Flowering of Arabidopsis and Rice in Space

The reproductive success of plants is often dependent on their flowering time being adapted to the territorial environment, in which gravity remains constant. Whether plants can follow the same rule to determine their flowering time under microgravity in space is unknown. Here, a 12-day mission on orbiter Chinese SJ-10 recoverable microgravity experimental satellite (SJ-10 satellite) carried long-day-flowering Arabidopsis thaliana and short-day-flowering rice (Oryza sativa), and transgenic Arabidopsis plants engineered with a transgene composed of a heat shock-inducible promoter (HSP) linked to the green fluorescence protein (GFP) reporter gene and FLOWERING LOCUS T (FT) gene. The plants were used to examined FT gene expression patterns in space to address the effects of microgravity on flowering induction. In addition, application of GFP technique for FT visualization on the SJ-10 satellite in this study is also introduced. Finally, a comprehensive analysis of global gene expression of leaves of Arabidopsis and rice grown in space under a long-day (LD) and a short-day (SD) conditions, respectively, was carried out to understand effects of microgravity on photoperiodic flowering induction at molecular level. Our results showed that microgravity apparently down-regulated expression of GIGANTEA (GI), which is involved in circadian clock functions. Furthermore, possible key points of microgravity responses in the main photoperiod pathways, GI-CO-FT module in Arabidopsis or GI-Hd1-Hd3a module in rice, are also discussed with regard to potential future spaceflight experiment opportunities.