Exogenous gibberellic acid shortening after-ripening process and promoting seed germination in a medicinal plant Panax notoginseng

Abstract

Abstract Background Panax notoginseng (Burk) F.H. Chen is an important medicinal plant in the family of Araliaceae. Its seeds are classified as the type of morphophysiological dormancy (MPD), and are characterized by recalcitrance during the after-ripening process. However, it is not clear about the molecular mechanism on the dormancy in harvested recalcitrant seeds. Results In this study, exogenous supply of gibberellic acid (GA3) with different concentrations shortened after-ripening process and promoted germination of P. notoginseng seeds. Among the identified plant hormone metabolites, exogenous GA3 results in an increased levels of endogenous hormone GA3 through permeation. A total of 2971 and 9827 differentially expressed genes (DEGs) were identified in response to 50 mg L− 1 GA3 (LG) and 500 mg L− 1 GA3 (HG) treatment, respectively, and the plant hormone signal and related metabolic pathways regulated by GA3 was significantly enriched. GA3 treatment upregulated the expression of ent-copalyl diphosphate synthase (CPS), GA 20-oxidase (GA20ox) and GIBBERELLIN INSENSITIVE DWARF1 (GID1), whereas it downregulated DELLA, Pyrabactin resistance 1-like (PYL) and ABA-INSENSITIVE5 (ABI5). This effect was associated with higher expression of crucial seed embryo development and cell wall loosening genes, Leafy Contyledon1 (LEC1), Late Embryogenesis Abundant (LEA), expansins (EXP) and Pectinesterase (PME). Conclusions Exogenous GA3 application promotes the germination of P. notoginseng seeds by increasing GA3 contents through permeation. Furthermore, the altered ratio of GA and ABA contributes to the development of the embryo, breaks the mechanical constraints of the seed coat and promotes the protrusion of the radicle in recalcitrant P. notoginseng seeds. These findings improve our knowledge of the contribution of GA to regulating dormancy of MPD seeds during the after-ripening process, and provide a new theoretical guidance for the application of recalcitrant seeds in agricultural production and storage.