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De Micco V, Amitrano C, Mastroleo F, Aronne G, Battistelli A, Carnero-Diaz E, De Pascale S, Detrell G, Dussap CG, Ganigué R, Jakobsen ØM, Poulet L, Van Houdt R, Verseux C, Vlaeminck SE, Willaert R, Leys N. Plant and microbial science and technology as cornerstones to Bioregenerative Life Support Systems in space. NPJ Microgravity 2023; 9:69. [PMID: 37620398 PMCID: PMC10449850 DOI: 10.1038/s41526-023-00317-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 08/02/2023] [Indexed: 08/26/2023] Open
Abstract
Long-term human space exploration missions require environmental control and closed Life Support Systems (LSS) capable of producing and recycling resources, thus fulfilling all the essential metabolic needs for human survival in harsh space environments, both during travel and on orbital/planetary stations. This will become increasingly necessary as missions reach farther away from Earth, thereby limiting the technical and economic feasibility of resupplying resources from Earth. Further incorporation of biological elements into state-of-the-art (mostly abiotic) LSS, leading to bioregenerative LSS (BLSS), is needed for additional resource recovery, food production, and waste treatment solutions, and to enable more self-sustainable missions to the Moon and Mars. There is a whole suite of functions crucial to sustain human presence in Low Earth Orbit (LEO) and successful settlement on Moon or Mars such as environmental control, air regeneration, waste management, water supply, food production, cabin/habitat pressurization, radiation protection, energy supply, and means for transportation, communication, and recreation. In this paper, we focus on air, water and food production, and waste management, and address some aspects of radiation protection and recreation. We briefly discuss existing knowledge, highlight open gaps, and propose possible future experiments in the short-, medium-, and long-term to achieve the targets of crewed space exploration also leading to possible benefits on Earth.
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Affiliation(s)
- Veronica De Micco
- Department of Agricultural Sciences, University of Naples Federico II, via Università 100, 80055, Portici (NA), Italy.
| | - Chiara Amitrano
- Department of Agricultural Sciences, University of Naples Federico II, via Università 100, 80055, Portici (NA), Italy
| | - Felice Mastroleo
- Microbiology Unit, Nuclear Medical Applications, Belgian Nuclear Research Centre (SCK CEN), 2400, Mol, Belgium
| | - Giovanna Aronne
- Department of Agricultural Sciences, University of Naples Federico II, via Università 100, 80055, Portici (NA), Italy
| | - Alberto Battistelli
- Istituto di Ricerca sugli Ecosistemi Terrestri Consiglio Nazionale delle Ricerche Viale Marconi 2, 05010, Porano (TR), Italy
| | - Eugenie Carnero-Diaz
- Institute of Systematic, Evolution, Biodiversity, Sorbonne University, National Museum of Natural History, CNRS, EPHE, UA, 45, rue Buffon CP50, 75005, Paris, France
| | - Stefania De Pascale
- Department of Agricultural Sciences, University of Naples Federico II, via Università 100, 80055, Portici (NA), Italy
| | - Gisela Detrell
- Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, 70569, Stuttgart, Germany
| | - Claude-Gilles Dussap
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, Institut Pascal, F-63000, Clermont-Ferrand, France
| | - Ramon Ganigué
- Center for Microbial Ecology and Technology, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Øyvind Mejdell Jakobsen
- Centre for Interdisciplinary Research in Space (CIRiS), NTNU Social Research, Trondheim, Norway
| | - Lucie Poulet
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, Institut Pascal, F-63000, Clermont-Ferrand, France
| | - Rob Van Houdt
- Microbiology Unit, Nuclear Medical Applications, Belgian Nuclear Research Centre (SCK CEN), 2400, Mol, Belgium
| | - Cyprien Verseux
- Center of Applied Space Technology and Microgravity (ZARM), University of Bremen, 28359, Bremen, Germany
| | - Siegfried E Vlaeminck
- Research Group of Sustainable Energy, Air and Water Technology, University of Antwerp, 2020, Antwerpen, Belgium
| | - Ronnie Willaert
- Research Groups NAMI and NANO, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium
