GmAOC4 modulates seed germination by regulating JA biosynthesis in soybean

An allene oxide cyclase 4, GmAOC4, was determined by GWAS and RT-PCR to be significantly associated with seed germination in soybean, and regulates seed germination by promoting more JA accumulation. The seed germination phase is a critical component of the plant lifecycle, and a better understanding of the mechanism behind seed germination in soybeans is needed. We used a genome-wide association study (GWAS) to detect a GWAS signal on chromosome 18. In this GWAS signal, SNP S18_56189166 was located within the 3'untranslated region of Glyma.18G280900, which encodes allene oxide cyclase 4 (named GmAOC4). Analysis of real-time PCR demonstrated that expression levels of GmAOC4 in the low-germination variety (KF, carrying SNP S18_56189166-T) were higher than in the high-germination variety (NN, carrying SNP S18_56189166-C). In these two varieties, KF showed a higher JA concentration than NN at 0 and 24 h after imbibition. Moreover, the overexpression of GmAOC4 led to an increase in the concentration of jasmonic acid (JA) in soybean hairy roots and Arabidopsis thaliana. Furthermore, it was found that GmAOC4-OE lines showed less seed germination than the wild type (WT) under normal conditions in Arabidopsis. After 7 days of ABA treatment, transgenic lines exhibited lower seed germination and higher expression levels of AtABI5 compared with WT, indicating that the overexpression of GmAOC4 resulted in hypersensitivity to ABA. Our findings demonstrate that GmAOC4, which promotes more JA accumulation, helps to regulate seed germination in soybeans.