Dataset Information

Nitrate enhances the secondary growth of storage roots in Panax ginseng.

ABSTRACT:

Background

Nitrogen (N) is an essential macronutrient for plant growth and development. To support agricultural production and enhance crop yield, two major N sources, nitrate and ammonium, are applied as fertilizers to the soil. Although many studies have been conducted on N uptake and signal transduction, the molecular genetic mechanisms of N-mediated physiological roles, such as the secondary growth of storage roots, remain largely unknown.

Methods

One-year-old P. ginseng seedlings treated with KNO₃ were analyzed for the secondary growth of storage roots. The histological paraffin sections were subjected to bright and polarized light microscopic analysis. Genome-wide RNA-seq and network analysis were carried out to dissect the molecular mechanism of nitrate-mediated promotion of ginseng storage root thickening.

Results

Here, we report the positive effects of nitrate on storage root secondary growth in Panax ginseng. Exogenous nitrate supply to ginseng seedlings significantly increased the root secondary growth. Histological analysis indicated that the enhancement of root secondary growth could be attributed to the increase in cambium stem cell activity and the subsequent differentiation of cambium-derived storage parenchymal cells. RNA-seq and gene set enrichment analysis (GSEA) revealed that the formation of a transcriptional network comprising auxin, brassinosteroid (BR)-, ethylene-, and jasmonic acid (JA)-related genes mainly contributed to the secondary growth of ginseng storage roots. In addition, increased proliferation of cambium stem cells by a N-rich source inhibited the accumulation of starch granules in storage parenchymal cells.

Conclusion

Thus, through the integration of bioinformatic and histological tissue analyses, we demonstrate that nitrate assimilation and signaling pathways are integrated into key biological processes that promote the secondary growth of P. ginseng storage roots.

SUBMITTER: Geem KR

PROVIDER: S-EPMC10214138 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature

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Nitrate enhances the secondary growth of storage roots in <i>Panax ginseng</i>.

Geem Kyoung Rok KR Kim Jaewook J Bae Wonsil W Jee Moo-Geun MG Yu Jin J Jang Inbae I Lee Dong-Yun DY Hong Chang Pyo CP Shim Donghwan D Ryu Hojin H

Journal of ginseng research 20220602 3

<h4>Background</h4>Nitrogen (N) is an essential macronutrient for plant growth and development. To support agricultural production and enhance crop yield, two major N sources, nitrate and ammonium, are applied as fertilizers to the soil. Although many studies have been conducted on N uptake and signal transduction, the molecular genetic mechanisms of N-mediated physiological roles, such as the secondary growth of storage roots, remain largely unknown.<h4>Methods</h4>One-year-old <i>P. ginseng</i ...[more]

PMID: 37252286

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Project description:The roots and rhizomes of Panax ginseng C.A. Mey are commonly used herbal medicine in Asian countries. These components contain a large number of secondary metabolites known as ginsenosides, which serve as primary active ingredient. Environmental factors significantly influence the production of secondary metabolites, which are crucial for enhancing plant adaptability to ecological stress. P. ginseng is a shady plant that thrives in a constantly humid and temperate environment. However, it cannot withstand excessive moisture, making soil moisture a significant ecological stress affecting P. ginseng survival. In this study, we applied a water spray to maintain a water-saturated surface on 5-year-old fresh P. ginseng roots for a duration of 5 days, to establish a short-term water stress condition. The results revealed a notable increase in superoxide anion (O2·-), hydrogen peroxide (H2O2), and NADPH oxidase (NOX) activity (p < 0.01), as well as malondialdehyde (MDA) contents (p < 0.01) in both the main root and fibrous root of P. ginseng. Additionally, superoxide dismutase (SOD), catalase (CAT), peroxides (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities also elevated significantly under water stress (p < 0.01). Ascorbic acid (AsA), glutathione (GSH) and oxidized glutathione (GSSG) contents also showed a marked increase (p < 0.01). The main root treated with water showed the most positive impact on the 5th day. Water stress boosted the activities of key enzymes including 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), farnesyl pyrophosphate synthase (FPS), squalene synthase (SS), squalene epoxidase (SE), and dammarenediol-II synthase (DS) involved in the ginsenoside biosynthesis pathway (p <0.01). This resulted in a significant an increase in the level of ginsenosides Rg1, Rb1, Rf, Rg2+Rh1, Rc, and Rb3, by 42.4%, 21.0%, 15.7%, 157.9%, 18.3%, and 10.6% respectively, and an increase of 40.1% in total saponins content. Similarly, the fibrous root changes in the treated sample showed the most positive impact on the 4th day. Specifically, Rg1, Re, Rb1, Rf, Rg2+Rh1, Rc, Ro, and Rb2 increased by 41.8%, 20.5%, 17.3%, 84.3%, 30.7%, 35.6%, 8.6%, and 7.6%, respectively, and an increase of 4.2% in total saponins content. Furthermore, 1,3-disphosphoglycerate (1,3-DPG) contents and phosphoenolpyruvate carboxylase (PEPC) activities, which are key intermediate of primary metabolism, were significantly elevated under water stress (p < 0.01). This indicates that the primary source of the raw materials used in the biosynthesis of secondary metabolites is sugars. Pharmacodynamic analysis demonstrated that water stress could increase the contents of ginsenosides, improve the quality of ginseng, and enhance the efficacy of ginseng root to a certain extent.