Seedling Growth-2 (Seedling Growth-2) - 10.21.14
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Plants play a central role in the future planning of long-term manned space missions, as they serve as a source of food and generate breathable air for crew members. Seedling Growth-2 is the second part of a series of investigations that uses the plant Arabidopsis thaliana to help determine the effects of microgravity and light on plant growth, development, and cell proliferation/cell cycle. The plants are grown in different wavelengths of light (red and blue), and both the plant growth and the expression of selected genes are compared to plants grown on Earth (as well as to the 1-g control on the International Space Station) under the same lighting conditions.
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OpNom Seedling Growth-2
NASA Ames Research Center, Moffett Field, CA, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
September 2014 - March 2015
Previous ISS Missions
TROPI-2; TROPI2; GENARA-A; Seedling Growth-1
The goal of Seedling Growth-2 is to determine the combined effects of gravity and light on cellular signaling mechanisms of phototropism and to know the cellular response to light stimulation in microgravity conditions, regarding cell growth and proliferation, specifically cell cycle regulation. Improved knowledge of these basic mechanistic processes is vital to use plants in bioregenerative life support system, in exploration initiatives in future travel beyond low-Earth orbit.
First, the effects and influence of gravity on light responses on Arabidopsis thalania are determined to better understand cellular signaling mechanisms of phototropism. Second, the relationship between light and gravity by measuring the shoots in fractional gravity is to be investigated. Third, the investigation seeks to resolve the cellular response to light stimulation under environmental conditions of microgravity or fractional gravity in space. Fourth, the research focuses on root cell growth and proliferation, two basic and essential cell processes which are fundamental for the plant developmental program. Genes participating in the regulation of ribosome biogenesis and cell cycle will be analyzed as markers of these cellular activities.
This project is an international collaborative effort among scientists in Spain, France, and the USA. From a scientific perspective, the project intends to establish a relationship between two biological processes already investigated in microgravity, namely light stimulation and cell proliferation, including the role played by the key plant hormone auxin.
This experiment builds on previous spaceflight experiments for both Principal Investigators (Dr. John Z. Kiss and Dr. F. Javier Medina) using the model plant Arabidopsis thaliana to study the combined effects of light and gravity on plant growth, development and proliferation.
The experiment is a collaboration between a NASA PI (Kiss) and an ESA PI (Medina) and is co-sponsored by NASA and ESA.
In previous experiments by the PIs in the EMCS on the ISS, data were obtained on the phytochrome photoreceptors responsible for the plant growth in response of light, or phototropism, of seedlings grown in microgravity. Growth, development, and phototropic curvature of plants in response to varying qualities of light were analyzed, as well as global gene expression changes using DNA microarrays.
In the ROOT experiment (Medina, ISS), and in complementary experiments approached until now in ground-based facilities, results indicated that cell growth and proliferation in root meristems were altered by changing the effective gravity, including the expression of relevant cell cycle genes and the features of essential regulators of ribosome biogenesis. Furthermore, the distribution of auxin was altered, resulting in modifications of the pattern of primary and secondary root growth.
Since previous research has already shown the perception phase of phototropism, this experiment focuses on the signal transduction phase and on the crosstalk between the red and blue light signaling pathways, by means of the use of different mutants in the transduction pathways. The contribution of light stimuli to the regulation of cell growth and proliferation is evaluated by using red-light treatments to auxin mutants and to ribosome biogenesis mutants. On these materials, postflight analyses including real-time Polymerase Chain Reaction (RT-PCR) and proteomic methods are to be performed.
Since down mass is limited in the spaceflight opportunities, a part of these experiments are to be accomplished with telescience and, during experimental runs, images of seedlings are downlinked to Earth.
Significant to the success of this proposal is that the PI teams are already experienced with the EMCS. The US group was the first group to successfully use this research facility on the ISS in a project termed as outlined in recent publications (Kiss et al. 2011; Millar et al. 2010). The European groups have used the EMCS in the GENARA-A experiment (Mazars et al., 2014). In addition, the PIs have done extensive ground-based testing at NASA facilities and have performed tests in Europe on the engineering and flight models.
In terms of long-term research goals, the flowering plant Arabidopsis is an excellent model for spaceflight experiments because of its small size and simple growth requirements. A number of US and international agencies have supported Arabidopsis research efforts, including the establishment major genome programs. Indeed, Arabidopsis has already proven to be a valuable experimental model during several spaceflight experiments by our group and others. Again, since the EMCS has a variable speed centrifuge, this project is also relevant to the emphasis to understand how plant growth and development occurs at fractional g-levels, such as those found on the Moon and Mars.
