Research On The Molecular Mechanism Of Seed Dormancy Release And Germination Of Panax Quinquefolium L.

American ginseng (Panax quinquefolium L.) is a perennial plant which has a wide range of pharmacological activity and medicinal value. American ginseng is propagated from seed, but the seed has deep dormancy characteristics which need temperature stratification to relesase dormancy. Currently, the molecular mechanisms of American ginseng seed dormancy and germination is not clear.Gibberellin and abscisic acid are the key hormones for controlling the dormancy and germination of seeds. In order to study the fuction of GA and ABA, six kinds of hormones such as Gibberellin A3, Gibberellic acid A4+A7, Abscisic acid, fluridone, paclobutrazol, uniconazole were used to soak American ginseng seeds in the study. Dry seeds were stratification at 20 ℃ while crach seeds were stratification at 4℃. Then embryo rate was calculated every 30d. Then samped at different periods of seed dormancy as initial period, middle period and release period of morphological dormany and physiological dormany to measure endogenous hormones GA and ABA by enzyme-linked immunosorbent assay (ELISA). The study found that after GA3 and GA4+7 treatment physiological ripening time was shorter than control group, and endogenous abscisic acid content in physiological dormancy is less than control group.Through the analysis of transcriptome data,125 genes about plant hormone metabolism and dormancy and germination were designed and analysed by Semi-quantitative PCR. Among these 23 genes showed good specificity, and no or weak expression in the early stage(0 days) of seed stratification. Ten genes about dormancy release hormone such as NCED, ZEP, DELLA, GIGANTE, GA2ox, GA20ox, GA3ox, KAO, CYP707A, DRM were selected out for fluorescence quantitative PCR. The study found that GA biosynthetic genes GA20ox, GA3ox and KAO expression were higher in the period of physiological dormancy than morphological dormancy. After treatment of GA3 and GA4+7 these three biosynthetic genes were less expression than control group.At last, we cloned and analysed the gene PqGA2ox which participates in GA synthetic and the gene PqGA20ox which participates in GA decomposition from American ginseng seeds, and obtained GenBank accession number KJ802836 record and KJ740524. And bioinformatics analysis showed that PqGA2ox and PqGA20ox has neither transmembrane district nor signal peptide.In this study, the expression of the key genes related to plant hormone GA and ABA metabolism and seed dormancy release and germination were analysed to lay the foundation of dormancy and germination mechanism of American ginseng.