Ethylene enhances peanut seed germination by modulating hormonal and metabolic pathways

Ethylene influences various physiological processes especially seed germination in plants. Through this study of ethylene on peanut seed germination, we found that soaking seeds in a 0.2 mM ethylene solution for 12 h, followed by water soaking, optimally promotes germination. To understand the mechanisms involved, we measured abscisic acid (ABA), gibberellins (GA), crude fat, and 18 fatty acids using GC-MS and also analyzed gene expression related to hormone pathways, fatty acid degradation, and cell wall loosening in both control and ethylene-treated seeds. Our results showed that ethylene significantly increased GA3 and GA4 expression levels, induced endogenous ethylene synthesis and signal transduction, and interfered with ABA signaling. Ethylene also enhanced fatty acid degradation and facilitated cell wall loosening. Notably, genes involved in these processes, such as the ethylene synthesis rate-limiting gene <italic>ACO</italic>, the ethylene receptor <italic>ETR</italic>, and cell wall loosening genes <italic>EXP</italic> and <italic>PEC</italic>, were significantly upregulated by ethylene treatment. In contrast, the abscisic acid-insensitive <italic>ABI5</italic> was significantly downregulated after ethylene treatment. Further experiments confirmed that ethylene promoted the expression of three <italic>ERF</italic>s, which could bind to the promoter of <italic>ABI5</italic> and inhibit its expression. This study is also the first to identify ethylene's role in promoting fatty acid degradation in peanut seeds. In conclusion, our findings reveal that ethylene enhances peanut seed germination through hormonal modulation, signal transduction enhancement, and metabolic adjustments. These insights provide a deeper understanding of ethylene's role in seed germination and offer potential applications for improving germination practices in agriculture.