Metabolomics Analysis in Different Development Stages on SP0 Generation of Rice Seeds After Spaceflight

Abstract

Spaceflight is a special abiotic stress condition. In recent years, it has been confirmed that the spaceflight caused the stress response of rice seeds, and the protein level, transcription level, and methylation level will change during the planting process after returning to the ground. However, the changes at the metabolome level are not very clear. In this study, two kinds of rice seeds, Dongnong423 (DN3) and Dongnong416 (DN6), were carried on the ShiJian-10 retractable satellite (SJ-10) for 12.5 days in orbit, returned to the ground and planted in the field until the three-leaf (TLP) and tillering stage (TS). The results of antioxidant enzyme activity, soluble sugar, and electron leakage rate revealed that the spaceflight caused the stress response of rice. The TLP and TS of DN3 identified 110 and 57 different metabolites, respectively, while the TLP and TS of DN6 identified 104 and 74 different metabolites, respectively. These metabolites included amino acids, sugars, fatty acids, organic acids and secondary metabolites. We used qRT-PCR technology to explore the changes of enzyme genes in the tricarboxylic acid cycle (TCA) and amino acid metabolism pathway. Combined with the results of metabolomics, we determined that during the TLP, the TCA cycle rate of DN3 was inhibited and amino acid metabolism was activated, while the TCA cycle rate of DN6 was activated and amino acid metabolism was inhibited. In TS, the TCA cycle rate of DN3 was inhibited, and amino acid metabolism was not significantly changed, while the TCA cycle rate of DN6 was activated and amino acid metabolism was inhibited. These results suggested that the response mechanisms of the two different rice strains to spaceflight stress are different, and these differences may be reflected in energy consumption and compound biosynthesis of rice in different growth and development stages. This study provided new insights for further exploring the effects of spaceflight.

The Memory of Rice Response to Spaceflight Stress: From the Perspective of Metabolomics and Proteomics

“…Pyridoxine was reduced in TLS but was accumulated in TS ( Figure S11B ). This was somewhat different from the expression patterns of these two compounds in contemporary rice after spaceflight as we reported earlier [ 13 ]. Although offspring rice inherits the effects of spaceflight, it responds in a different way than contemporary rice.…”

“…In addition, glucose was the main product of photosynthesis, and the consumption of glucose indicated that photosynthesis may be reduced [ 53 ]. In our previous study, we also confirmed the changes in these sugars in parent rice after spaceflight [ 13 ]. These results indicated that sugar metabolism was also the main way to respond to spaceflight and can be remembered.…”

“…Therefore, the changes in rice epigenetics and protein synthesis rate after spaceflight may be related to the changes in the magnetic field and the chromatin condensation process during spaceflight. Our previous research results have shown that spaceflight has an impact on contemporary rice’s energy metabolism, amino acid metabolism, sugar metabolism, signal transduction processes, etc., and confirmed that this effect was triggered by ROS [ 11 , 12 , 13 ]. The differences in epigenetic regulation of gene expression induced by environmental stress exposure can continue to the next generation of stressed plants [ 14 ].…”

“…Oxidative stress was the main factor that causes rice to respond to spaceflight. Rice adapted to the effects of spaceflight by regulating amino acid metabolism, protein synthesis and degradation, protein processing, energy metabolism, and sugar metabolism [ 11 , 12 , 13 ]. At present, studies have confirmed that the effects of spaceflight on organisms were heritable, which was caused by the instability of the organism’s genome due to radiation and microgravity.…”

“…Our previous work has observed the effects of spaceflight on the metabolism of cofactors and vitamins in the parent rice [ 13 ]. Nicotinamide can induce plant stress and defense-related metabolic processes.…”