RNA-Seq transcriptome analysis of reactive oxygen species gene network in Mizuna plants grown in long-term space flight

Space environment is suspected to generate reactive oxygen species (ROS) and induce oxidative stress in plants however little is known about the gene expression of ROS gene network in plants grown in long-term space flight. RNA-Seq was used to define the large-scale gene expression profiles of Mizuna harvested after 27 days cultivation in the international space station to understand the molecular response and adaptation to space environment.Results: Total reads of transcripts from the Mizuna grown in the international space station as well as on the ground by RNA-Seq using next generation sequencing technology showed 8,258 and 14,170 transcripts up- and down-regulated in the space-grown Mizuna respectively when compared with those from the ground-grown Mizuna. A total of 20 in 32 ROS oxidative marker genes were up-regulated including high expression of 4 hallmarks and preferentially expressed gene associated with ROS-scavenging genes was thioredoxin glutaredoxin and alternative oxidase genes. In the transcription factors of ROS gene network MEKK1-MKK4-MPK3 OXI1-MKK4-MPK3 and OXI1-MPK3 of MAP cascades induction of WRKY22 by MEKK1-MKK4-MPK3 cascade induction of WRKY25 and repression of ZAT7 by Zat12 were suggested. RbohD and RbohF genes were up-regulated preferentially in NADPH oxidase genes which produce ROS.Conclusions: Our large-scale transcriptome analysis demonstrated that the space environment induced oxidative stress and ROS gene network was activated in the space-grown Mizuna some of which were common genes up-regulated by abiotic and biotic stress and were preferentially up-regulated genes by the space environment even though Mizuna grew in the space as well as on the ground showing that plants could acclimate to the space environment by reprograming the expression of ROS gene network.