Methyl jasmonate enhances seed germination via accelerating lipid mobilization and jasmonate signal amplification in cotton (Gossypium hirsutum L.)

Seed germination is a critical determinant of crop establishment and yield, yet it is often compromised by low vigor and stress sensitivity in cotton. Methyl jasmonate (MeJA), a plant signaling molecule, has emerged as a potential regulator of germination, though its systemic mechanism in oilseeds remains unclear. Here, we demonstrate that treatment with 1 μM MeJA significantly enhances germination and vigor indices in two cotton cultivars (XLZ61 and TH2). MeJA upregulated the activities of key antioxidant enzymes catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) during early seed germination, thereby mitigating oxidative stress. Crucially, MeJA promoted the rapid mobilization of storage lipids by downregulating the oil body structural gene GhOle5 , leading to premature oil body fusion, increased lipase activity, and accelerated triacylglycerol (TAG) degradation. Fatty acid profiling and transcriptomic analysis revealed that MeJA reprogrammed lipid metabolism, enhancing β-oxidation of fatty acids like C18:2 while diverting C18:3 toward jasmonate biosynthesis. This initiated a self-amplifying JA signaling loop, characterized by GhJAZ downregulation, GhMYC2 activation, and upregulated expression of JA synthesis genes ( GhLOX1 , GhAOS , GhAOC1 ). Concurrently, MeJA fine-tuned hormone crosstalk by transiently suppressing the ABA signaling genes GhNCED1 and GhABI5 to alleviate dormancy, while later allowing their recovery for seedling development. Weighted gene co-expression network analysis (WGCNA) further integrated these changes, identifying key modules linking lipid degradation, hormone dynamics, and transcriptional regulation. Our findings reveal that MeJA orchestrates seed germination through a coordinated network involving signal amplification, oil body deconstruction, metabolic flux reprogramming, and hormonal rebalancing. This study provides novel insights into jasmonate function in seed physiology and offers a theoretical basis for hormone-priming strategies to improve seed vigor in cotton and other oil crops.