Keisuke Hitachi

The role of a simulated microgravity environment on soybean growth was investigated. The root grew more under simulated microgravity conditions than in the presence of gravity. However, root shortening due to salt stress did not occur in simulated microgravity conditions. To reveal these mechanisms by simulated microgravity environment on soybean root, a proteomic analysis was conducted. Proteomic analysis revealed that among 1547 proteins, the abundances of proteins related to phytohormone, oxidative stress, ubiquitin/proteasome system, cell organization, and cell wall organization were altered under stimulated microgravity compared with gravity. Membrane-localized proteins and redox-related proteins were inversely correlated in protein numbers due to salt stress under gravity and the simulated microgravity condition. Proteins identified by proteomics were validated for protein accumulation by immunoblot analysis. Superoxide dismutase and ascorbate peroxidases, which are reactive oxygen species-scavenging proteins, increased in soybean root under salt stress but not in the simulated microgravity conditions even under stress. The accumulation of 45 kDa aquaporin and 70 kDa calnexin in soybean root under salt stress were increased in the simulated microgravity conditions compared to gravity. These findings suggest that soybean growth under salt stress may be regulated through improved water permeability, mitigation of reactive oxygen species production, and restoration of protein folding under simulated microgravity conditions.

Wheat is one of the most extensively grown crops in the world; however, its productivity is reduced due to salinity. This study focused on millimeter wave (MMW) irradiation to clarify the salt-stress tolerance mechanism in wheat. In the present study, wheat-root growth, which was suppressed to 77.6% of the control level under salt stress, was recovered to the control level by MMW irradiation. To reveal the salt-stress tolerance mechanism of MMW irradiation on wheat, a proteomic analysis was conducted. Proteins related to cell cycle, proliferation, and transport in biological processes, as well as proteins related to the nucleus, cytoskeleton, and cytoplasm within cellular components, were inversely correlated with the number of proteins. The results of the proteomic analysis were verified by immunoblot and other analyses. Among the proteins related to the scavenging reactive-oxygen species, superoxide dismutase and glutathione reductase accumulated under salt stress and further increased in the MMW-irradiated wheat. Among pathogen-related proteins, pathogenesis-related protein 1 and the Bowman-Birk proteinase inhibitor decreased under salt stress and recovered to the control level in the MMW-irradiated wheat. The present results indicate that MMW irradiation of wheat seeds improves plant-growth recovery from salt stress through regulating the reactive oxygen species-scavenging system and the pathogen-related proteins. These genes may contribute to the development of salt-stress-tolerant wheat through marker-assisted breeding and genome editing.

Salt stress is a serious problem, because it reduces the plant growth and seed yield of wheat. To investigate the salt-tolerant mechanism of wheat caused by plant-derived smoke (PDS) solution, metabolomic and proteomic techniques were used. PDS solution, which repairs the growth inhibition of wheat under salt stress, contains metabolites related to flavonoid biosynthesis. Wheat was treated with PDS solution under salt stress and proteins were analyzed using a gel-free/label-free proteomic technique. Oppositely changed proteins were associated with protein metabolism and signal transduction in biological processes, as well as mitochondrion, endoplasmic reticulum/Golgi, and plasma membrane in cellular components with PDS solution under salt stress compared to control. Using immuno-blot analysis, proteomic results confirmed that ascorbate peroxidase increased with salt stress and decreased with additional PDS solution; however, H+-ATPase displayed opposite effects. Ubiquitin increased with salt stress and decreased with additional PDS solution; nevertheless, genomic DNA did not change. As part of mitochondrion-related events, the contents of ATP increased with salt stress and recovered with additional PDS solution. These results suggest that PDS solution enhances wheat growth suppressed by salt stress through the regulation of energy metabolism and the ubiquitin-proteasome system related to flavonoid metabolism.