Experimentation on the International Space Station has reached the stage where repeated and nuanced transcriptome studies are beginning to illuminate the structural and metabolic differences between plants grown in space compared to plants on the Earth. Genes that are important in setting up the spaceflight responses are being identified; their role in spaceflight physiological adaptation are increasingly understood and the fact that different genotypes adapt differently is recognized. However the basic question of whether these spaceflight responses are required for survival has yet to be posed and the fundamental notion that spaceflight responses may be non-adaptive has yet to be explored. Therefore the experiments presented here were designed to ask if portions of the plant spaceflight response can be genetically removed without causing loss of spaceflight survival and without causing increased stress responses. The CARA experiment compared the spaceflight transcriptome responses of two Arabidopsis ecotypes Col-0 and WS as well as that of a PhyD mutant of Col-0. When grown with the ambient light of the ISS phyD displayed a significantly reduced spaceflight transcriptome response compared to Col-0 suggesting that altering the activity of a single gene can actually improve spaceflight adaptation by reducing the transcriptome cost of physiological adaptation. The WS genotype showed an even simpler spaceflight transcriptome response in the ambient light of the ISS more broadly indicating that the plant genotype can be manipulated to reduce the transcriptome cost of plant physiological adaptation to spaceflight and suggesting that genetic manipulation might further reduce or perhaps eliminate the metabolic cost of spaceflight adaptation. When plants were germinated and then left in the dark on the ISS the WS genotype actually mounted a larger transcriptome response than Col-0 suggesting that the in-space light environment affects physiological adaptation which further implies that manipulating the local habitat can also substantially impact the metabolic cost of spaceflight adaptation.

This experiment compared the spaceflight transcriptomes of four commonly used natural variants (ecotypes) of Arabidopsis thaliana using RNAseq. In nature Arabidopsis is a native of Europe/Asia/Northwestern Africa and is found across the globe growing in a wide range of environments. The geographical spread of these various populations has led to a slow divergence leading to distinct ecotypes. Understanding the impact of this ecotypic variability is an important factor when using Arabidopsis as a model. Seeds of the ecotypes Col_0 Ler-2 Ws-2 and Cvi-0 were flown to the International Space Station as part of CRS-4 mission in the Biological Research in Canister (BRIC) hardware. The seeds were germinated on orbit grown for 8 days and then fixed in RNAlater and frozen in the MELFI freezer for return to Earth. Once returned RNA was isolated and RNAseq performed to catalog the transcriptional patterns of the plants grown in space. An identical set of samples were grown in parallel on the ground to provide controls to allow assessment of transcriptional changes specifically associated with the spaceflight environment. This data release includes 48 out of 56 sample expression files with the remaining 8 files to be released at a later date.

This experiment compared the spaceflight transcriptomes of four commonly used natural variants (ecotypes) of Arabidopsis thaliana using RNAseq. In nature Arabidopsis is a native of Europe/Asia/Northwestern Africa and is found across the globe growing in a wide range of environments. The geographical spread of these various populations has led to a slow divergence leading to distinct ecotypes. Understanding the impact of this ecotypic variability is an important factor when using Arabidopsis as a model. Seeds of the ecotypes Col_0 Ler-2 Ws-2 and Cvi-0 were flown to the International Space Station as part of CRS-4 mission in the Biological Research in Canister (BRIC) hardware. The seeds were germinated on orbit grown for 8 days and then fixed in RNAlater and frozen in the MELFI freezer for return to Earth. Once returned RNA was isolated and RNAseq performed to catalog the transcriptional patterns of the plants grown in space. An identical set of samples were grown in parallel on the ground to provide controls to allow assessment of transcriptional changes specifically associated with the spaceflight environment. This data release includes 48 out of 56 sample expression files with the remaining 8 files to be released at a later date.

Experimentation on the International Space Station has reached the stage where repeated and nuanced transcriptome studies are beginning to illuminate the structural and metabolic differences between plants grown in space compared to plants on the Earth. Genes that are important in setting up the spaceflight responses are being identified; their role in spaceflight physiological adaptation are increasingly understood and the fact that different genotypes adapt differently is recognized. However the basic question of whether these spaceflight responses are required for survival has yet to be posed and the fundamental notion that spaceflight responses may be non-adaptive has yet to be explored. Therefore the experiments presented here were designed to ask if portions of the plant spaceflight response can be genetically removed without causing loss of spaceflight survival and without causing increased stress responses. The CARA experiment compared the spaceflight transcriptome responses of two Arabidopsis ecotypes Col-0 and WS as well as that of a PhyD mutant of Col-0. When grown with the ambient light of the ISS phyD displayed a significantly reduced spaceflight transcriptome response compared to Col-0 suggesting that altering the activity of a single gene can actually improve spaceflight adaptation by reducing the transcriptome cost of physiological adaptation. The WS genotype showed and even simpler spaceflight transcriptome response in the ambient light of the ISS more broadly indicating that the plant genotype can be manipulated to reduce the transcriptome cost of plant physiological adaptation to spaceflight and suggesting that genetic manipulation might further reduce or perhaps eliminate the metabolic cost of spaceflight adaptation. When plants were germinated and then left in the dark on the ISS the WS genotype actually mounted a larger transcriptome response than Col-0 suggesting that the in-space light environment affects physiological adaptation which further implies that manipulating the local habitat can also substantially impact the metabolic cost of spaceflight adaptation. CARA Seed Lines and Planting: Three seed lines Wild-Type Wassilewskija (Ws) Columbia-0 (Col-0) and Col-0 PhyD (phyD) Mutants were tested for viability sterility and ability to maintain dormancy before the launch. Tested batches of seeds were planted on phytagel plates as one genotype per plate for gene expression analysis in replicates of three. One set was planted for the flight and one for ground control. The plates were wrapped such that every surface of the plate was covered by two layers of Duvetyn Black-Out cloth (Seattle Fabrics) (Sng et al 2014). The plates were stored 4 xb0 C until launch and was then launched in a cold-stow bag to maintain the plates at 4 xb0 C until integration and activation on the ISS. On Orbit Operations and harvest: The dormant plates were activated on station by removing the Black-Out cloth wrapping 12 days after launch. The plates were then placed on a fabric that was mounted in the US Laboratory module on the wall adjoining the MELFI freezer and secured using Velcro. The plants were allowed to grow on orbit for 11 days; some in the ambient light of ISS and some in the dark. The dark-grown plates were first activated by exposing the seeds to light for 4 hours and then re-wrapped in Black-Out cloth for the duration of the growth period. A corresponding set of seedlings were grown as ground control in KSC. At 11 days seedlings were photographed harvested into KFT containing RNAlater solutions and returned for post-flight analysis. All plates were harvested into KFTs with their counterpart (e.g. Light 1 was harvested with Dark 1). Once the plants were placed in the KFTs the KFT was actuated with RNAlater to preserve the sample. At 24 hours post-harvest KFTs were then transferred to MELFI the -32 xb0C freezer. Following SpaceX-3 splashdown in the Pacific Ocean the KFTs transferred to the Cold Stowage charter plane at