripts. Upon strong desiccation, more than 7000 transcripts showed changes in their expression levels. Most of the highest up-regulated transcripts do not show similarity to known viridiplant proteins, suggesting the existence of some genus- or species-specific responses to desiccation. In addition, we observed the up-regulation of many transcripts involved in desiccation tolerance in plants (e.g. proteins similar to those that are abundant in late embryogenesis (LEA), or proteins involved in early response to desiccation ERD), and enzymes involved in the biosynthesis of the raffinose family of oligosaccharides (RFO) known to act as osmolytes). Major physiological shifts are the up-regulation of transcripts for photosynthesis, energy production, and reactive oxygen species (ROS) metabolism, which is supported by elevated cellular glutathione content as revealed by immunoelectron microscopy as well as an increase in total antiradical power. However, the effective quantum yield of Photosystem II and CO2 fixation decreased sharply under the applied desiccation stress. In contrast, transcripts for cell integrative functions such as cell division, DNA replication, cofactor biosynthesis, and amino acid biosynthesis were down-regulated. SIGNIFICANCE This is the first study investigating the desiccation transcriptome of a streptophyte green alga. Our results indicate that the cellular response is similar to embryophytes, suggesting that embryophytes inherited a basic cellular desiccation tolerance from their streptophyte predecessors.
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Affiliation(s)
- Andreas Holzinger
- University of Innsbruck, Functional Plant Biology, Innsbruck, Austria
| | - Franziska Kaplan
- University of Innsbruck, Functional Plant Biology, Innsbruck, Austria
| | - Kathrin Blaas
- University of Innsbruck, Functional Plant Biology, Innsbruck, Austria
| | - Bernd Zechmann
- Baylor University, Center for Microscopy and Imaging, Waco, Texas, United States of America
| | | | - Burkhard Becker
- University of Cologne, Botanical Institute, Biocenter, Cologne, Germany
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Nitschke U, Stengel DB. Iodine contributes to osmotic acclimatisation in the kelp Laminaria digitata (Phaeophyceae). PLANTA 2014; 239:521-30. [PMID: 24253307 DOI: 10.1007/s00425-013-1992-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/28/2013] [Indexed: 06/02/2023]
Abstract
Iodide (I⁻) retained by the brown macroalga Laminaria digitata at millimolar levels, possesses antioxidant activities, but the wider physiological significance of its accumulation remains poorly understood. In its natural habitat in the lower intertidal, L. digitata experiences salinity changes and osmotic homeostasis is achieved by regulating the organic osmolyte mannitol. However, I⁻ may also holds an osmotic function. Here, impacts of hypo- and hypersaline conditions on I⁻ release from, and accumulation by, L. digitata were assessed. Additionally, mannitol accumulation was determined at high salinities, and physiological responses to externally elevated iodine concentrations and salinities were characterised by chl a fluorometry. Net I⁻ release rates increased with decreasing salinity. I⁻ was accumulated at normal (35 S A) and high salinities (50 S A); this coincided with enhanced rETRmax and qP causing pronounced photoprotection capabilities via NPQ. At 50 S A elevated tissue iodine levels impeded the well-established response of mannitol accumulation and prevented photoinhibition. Contrarily, low tissue iodine levels limited photoprotection capabilities and resulted in photoinhibition at 50 S A, even though mannitol was accumulated. The results indicate a, so far, undescribed osmotic function of I⁻ in L. digitata and, thus, multifunctional principles of this halogen in kelps. The osmotic function of mannitol may have been substituted by that of I⁻ under hypersaline conditions, suggesting a complementary role of inorganic and organic solutes under salinity stress. This study also provides first evidence that iodine accumulation in L. digitata positively affects photo-physiology.
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Affiliation(s)
- Udo Nitschke
- Botany and Plant Science, School of Natural Sciences, and Ryan Institute for Environmental, Marine and Energy Research, National University of Ireland Galway, Galway, Ireland,
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Karsten U, Holzinger A. Green algae in alpine biological soil crust communities: acclimation strategies against ultraviolet radiation and dehydration. BIODIVERSITY AND CONSERVATION 2014; 23:1845-1858. [PMID: 24954980 PMCID: PMC4058318 DOI: 10.1007/s10531-014-0653-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/22/2014] [Accepted: 02/14/2014] [Indexed: 05/20/2023]
Abstract
Green algae are major components of biological soil crusts in alpine habitats. Together with cyanobacteria, fungi and lichens, green algae form a pioneer community important for the organisms that will succeed them. In their high altitudinal habitat these algae are exposed to harsh and strongly fluctuating environmental conditions, mainly intense irradiation, including ultraviolet radiation, and lack of water leading to desiccation. Therefore, green algae surviving in these environments must have evolved with either avoidance or protective strategies, as well as repair mechanisms for damage. In this review we have highlighted these mechanisms, which include photoprotection, photochemical quenching, and high osmotic values to avoid water loss, and in some groups flexibility of secondary cell walls to maintain turgor pressure even in water-limited situations. These highly specialized green algae will serve as good model organisms to study desiccation tolerance or photoprotective mechanisms, due to their natural capacity to withstand unfavorable conditions. We point out the urgent need for modern phylogenetic approaches in characterizing these organisms, and molecular methods for analyzing the metabolic changes involved in their adaptive strategies.
