Arabidopsis Thaliana in Space: Perception of Gravity, Signal Transduction and Graviresponse in Higher Plants (AT-Space) - 05.13.15
The objective of Arabidopsis Thaliana in Space: Perception of Gravity, Signal Transduction and Graviresponse in Higher Plants (AT-Space) is to identify plant gravity perception and signal transduction pathways on a molecular level. This comprehensive research should reveal the crucial factors controlling the gravity signal transduction cascade. Science Results for Everyone
The AT-Space experiment studies the gravity sensitivity of the model cress plant Arabidopsis thaliana and how a change in gravity affects growth and development. Genetic analysis revealed that specific pathways worked together to handle the tress caused by microgravity. Knowing which genes are activated, or in some way regulated, by gravity has practical applications for regulating plant growth in space. Scientific tools and methods used in this experiment are of significant interest to the field of gene analysis and provide new information on gravity-regulated gene expression. Experiment Details
Alexander Dovzhenko, Ph.D., Albert-Ludwigs-Universitat Freiburg, Freiburg, Germany
Dorothee Aubry, M.Sc., Albert-Ludwigs-Universitat Freiburg, Freiburg, Germany
Franck Ditengou, Ph.D., Albert-Ludwigs-Universitat Freiburg, Freiburg, Germany
Klaus Palme, Ph.D., Albert-Ludwigs-Universitat Freiburg, Freiburg, Germany
Kayser Italia Srl., Livorno, Italy
Sponsoring Space Agency
European Space Agency (ESA)
ISS Expedition Duration
October 2007 - April 2008
Previous ISS Missions
- Arabidopsis Thaliana in Space: Perception of Gravity, Signal Transduction and Graviresponse in Higher Plants (AT-Space) will elucidate the mechanisms of plant root gravity perception and signal transduction and identify gravity related genes and localize gravity related proteins using a gene expression by microarray postflight.
- This investigation will answer the following questions:
- Does gravity drive the expression of particular classes of genes?
- Does gravity influence the expression of the same genes in different organs, such as roots and shoots?
- Are the same genes regulated by gravity on the ground and in space-grown plants?
The aim of the proposal is to unequivocally identify genes that are activated, or in some way regulated, by gravity. This knowledge can have an impact on practical agronomic purposes, e.g. architecture of root and shoot systems as well as realizing this potential for regulating plant growth in space. Significant interest and support from industry is demonstrated, especially in the analytical genomic sector. The project will use state-of-the-art tools to evaluate the architecture of these pathways. Using DNA microchips and other molecular genetic technology we will gain new quantitative and qualitative information on gravity-regulated gene expression.
The experiments will study the well-known flowering plant, Arabidopsis thaliana, also known as mouse-ear cress or thale cress, a plant which is genetically related to soybeans, cotton, vegetables and oil seed crops. A. thaliana has all of the normal plant functions, and has become a useful research model. Some of its advantages are its short life cycle, small size, prodigious seed production, and its small genome of about 110 Mb comprising 25.498 genes.
During the experiments, seeds will be germinated in the experiment unit in the KUBIK incubators under controlled temperature in a centrifuge simulating 1G for reference purposes. After 4-days growth at 1G half of the samples are transferred to microgravity, while the remained stay on the 1 G centrifuge. Samples are fixed 1-hour, 6-hours and 24-hours after transfer with RNAlaterTM to permit subsequent gene analysis. Additional one sample is fixed with formaldehyde for microscopy analysis of the germinated seedlings.
These genes can now be evaluated systematically using micro-array technology. Micro-arrays are miniaturized arrays of small gene fragments, representing almost the entire Arabidopsis genome and attached to solid supports (chips). These chips can, for instance, be used to examine gene activity or to identify gene mutations by hybridizing a fluorescent ADNc sample, representing the transcriptomes of interest, to the sequences on the microarray. After hybridization, the chips are read with high-speed fluorescent detectors. The location and intensity of each spot reveals the identity and amount of each sequence present in the sample. Since almost the entire A. thaliana genome can be analyzed on a single array, genome-wide patterns of gene expression under multiple experimental conditions can easily be obtained, and either qualitatively or quantitatively analyzed.
This technology is used to examine gravity-regulated gene expression in A. thaliana with unprecedented speed and resolution.
Effect of microgravity on genome-wide changes in gene expression pattern in the model plant Arabidopsis was explored in AT-Space experiment. Experimental containers (EC) were specifically manufactured for the experiment. ECs contained two germination chambers, each independently connected with water and fixative chambers for germination activation and fixation, respectively. Activation of seed germination and subsequent fixations were operated on the ISS by a crew member. Prior fixations, ECs were maintained in ISS 1g centrifuge allowing seeds to germinate and to grow for 5 days in the temperature controlled condition in the dark. Exposure to microgravity was performed by removing ECs from the centrifuge for 1h, 6h or 24h following fixation afterwards. Corresponding in flight 1g and ground 1g controls were prepared in parallel. After return of ECs to the PI’s lab, total RNA was extracted and used for DNA microchip arrays. Data analysis of AT-Space samples revealed numerous genes affected by microgravity. Gene network analysis revealed a hormonal cross-talk between auxin, abscisic acid (ABA) and ethylene signaling pathways in meadiating microgravity triggered stress responses, such as osmotic stress and water deprivation and lipid metabolic changes in particular.
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Image of Arabidopsis thaliana plant used in the AT-Space investigation, Image courtesy of ESA.
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