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

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Abstract
Background: Panax notoginseng(Burk) F.H. Chen is an essential plant in the family of Araliaceae. Its seeds are classified as a 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 after-ripening in recalcitrant seeds.Results: In this study, exogenous supply of gibberellic acid (GA3) with different concentrations shortened after-ripening process and promoted the germination ofP. notoginsengseeds. Among the identified plant hormone metabolites, exogenous GA3results in an increased level of endogenous hormone GA3through permeation. A total of 2971 and 9827 differentially expressed genes (DEGs) were identified in response to 50 mg L−1GA3(LG) and 500 mg L−1GA3(HG) treatment, respectively, and the plant hormone signal and related metabolic pathways regulated by GA3was significantly enriched. Weighted gene co-expression network analysis (WGCNA) revealed that GA3treatment enhances GA biosynthesis and accumulation, while inhibiting the gene expression related to ABA signal transduction. 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) andPectinesterase(PME).Conclusions: Exogenous GA3application promotes germination and shorts the after-ripening process ofP. notoginsengseeds by increasing GA3contents 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 recalcitrantP. notoginsengseeds. These findings improve our knowledge of the contribution of GA to regulating the dormancy of MPD seeds during the after-ripening process, and provide new theoretical guidance for the application of recalcitrant seeds in agricultural production and storage.
Funding Information
  • Major Special Science and Technology Project of Yunnan Province (202102AA310048)
  • the National Key Research and Development Plan of China (2021YFD1601003)

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