Using multi-omics approach to investigate the effect of a moon soil simulant on Vigna radiata seedling root and shoot growth, stress responses, and photosynthesis

The Moon’s first habitats with a support system and semi-permanent lunar settlement are projected for the 2030s. Growing plants for a food supply is one of the most important factors supporting human life on the Moon. A Moon soil simulant was used in this study as a simulation of the use of available resources on the Moon and a representation of one of the possible alternatives to Moon agriculture. A few studies present the effect of Moon soil simulant on plant growth; however, no study has shown the effect of Moon soil simulant on physiology, proteome, and metabolome simultaneously. Effect of a Moon soil simulant on Vigna radiata seedling growth, physiology, proteins, and metabolites, both in the shoot and root parts were observed. V. radiata seedlings were grown on a Moon soil simulant and Earth soil, as a control, under the same environmental conditions. Vigna radiata seedlings grown on the Moon soil simulant showed no significant difference in shoot height, shoot biomass, or shoot water content compared to the control. However, water stress metabolites, L-proline and kaempferol, were higher. Stress response proteins and metabolites related to jasmonic acid (JA) biosynthesis were also higher, which might be due to the increase of malondialdehyde (MDA) in shoots and reduced chlo- rophyll content. The shoot also had reduced PS II activity (Fv/Fm) and downregulation of proteins related to carbon and energy metabolism. Vigna radiata seedlings grown on the Moon soil simulant showed downregulated lipoxygenase (LOX) proteins that might affect the maintenance of MDA at a certain level in roots and the lower expression of glutathione, superoxide dismutase (SOD), and peroxidase. Jasmone and epi-jasmonic acid were lower compared to the control, which might affect the downregulation of proteins related to stress response in roots and proteins related to the biosynthesis of stress secondary metabolites. The higher expression of aqua- porins may have contributed to maintaining the root water content compared to the control. In addition, the low N content in the Moon soil simulant might induce the upregulation of proteins related to root elongation as a foraging strategy, resulting in increased root length and root biomass compared to the control. Interestingly, formononetin, which has a role in arbuscular mycorrhiza fungi (AMF) colonization and nodule primordia organogenesis by symbiotic soil bacteria, was found to be higher in root seedlings grown on the Moon soil simulant. This study provides a deeper understanding of the effect of Moon soil simulant on a plant at early growth stages as basic knowledge to support future Moon agriculture.