Effects of Weightlessness and Space Environment on Gene Expression of Picea glauca Seedlings

On the dawn of April 5^TH2010, the Space Shuttle Discovery was launched for the STS-131 mission transporting 24 white spruce seedlings produced by somatic embryogenesis (SE) to the International Space Station (ISS). On the ISS four days later, the best six plants of each of three lines were transferred in a root tray that was inserted in the NASA/KSC incubator (ABRS), in the US laboratory, known as Destiny. Meanwhile on Earth, a ground control was set up in a second ABRS unit in the Space Life Science Lab (SLSL) of the Kennedy Space Center. The three SE lines grew for 30 days in a close environment within both incubators and under same temperature, humidity and light conditions but with a different gravity environment. At the end of the experiment, the leading shoot from three plantlets of each line were sampled and pooled in a Kennedy Space Center Fixation Tube containing a RNA stabilisation solution.

Transcript levels were determined by qPCR for 27 candidate and three reference genes, on 9 seedlings from three lines, grown in each environment. About two-thirds of the 27 genes accumulated a larger number of transcript molecules in microgravity. Three genes varied significantly (t-test, p<0.05) between the two environments and all of them were up‑regulated in microgravity conditions. Based on their sequence similarity, they were annotated against the TAIR10 database. The loci involved are a Hop3 (stress-inducible protein, putative),  a ZPR1 zinc-finger domain protein and  a glutathione S-transferase, C-terminal-like; translation elongation factor EF1B/ribosomal protein S6.