Transcriptomic analysis of the interaction between FLOWERING LOCUS T induction and photoperiodic signaling in response to spaceflight

Spaceflight has an impact on growth and development of higher plants at both vegetative stage and reproductive stage. A great deal of information has been available on the vegetative stage in space, but relatively little is known about the influence of spaceflight on plants at the reproductive stage. In this study, we constructed a transgenic Arabidopsis thaliana plants expressing flowering control gene, FLOWERING LOCUS T (FT), together with green fluorescent protein gene(GFP) under control of a heat shock-inducible promoter (HSP17.4), by which we induced FT expression inflight through remote controlling heating shock (HS) treatment. Inflight photography data showed that induction of FT expression in plants in space under short-day condition could eliminated the difference of stem length between spaceflight and ground control . Whole-genome microarray analysis of gene expression changes in leaves of wild-type and these transgenic plants grown under the long-day and short-day photoperiod conditions in space indicated that the function of the photoperiod-related spaceflight responsive genes are mainly involved in protein synthesis and post-translation protein modulation, notably protein phosphorylation. In addition, changes of circadian component gene expression in response to spaceflight under different photoperiod indicated that roles of circadian oscillator could act as integrators of spaceflight response and photoperiodic signals in Arabidopsis plants grown in space. Arabidopsis thaliana Columbia (Col-0) ecotype was used as the wild-type (WT) and a transgenic plant expressing FLOWERING LOCUS T (FT) and the reporter gene green fluorescent protein (GFP) under control of a heat shock-inducible promoter (HSP17.4) (pHSP::FT, pHSP::GFP, FG) was constructed. Plants were germinated and grown under long-day (16h light /8h dark, LD) or the short-day (16 h dark/ 8h light, SD) for 20 days prior to flight, then transferred to plant culture box (PCB) flighted with Chinese SJ-10 satellite for 12 days and 15h (launch: 1:38, April 6, 2016; landing: 16:30, April 18, 2016) or keep on ground as control. Temperatures were 22±2°C, relative humidity was between 90% and 100%. The photosynthetically active photon flux density produced by LED lamps was 120 umol.m-2.s-1. Total RNA was extracted from rosette leaves of WT under LD (LW) and under SD (SW) and FG under LD(LG) and under SD (SG) in space (S) and on ground (C), respectively. Each treatment have four rosette leaves and two biological repeat (i.e. S4a, S4b, C4a and C4b).