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

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 of P. notoginseng seeds. Among the identified plant hormone metabolites, exogenous GA3 results in an increased level 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. Weighted gene co-expression network analysis (WGCNA) revealed that GA3 treatment 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) and Pectinesterase (PME). Conclusions Exogenous GA3 application promotes germination and shorts the after-ripening process 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 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.

A genome-wide survey of DNA methylation inPanax notoginsengreveals CHH hyper-methylation regulates the after-ripening and dormancy of recalcitrant seeds

“…The seeds were placed in a ventilated net basket for 50 days in a sandy stratification chamber (15 ± 5℃). Based on the previous morphological descriptions(Ge et al ., 2023), seeds at three different after-ripening processes (CK, seeds harvested, 0 days after-ripening (DAR); T1, seed morphology completely developed, 30 DAR; T2, seed dormancy released, 50 DAR) were collected and dissected (Fig. 1).…”

“…Using the same scheme described for RNA-Seq, total RNA was isolated from seeds of P. notogensing samples. First-strand cDNA synthesis and real-time PCR were performed according to the method suggested by Jia et al .(2023). The internal control was GAPDH ( GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE )(Ge et al ., 2023) and the 2 -ΔΔCT method(Livak & Schmittgen, 2001) was used to calculate relative expression values.…”

“…First-strand cDNA synthesis and real-time PCR were performed according to the method suggested by Jia et al .(2023). The internal control was GAPDH ( GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE )(Ge et al ., 2023) and the 2 -ΔΔCT method(Livak & Schmittgen, 2001) was used to calculate relative expression values. Primers used in this analysis are listed in Table S9.…”

“…It has been shown that an incompletely developed embryo could be the main reason for the dormancy of P. notoginseng seeds, and the embryo at a heart-shaped period has to be further differentiated and developed during the after-ripening process(Yang et al ., 2018). Exogenous GA 3 application could change the ratio of GA and ABA, and thus greatly facilitate the development of the embryo in recalcitrant P. notoginseng seeds(Ge et al ., 2023). Likewise, the DNA methylation inhibitor, 5-azacytidine, might promote P. notoginseng fruit ripening and seed germination, thus suggesting that DNA methylation indeed regulates seed development and after-ripening-related biological processes(Huang et al ., 2022).…”

Effects of exogenous GA3 and warm water on dormancy breaking germination characteristics of Eucommia ulmoides

“…Seed germination is closely related to changes in the content of endogenous hormones. Various hormones in seed can induce the decomposition and synthesis of storage substances and eventually cause seed germination (Ge et al, 2023). Endogenous GA3 accelerates the decomposition and synthesis of internal materials by increasing various enzyme activities, thereby promoting seed germination (Wang et al, 2020).…”