| | - Natalie Leys
- Microbiology Unit, Nuclear Medical Applications, Belgian Nuclear Research Centre (SCK CEN), 2400, Mol, Belgium
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Iovane M, Aronne G. High temperatures during microsporogenesis fatally shorten pollen lifespan. PLANT REPRODUCTION 2022; 35:9-17. [PMID: 34232397 PMCID: PMC8854315 DOI: 10.1007/s00497-021-00425-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 06/28/2021] [Indexed: 06/13/2023]
Abstract
Many crop species are cultivated to produce seeds and/or fruits and therefore need reproductive success to occur. Previous studies proved that high temperature on mature pollen at anther dehiscence reduce viability and germinability therefore decreasing crop productivity. We hypothesized that high temperature might affect pollen functionality even if the heat treatment is exerted only during the microsporogenesis. Experimental data on Solanum lycopersicum 'Micro-Tom' confirmed our hypothesis. Microsporogenesis successfully occurred at both high (30 °C) and optimal (22 °C) temperature. After the anthesis, viability and germinability of the pollen developed at optimal temperature gradually decreased and the reduction was slightly higher when pollen was incubated at 30 °C. Conversely, temperature effect was eagerly enhanced in pollen developed at high temperature. In this case, a drastic reduction of viability and a drop-off to zero of germinability occurred not only when pollen was incubated at 30 °C but also at 22 °C. Further ontogenetic analyses disclosed that high temperature significantly speeded-up the microsporogenesis and the early microgametogenesis (from vacuolated stage to bi-cellular pollen); therefore, gametophytes result already senescent at flower anthesis. Our work contributes to unravel the effects of heat stress on pollen revealing that high temperature conditions during microsporogenesis prime a fatal shortening of the male gametophyte lifespan.
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Affiliation(s)
- Maurizio Iovane
- Department of Agricultural Sciences, University of Naples Federico II, Naples, Italy.
| | - Giovanna Aronne
- Department of Agricultural Sciences, University of Naples Federico II, Naples, Italy
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De Pascale S, Arena C, Aronne G, De Micco V, Pannico A, Paradiso R, Rouphael Y. Biology and crop production in Space environments: Challenges and opportunities. LIFE SCIENCES IN SPACE RESEARCH 2021; 29:30-37. [PMID: 33888285 DOI: 10.1016/j.lssr.2021.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/12/2021] [Accepted: 02/28/2021] [Indexed: 05/09/2023]
Abstract
Long-term manned space-exploration missions and the permanence of human colonies on orbital stations or planetary habitats will require the regeneration of resources onboard or in-situ. Bioregenerative Life Support Systems (BLSSs) are artificial environments where different compartments, involving both living organisms and physical-chemical processes, are integrated to achieve a safe, self-regulating, and chemically balanced Earth-like environment to support human life. Higher plants are key elements of such systems and Space greenhouses represent the producers' compartment. Growing plants in Space requires the knowledge of their growth responses not only to all environmental factors acting on Earth, but also to specific Space constraints such as altered gravity, ionizing radiations and confined volume. Moreover, cultivation techniques need to be adjusted considering such limitations. The type and intensity of environmental factors to be taken into account depend on the mission scenarios. Here, we summarize constraints and opportunities of cultivating higher plants in Space to regenerate resources and produce fresh food onboard. Both biological and agro-technological issues are considered briefly going through experiments both ground-based on Earth and in Space.
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Affiliation(s)
- S De Pascale
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy
| | - C Arena
- Department of Biology, University of Naples Federico II, Via Cinthia, 80126 Naples, Italy
| | - G Aronne
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy
| | - V De Micco
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy.
