Advanced Plant EXperiments 02-1 (APEX-02-1) - 12.03.13
Science Objectives for Everyone
APEX-02-1 continues a highly successful investigation into the effects of microgravity on the development of roots and cells on plant seedlings. The experiment photographs seedlings of arabadopsis, or thale cress, every two hours as they grow in petri dishes. After 14 days the seedlings are preserved for return to Earth and detailed analysis.
Science Results for Everyone
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration
September 2013 - March 2014Expeditions Assigned
37/38Previous ISS Missions
APEX-02-1 will build upon the previously flown Biological Research in Canisters (BRIC)-16 experiment which flew on STS-131.
- Despite decades of research, many of the molecular mechanisms by which gravity regulates plant development remain poorly understood. It is likely that in addition to gravitropism, a number of fundamental plant developmental processes that are influenced by gravity have yet to be discovered.
- The goal of the APEX-02-1 research is to utilize the unique microgravity environment provided by the ISS and the model plant Arabidopsis thaliana to uncover novel pathways that orchestrate the complex cellular processes by which gravity shapes plant development.
The hope is that knowledge gained from this research will also translate into a deeper mechanistic understanding of molecular pathways that govern root growth and cell wall development, which in turn will benefit agricultural practices and bioenergy research on Earth.
The overall goal of APEX-02-1 is to uncover the underlying molecular mechanisms by which microgravity impacts cell wall architecture in the model plant Arabidopsis thaliana using the ABRS housed on the ISS. This research builds on a robust dataset from BRIC-16, which flew on STS-131. Through experiments with the BRIC hardware the science team discovered that spaceflight had a profound influence on the expression of genes involved in regulating cell wall architecture. This led to a hypothesis that plants respond to microgravity in large part through the transcriptional reprogramming of genes that control cell wall remodeling. Because of the prominent root developmental phenotypes (i.e. primary root skewing and inhibition of root hair growth) that were observed in the BRIC-16 experiment, it appears that microgravity-dependent changes in cell wall-related transcripts are predominantly manifested in roots. Furthermore, because primary root and root cell wall ultrastructural defects were most pronounced in a mutant to a vegetative actin isoform (act2), it is hypothesized that microgravity predominantly affects genes that lie within signaling networks linking the actin cytoskeleton with the plant extracellular matrix. Given the successful experiments with BRIC-16, the science team is in an excellent position to effectively utilize the unique capabilities of the ABRS hardware on the ISS to test the aforementioned hypotheses.
A new algorithm was developed from the BRIC-16 experiments and will be utilized here. The algorithm will allow the science team to quantify root growth behavior of wild-type and a higher order vegetative actin mutant (act2 act8 double mutant). This will clarify the extent of actin involvement in specifying root orientation and cell wall remodeling in space. Through the use of monoclonal antibodies and immunocytochemistry, the science team will also determine how the distribution and abundance of specific cell wall components change in microgravity, and correlate such changes with root developmental responses and modifications in gene expression.
Finally, more sensitive deep sequencing technologies (e.g. RNA-Seq) will be employed to discover novel microgravity-induced transcriptional changes in plants. Knowledge from these spaceflight studies will then be translated into corresponding gene functional studies (e.g. mutant analysis and overexpression), which the science team expects will lead to the discovery of new players that modulate root development on earth and in microgravity.
The role of gravity in regulating plant development, especially seedlings, remains poorly understood, and scientists expect that molecular pathways related to gravity remain undiscovered. Experiments on the STS-131 space shuttle mission showed that microgravity has a profound influence on genes that regulate cell wall development. Understanding these pathways will help guide genetic engineering of plants to support long-term space missions and planetary exploration.
Understanding the molecular and genetic mechanisms that control plant development will help provide fundamental tools for improving agricultural and bioenergy research on Earth. It will help in designing crops that use resources more efficiently.
- Time between launch and installation into ABRS GFP Imager: 7-12 days
Experiment run duration: 14 days
- Harvest of one plate after 7 days
- Time between harvest and MELFI insertion: ≥ 24 hours
- Downlink of images required daily
- Harvest photos required; request live video of harvest operations when possible
- Only the Water Refill Kit and KFTs return
ABRS will be prepared for the APEX-02-1 experiment by filling the ABRS water reservoir and installing the ABRS Air Filter Cartridge. Six petri plates will be removed from Cold Stowage and transferred to the ABRS GFP Imager. White light images will be recorded every two hours and downlinked on a daily basis. After an experiment duration of 7 days, GFP Imager will be removed from ABRS and transferred to the Maintenance Work Area for the harvest activity. The imaged petri plate will be removed from the GFP Imager and the remaining five petri plates will remain installed in the GFP Imager and transferred back to ABRS. The imaged petri plate will be photographed and harvested. The harvest activity will require the crewmember to use forceps to pull the plants from the agar surface on the petri plate. The plants will be placed into two KFTs and actuated to deliver the Glutaraldehyde chemical preservative to the plants. The KFTs will be transferred to +4°C in MELFI. After an experiment duration of 14 days, the GFP Imager will again be removed from ABRS and transferred to the Maintenance Work Area for the final harvest activity. Two Glutaraldehyde KFTs and eight RNALater KFTs will be used to harvest the five remaining petri plates. The two additional Glutaraldehyde KFTs will be transferred to +4°C and the eight RNALater KFTs will be transferred to -80°C in MELFI. At the conclusion of the second harvest, a second APEX-02 experiment (APEX-02-2) will be installed into ABRS. The Water Refill Kit will return at ambient and the KFTs will return at +4°C (Glutaraldehyde) and -20°C (RNALater).
Ground Based Results Publications
Hou G, Kramer VL, Wang Y, Chen R, Perbal G, Gilroy S, Blancaflor E. The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinisation of the columella cytoplasm and a persistent lateral auxin gradient. Plant Journal. 2004 Jul; 39(1): 113-125.