RD22 as a potential rice variety for space exploration: Investigation the impact of a clinostat-simulated microgravity on seed germination across commercial rice varieties

Abstract

Rice is considered crucial for space farming due to its high caloric content and ability to provide a staple food source, and because it can be genetically modified to optimize growth in controlled environments, making it suitable for the closed-loop life support systems necessary in space habitats. This study explores the viability of cultivating commercial rice varieties in microgravity environments, an essential consideration for space agriculture. We employed a 3-dimensional-clinostat to simulate microgravity conditions and observed the germination process with protein changes of five rice varieties: RD22, RD61, PTT1, KDML105, and RD81. The maximal germination percentage (max-GP) was found to be statistically similar across all varieties. Notably, under microgravity, RD22 and RD61 showed increased malondialdehyde (MDA) levels, suggesting enhanced oxidative stress. Proteomic analysis, conducted through 10plex-TMT experiments, revealed a balanced ratio of up- and down-regulated proteins in RD22 and RD61. Contrastingly, PTT1, KDML105, and RD81 predominantly showed protein down-regulation. Remarkably, RD22 demonstrated up-regulation of proteins associated with translation factors and cellular differentiation, suggesting a robust adaptive response. Furthermore, the gibberellin (GA3) level in RD22 significantly increased under microgravity compared to normal gravity, potentially contributing to its superior germination and promising growth prospects. Our findings position RD22 as a favorable candidate for space farming, owing to its germination resilience in microgravity and potential for higher yields. This research lays the groundwork for future studies focused on optimizing RD22 cultivation for extraterrestrial agriculture, potentially expanding the horizons of crop production beyond Earth.