| | - A Pannico
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy
| | - R Paradiso
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy
| | - Y Rouphael
- Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Portici, Naples, Italy
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Faraoni P, Sereni E, Gnerucci A, Cialdai F, Monici M, Ranaldi F. Glyoxylate cycle activity in Pinus pinea seeds during germination in altered gravity conditions. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 139:389-394. [PMID: 30959447 DOI: 10.1016/j.plaphy.2019.03.042] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 03/28/2019] [Accepted: 03/28/2019] [Indexed: 06/09/2023]
Abstract
This work inserts in the research field regarding the effects of altered gravity conditions on biological plant processes. Pinus pinea seeds germination was studied in simulated microgravity (2x10-3g) and hypergravity (20g) conditions. The effects of simulated gravity were evaluated monitoring the levels of the key enzymes, involved in the main metabolic pathway during germination process of lipid-rich seeds (oilseeds): isocitrate lyase and malate synthase for glyoxylate cycle, 3-hydroxyacyl-CoA dehydrogenase for beta-oxidation, isocitrate dehydrogenase for Krebs cycle, pyruvate kinase for glycolysis and glucose 6 phosphate dehydrogenase for pentose phosphate shunt. The simulated micro and hypergravity conditions were obtained by a Random Position Machine and a Hyperfuge, respectively. Results show that the levels of some tested enzymes, at different lag times of the germination process, have the same trend of controls (g = 1), but with significant differences from quantitative point of view. They are higher in microgravity conditions and lower in hypergravity ones, suggesting that, from a biochemical point of view, the germination process results accelerated in microgravity conditions and delayed in hypergravity ones. These biochemical results show a good correlation with morphological ones, obtained with the measurement of the length of the seeds sprouting radicle. These results give promising indications regarding the possibility to grow plant with lipid-rich seeds in spatial environment, to obtain food sources for astronauts during long term space missions and to reconstitute new atmosphere.
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Affiliation(s)
- Paola Faraoni
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini 6, I-50139, Florence, Italy.
| | - Elettra Sereni
- ASAcampus Joint Laboratory, ASA Research Division & Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale G. Pieraccini 6, I-50139, Florence, Italy
| | - Alessio Gnerucci
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini 6, I-50139, Florence, Italy
| | - Francesca Cialdai
- ASAcampus Joint Laboratory, ASA Research Division & Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale G. Pieraccini 6, I-50139, Florence, Italy
| | - Monica Monici
- ASAcampus Joint Laboratory, ASA Research Division & Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale G. Pieraccini 6, I-50139, Florence, Italy
| | - Francesco Ranaldi
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini 6, I-50139, Florence, Italy
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Chebli Y, Geitmann A. Live cell and immuno-labeling techniques to study gravitational effects on single plant cells. Methods Mol Biol 2015; 1309:209-226. [PMID: 25981778 DOI: 10.1007/978-1-4939-2697-8_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The constant force of gravity plays a primordial role in the ontogeny of all living organisms. Plants, for example, develop their roots and shoots in accordance with the direction of the gravitational vector. Any change in the magnitude and/or the direction of gravity has an important impact on the development of tissues and cells. In order to understand how the gravitational force affects plant cell growth and differentiation, we established two complementary experimental procedures with which the effect of hyper-gravity on single plant cell development can be assessed. The single model cell system we used is the pollen tube or male gametophyte which, because of its rapid growth behavior, is known for its instant response to external stresses. The physiological response of the pollen tube can be assessed in a quantitative manner based on changes in the composition and spatial distribution of its cell wall components and in the precisely defined pattern of its very dynamic cytoplasmic streaming. Here, we provide a detailed description of the steps required for the immuno-localization of various cell wall components using microwave-assisted techniques and we explain how live imaging of the intracellular traffic can be achieved under hyper-gravity conditions.
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Affiliation(s)
- Youssef Chebli
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, 4101 Sherbrooke East, Montreal, QC, Canada, H1X 2B2
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Leaf anatomy and photochemical behaviour of Solanum lycopersicum L. plants from seeds irradiated with low-LET ionising radiation. ScientificWorldJournal 2014; 2014:428141. [PMID: 24883400 PMCID: PMC4030580 DOI: 10.1155/2014/428141] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 03/17/2014] [Indexed: 11/18/2022] Open
Abstract
Plants can be exposed to ionising radiation not only in Space but also on Earth, due to specific technological applications or after nuclear disasters. The response of plants to ionising radiation depends on radiation quality/quantity and/or plant characteristics. In this paper, we analyse some growth traits, leaf anatomy, and ecophysiological features of plants of Solanum lycopersicum L. "Microtom" grown from seeds irradiated with increasing doses of X-rays (0.3, 10, 20, 50, and 100 Gy). Both juvenile and compound leaves from plants developed from irradiated and control seeds were analysed through light and epifluorescence microscopy. Digital image analysis allowed quantifying anatomical parameters to detect the occurrence of signs of structural damage. Fluorescence parameters and total photosynthetic pigment content were analysed to evaluate the functioning of the photosynthetic machinery. Radiation did not affect percentage and rate of seed germination. Plants from irradiated seeds accomplished the crop cycle and showed a more compact habitus. Dose-depended tendencies of variations occurred in phenolic content, while other leaf anatomical parameters did not show distinct trends after irradiation. The sporadic perturbations of leaf structure, observed during the vegetative phase, after high levels of radiation were not so severe as to induce any significant alterations in photosynthetic efficiency.