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Affiliation(s)
- Ulf Karsten
- Institute of Biological Sciences, Applied Ecology and Phycology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany
| | - Andreas Holzinger
- Functional Plant Biology, Institute of Botany, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria
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Holzinger A, Karsten U. Desiccation stress and tolerance in green algae: consequences for ultrastructure, physiological and molecular mechanisms. FRONTIERS IN PLANT SCIENCE 2013; 4:327. [PMID: 23986769 PMCID: PMC3749462 DOI: 10.3389/fpls.2013.00327] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 08/02/2013] [Indexed: 05/18/2023]
Abstract
Although most green algae typically occur in aquatic ecosystems, many species also live partly or permanently under aeroterrestrial conditions, where the cells are exposed to the atmosphere and hence regularly experience dehydration. The ability of algal cells to survive in an air-dried state is termed desiccation tolerance. The mechanisms involved in desiccation tolerance of green algae are still poorly understood, and hence the aim of this review is to summarize recent findings on the effects of desiccation and osmotic water loss. Starting from structural changes, physiological, and biochemical consequences of desiccation will be addressed in different green-algal lineages. The available data clearly indicate a range of strategies, which are rather different in streptophycean and non-streptophycean green algae. While members of the Trebouxiophyceae exhibit effective water loss-prevention mechanisms based on the biosynthesis and accumulation of particular organic osmolytes such as polyols, these compounds are so far not reported in representatives of the Streptophyta. In members of the Streptophyta such as Klebsormidium, the most striking observation is the appearance of cross-walls in desiccated samples, which are strongly undulating, suggesting a high degree of mechanical flexibility. This aids in maintaining structural integrity in the dried state and allows the cell to maintain turgor pressure for a prolonged period of time during the dehydration process. Physiological strategies in aeroterrestrial green algae generally include a rapid reduction of photosynthesis during desiccation, but also a rather quick recovery after rewetting, whereas aquatic species are sensitive to drying. The underlying mechanisms such as the affected molecular components of the photosynthetic machinery are poorly understood in green algae. Therefore, modern approaches based on transcriptomics, proteomics, and/or metabolomics are urgently needed to better understand the molecular mechanisms involved in desiccation-stress physiology of these organisms. The very limited existing information is described in the present review.
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Affiliation(s)
- Andreas Holzinger
- Functional Plant Biology, Institute of Botany, University of InnsbruckInnsbruck, Austria
| | - Ulf Karsten
- Applied Ecology and Phycology, Institute of Biological Sciences, University of RostockRostock, Germany
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Holzinger A, Karsten U. Desiccation stress and tolerance in green algae: consequences for ultrastructure, physiological and molecular mechanisms. FRONTIERS IN PLANT SCIENCE 2013. [PMID: 23986769 DOI: 10.3389/fpls.2013.0327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Although most green algae typically occur in aquatic ecosystems, many species also live partly or permanently under aeroterrestrial conditions, where the cells are exposed to the atmosphere and hence regularly experience dehydration. The ability of algal cells to survive in an air-dried state is termed desiccation tolerance. The mechanisms involved in desiccation tolerance of green algae are still poorly understood, and hence the aim of this review is to summarize recent findings on the effects of desiccation and osmotic water loss. Starting from structural changes, physiological, and biochemical consequences of desiccation will be addressed in different green-algal lineages. The available data clearly indicate a range of strategies, which are rather different in streptophycean and non-streptophycean green algae. While members of the Trebouxiophyceae exhibit effective water loss-prevention mechanisms based on the biosynthesis and accumulation of particular organic osmolytes such as polyols, these compounds are so far not reported in representatives of the Streptophyta. In members of the Streptophyta such as Klebsormidium, the most striking observation is the appearance of cross-walls in desiccated samples, which are strongly undulating, suggesting a high degree of mechanical flexibility. This aids in maintaining structural integrity in the dried state and allows the cell to maintain turgor pressure for a prolonged period of time during the dehydration process. Physiological strategies in aeroterrestrial green algae generally include a rapid reduction of photosynthesis during desiccation, but also a rather quick recovery after rewetting, whereas aquatic species are sensitive to drying. The underlying mechanisms such as the affected molecular components of the photosynthetic machinery are poorly understood in green algae. Therefore, modern approaches based on transcriptomics, proteomics, and/or metabolomics are urgently needed to better understand the molecular mechanisms involved in desiccation-stress physiology of these organisms. The very limited existing information is described in the present review.
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Affiliation(s)
- Andreas Holzinger
- Functional Plant Biology, Institute of Botany, University of Innsbruck Innsbruck, Austria
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