Effects of low temperature on energy metabolism during germination of foxtail millet (Setaria italica L.) seeds

Low-temperature stress significantly hinders the germination of foxtail millet (Setaria italica. L) seeds, posing a major limitation to their production. In this study, we conducted physiological and transcriptomic analyses on seeds from the low-temperature-tolerant variety JG and the low-temperature-sensitive variety CN during the initial 48 h of germination. Our results demonstrated that low-temperature exposure led to a reduction in germination rates by 19.33% for JG and 28.67% for CN. Transcriptomic analysis revealed that the differentially expressed genes were primarily associated with pathways involved in starch and sucrose metabolism, glycolysis, the tricarboxylic acid cycle, oxidative phosphorylation, and plant hormone signal transduction. Research indicates that at low temperatures, the expression levels of genes encoding key enzymes involved in sugar metabolism and oxidative phosphorylation in JG are elevated. This results in pyruvate kinase (PK) and cytochrome C oxidase (CCO) activities being increased by 14.58%-64.94% and 16.95%-120.12%, respectively, compared to CN. Ultimately, the ATP content in JG is 91.30%-120.03% higher than that in CN. Furthermore, the expression levels of genes and transcription factors involved in the biosynthesis and signal transduction of plant hormones, such as auxin (IAA) and cytokinins (CTK), are significantly elevated in JG at low temperatures relative to CN. In summary, JG enhances its cold resistance during the germination period by modulating energy metabolism and hormone balance.