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De Micco V, De Pascale S, Paradiso R, Aronne G. Microgravity effects on different stages of higher plant life cycle and completion of the seed-to-seed cycle. PLANT BIOLOGY (STUTTGART, GERMANY) 2014; 16 Suppl 1:31-8. [PMID: 24015754 DOI: 10.1111/plb.12098] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 07/18/2013] [Indexed: 05/25/2023]
Abstract
Human inhabitation of Space requires the efficient realisation of crop cultivation in bioregenerative life-support systems (BLSS). It is well known that plants can grow under Space conditions; however, perturbations of many biological phenomena have been highlighted due to the effect of altered gravity and its possible interactions with other factors. The mechanisms priming plant responses to Space factors, as well as the consequences of such alterations on crop productivity, have not been completely elucidated. These perturbations can occur at different stages of plant life and are potentially responsible for failure of the completion of the seed-to-seed cycle. After brief consideration of the main constraints found in the most recent experiments aiming to produce seeds in Space, we focus on two developmental phases in which the plant life cycle can be interrupted more easily than in others also on Earth. The first regards seedling development and establishment; we discuss reasons for slow development at the seedling stage that often occurs under microgravity conditions and can reduce successful establishment. The second stage comprises gametogenesis and pollination; we focus on male gamete formation, also identifying potential constraints to subsequent fertilisation. We finally highlight how similar alterations at cytological level can not only be common to different processes occurring at different life stages, but can be primed by different stress factors; such alterations can be interpreted within the model of 'stress-induced morphogenic response' (SIMR). We conclude by suggesting that a systematic analysis of all growth and reproductive phases during the plant life cycle is needed to optimise resource use in plant-based BLSS.
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Affiliation(s)
- V De Micco
- Department of Agriculture, University of Naples Federico II, Portici, Naples, Italy
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Tamaoki D, Karahara I, Nishiuchi T, Wakasugi T, Yamada K, Kamisaka S. Effects of hypergravity stimulus on global gene expression during reproductive growth in Arabidopsis. PLANT BIOLOGY (STUTTGART, GERMANY) 2014; 16 Suppl 1:179-186. [PMID: 24373015 DOI: 10.1111/plb.12124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 09/27/2013] [Indexed: 06/03/2023]
Abstract
The life cycle of higher plants consists of successive vegetative and reproductive growth phases. Understanding effects of altered gravity conditions on the reproductive growth is essential, not only to elucidate how higher plants evolved under gravitational condition on Earth but also to approach toward realization of agriculture in space. In the present study, a comprehensive analysis of global gene expression of floral buds under hypergravity was carried out to understand effects of altered gravity on reproductive growth at molecular level. Arabidopsis plants grown for 20-26 days were exposed to hypergravity of 300 g for 24 h. Total RNA was extracted from flower buds and microarray (44 K) analysis performed. As a result, hypergravity up-regulated expression of a gene related to β-1,3-glucanase involved in pectin modification, and down-regulated β-galactosidase and amino acid transport, which supports a previous study reporting inhibition of pollen development and germination under hypergravity. With regard to genes related to seed storage accumulation, hypergravity up-regulated expression of genes of aspartate aminotransferase, and down-regulated those related to cell wall invertase and sugar transporter, supporting a previous study reporting promotion of protein body development and inhibition of starch accumulation under hypergravity, respectively. In addition, hypergravity up-regulated expression of G6PDH and GPGDH, which supports a previous study reporting promotion of lipid deposition under hypergravity. In addition, analysis of the metabolic pathway revealed that hypergravity substantially changed expression of genes involved in the biosynthesis of phytohormones such as abscisic acid and auxin.