The major focus of this project is to determine how gravity and light responses influence each other in plants, and to better understand the cellular signaling mechanisms involved in how plants react to light. Additionally, using the European Modular Cultivation System, it is possible to study plant growth and development at fractional gravity levels as would be seen on the Moon or Mars. Improving the knowledge base of these basic processes is important as ways are developed to use plants in future bioregenerative life support systems for future manned missions.
Light and gravity sensing are key parameters in plant growth and development. Further understanding of how plants are affected by these factors helps in the development of strategies to optimize light sensing in plants, and modifying plant species by using biotechnological approaches to improve crop plants. Improvements in agricultural biotechnology lead to increased crop production, lessened environmental impact, and a greater sustainability of agricultural production to benefit human agriculture on Earth.
ECs/EUE/Seed Cassettes are delivered to ISS via cargo vehicle. For launch, ECs should be oriented such that launch loads are perpendicular to the base plate. At times to be determined, experiment images are automatically downlinked to Earth. A functional EMCS is required to conduct the experiment runs. For return to Earth, Seed Cassettes should be frozen, and ECs should be returned at ambient temperature.
Crew members install ECs into EMCS Facility for run #1. The experiment is initiated by the crew, and by ground command from N-USOC, Norway. At conclusion of run #1, the crew removes ECs from EMCS. The crew then removes Seed Cassettes and places the Seed Cassettes in EMCS Cold Storage Bags, and freezes them in MELFI. The crew installs ECs in EMCS and repeats the experiment as run #2 with new ECs. At the end of run #2, the crew removes the ECs from the EMCS, removes the Seed Cassettes, and places the Seed Cassettes in EMCS Cold Storage Bags, and freezes them in MELFI. The crew installs 8 ECs in the EMCS and conducts the experiment as run #3. At conclusion of run #3, the crew removes the 8 ECs from the EMCS. The crew removes the Seed Cassettes and places the Seed Cassettes in EMCS Cold Storage Bags, and freezes in MELFI. The crew places the ECs in ambient stowage until return to Earth. For return to Earth, all frozen Seed Cassettes are placed in GLACIER.
Ground Based Results Publications
Matia I, Gonzalez-Camacho F, Herranz R, Herranz R, Kiss JZ, Kiss JZ, Kiss JZ, Kiss JZ, Gasset G, van Loon JJ, van Loon JJ, Marco R, Medina F, Medina F. Plant Cell Proliferation and Growth Are Altered by Microgravity Conditions in Spaceflight. Journal of Plant Physiology. 2010; 167(3): 184-193.
Kiss JZ, Kiss JZ, Kiss JZ, Kiss JZ, Kumar P, Millar KD, Millar KD, Edelmann RE, Edelmann RE, Correll MJ. Operations of a spaceflight experiment to investigate plant tropisms. Advances in Space Research. 2009; 44(8): 879-886. DOI: 10.1016/l.asr.2009.06.007.
Millar KD, Millar KD, Kumar P, Correll MJ, Mullen JL, Hangarter RP, Edelmann RE, Edelmann RE, Kiss JZ, Kiss JZ, Kiss JZ, Kiss JZ. A novel phototropic response to red light is revealed in microgravity. New Phytologist. 2010; 186(3): 648-656. DOI: 10.1111/j.1469-8137.2010.03211.x.
Kiss JZ, Kiss JZ, Kiss JZ, Kiss JZ, Millar KD, Millar KD, Edelmann RE, Edelmann RE. Phototropism of Arabidopsis thaliana in microgravity and fractional gravity on the International Space Station. Planta. 2012; 236(2): 635-645. DOI: 10.1007/s00425-012-1633-y. PMID: 22481136.
Kiss JZ, Kiss JZ, Kiss JZ, Kiss JZ, Millar KD, Millar KD, Kumar P, Edelmann RE, Edelmann RE, Correll MJ. Improvements in the re-flight of spaceflight experiments on plant tropisms. Advances in Space Research. 2011; 47(3): 545-552. DOI: 10.1016/j.asr.2010.09.024.
Department of Botany/John Kiss
Space Biosciences Division
Tropi cassette. Image courtesy of John Kiss.
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Tropi still image. Image courtesy of John Kiss.
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