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Affiliation(s)
- D Tamaoki
- Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
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Chebli Y, Pujol L, Shojaeifard A, Brouwer I, van Loon JJWA, Geitmann A. Cell wall assembly and intracellular trafficking in plant cells are directly affected by changes in the magnitude of gravitational acceleration. PLoS One 2013; 8:e58246. [PMID: 23516452 PMCID: PMC3596410 DOI: 10.1371/journal.pone.0058246] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 02/05/2013] [Indexed: 01/17/2023] Open
Abstract
Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of gravity on the metabolism and cellular functioning of non-specialized plant cells, we investigated a rapidly growing plant cell devoid of known statoliths and without gravitropic behavior, the pollen tube. The effects of hyper-gravity and omnidirectional exposure to gravity on intracellular trafficking and on cell wall assembly were assessed in Camellia pollen tubes, a model system with highly reproducible growth behavior in vitro. Using an epi-fluorescence microscope mounted on the Large Diameter Centrifuge at the European Space Agency, we were able to demonstrate that vesicular trafficking is reduced under hyper-gravity conditions. Immuno-cytochemistry confirmed that both in hyper and omnidirectional gravity conditions, the characteristic spatial profiles of cellulose and callose distribution in the pollen tube wall were altered, in accordance with a dose-dependent effect on pollen tube diameter. Our findings suggest that in response to gravity induced stress, the pollen tube responds by modifying cell wall assembly to compensate for the altered mechanical load. The effect was reversible within few minutes demonstrating that the pollen tube is able to quickly adapt to changing stress conditions.
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Affiliation(s)
- Youssef Chebli
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Lauranne Pujol
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Anahid Shojaeifard
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | | | - Jack J. W. A. van Loon
- Department of Craniofacial Surgery & Oral Cell Biology, Academisch Centrum Tandheelkunde Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Research Institute MOVE, Amsterdam, The Netherlands
- Life and Physical Sciences Instrumentation and Life Support Section (TEC-MMG), European Space Agency (ESA), Noordwijk, The Netherlands
| | - Anja Geitmann
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada
- * E-mail:
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Chebli Y, Geitmann A. Gravity research on plants: use of single-cell experimental models. FRONTIERS IN PLANT SCIENCE 2011; 2:56. [PMID: 22639598 PMCID: PMC3355640 DOI: 10.3389/fpls.2011.00056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Accepted: 09/05/2011] [Indexed: 05/10/2023]
Abstract
Future space missions and implementation of permanent bases on Moon and Mars will greatly depend on the availability of ambient air and sustainable food supply. Therefore, understanding the effects of altered gravity conditions on plant metabolism and growth is vital for space missions and extra-terrestrial human existence. In this mini-review we summarize how plant cells are thought to perceive changes in magnitude and orientation of the gravity vector. The particular advantages of several single-celled model systems for gravity research are explored and an overview over recent advancements and potential use of these systems is provided.
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Affiliation(s)
- Youssef Chebli
- Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de MontréalMontréal, QC, Canada
| | - Anja Geitmann
- Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de MontréalMontréal, QC, Canada
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Musgrave ME, Kuang A, Allen J, van Loon JJWA. Hypergravity prevents seed production in Arabidopsis by disrupting pollen tube growth. PLANTA 2009; 230:863-70. [PMID: 19649651 DOI: 10.1007/s00425-009-0992-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 07/17/2009] [Indexed: 05/25/2023]
Abstract
How tightly land plants are adapted to the gravitational force (g) prevailing on Earth has been of interest because unlike many other environmental factors, g presents as a constant force. Ontogeny of mature angiosperms begins with an embryo that is formed after tip growth by a pollen tube delivers the sperm nucleus to the egg. Because of the importance to plant fitness, we have investigated how gravity affects these early stages of reproductive development. Arabidopsis thaliana (L.) Heynh. plants were grown for 13 days prior to being transferred to growth chambers attached to a large diameter rotor, where they were continuously exposed to 2-g or 4-g for the subsequent 11 days. Plants began flowering 1 day after start of the treatments, producing hundreds of flowers for analysis of reproductive development. At 4-g, Arabidopsis flowers self-pollinated normally but did not produce seeds, thus derailing the entire life cycle. Pollen viability and stigma esterase activity were not compromised by hypergravity; however, the growth of pollen tubes into the stigmas was curtailed at 4-g. In vitro pollen germination assays showed that 4-g average tube length was less than half that for 1-g controls. Closely related Brassica rapa L., which produces seeds at 4-g, required forces in excess of 6-g to slow in vitro tube growth to half that at 1-g. The results explain why seed production is absent in Arabidopsis at 4-g and point to species differences with regard to the g-sensitivity of pollen tube growth.
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Affiliation(s)
- Mary E Musgrave
- Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT 06269, USA.
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