Ginsenoside from Panax plants rewires root growth by blocking auxin traffic and triggering oxidative stress

Plants of the Panax genus—which includes ginseng and notoginseng—are known to suppress the growth of neighbouring plants through chemical warfare, but the precise molecular weapons and their targets have remained unclear. Now, researchers have identified Zingibroside R1 (ZR1), a rare ginsenoside found in aged and wild Panax species, as a potent allelochemical that inhibits root growth. The study reveals that ZR1 disrupts polar auxin transport, alters auxin distribution in root tips, and triggers oxidative stress responses—ultimately shortening roots and impairing meristem activity through the downregulation of key stem cell regulators.

Continuous cropping of Panax species—medicinal plants valued for their ginsenoside content—often leads to soil sickness, a phenomenon in which the same crop cannot be successfully replanted in the same soil. Allelochemicals released by plant roots into the rhizosphere are major contributors to this problem, yet the molecular mechanisms by which these compounds affect root development have remained largely unexplored. Among the dozens of ginsenosides produced by Panax plants, triterpenoid glycosides have been implicated in autotoxicity, but systematic evaluation of their allelopathic properties and underlying modes of action is still lacking. Based on these challenges, there is a pressing need for in‑depth investigation into how specific ginsenosides interfere with root growth at the cellular and molecular levels.

A multinational research team from Shaanxi University of Chinese Medicine, Hubei University of Medicine, the China Academy of Chinese Medical Sciences, and the Institute of Science and Technology Austria reports (DOI: 10.1093/hr/uhag185) their findings in Horticulture Research in 2026. The study demonstrates that Zingibroside R1 (ZR1), a rare oleanane‑type ginsenoside, inhibits root elongation in both ginseng adventitious roots and Arabidopsis thaliana primary roots by disrupting auxin transport and triggering oxidative stress responses.

The researchers screened twelve ginsenosides and identified ZR1 as the most potent inhibitor of root growth. In ginseng adventitious roots, 100 μM ZR1 reduced root density by 65.9% at 30 days. In Arabidopsis, ZR1 treatment caused a 45.9% reduction in meristem length and a 66.1% decrease in elongation zone length at 10 μM. Using fluorescent reporter lines, the team found that ZR1 suppressed the expression of PIN1, PIN2, and PIN4—genes encoding auxin efflux transporters—within two days of treatment, leading to reduced auxin accumulation in root tips as reported by DR5::GFP. Combination treatments with the auxin transport inhibitor N‑1‑naphthylphthalamic acid (NPA) produced synergistic inhibitory effects, while the aux1 and pin2 mutants showed exacerbated root coiling and shortening phenotypes. Molecular docking and dynamics simulations suggested that ZR1 may bind stably to the auxin receptor TIR1 and the transcription factor ARF7, with binding affinities of −8.4 and −7.2 kcal/mol, respectively. Beyond auxin disruption, ZR1 significantly reduced the expression of root stem cell regulators including PLT1/2, WOX5, SHR, and SCR. Transcriptomic analysis revealed that ZR1 treatment impaired reactive oxygen species (ROS) scavenging by reducing superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, while altering the glutathione (GSH/GSSG) redox balance—disrupting the plant's detoxification capacity.

The authors said that what makes ZR1 particularly interesting is its dual action: it doesn't just interfere with auxin transport like many known allelochemicals do, but it also compromises the plant's antioxidant defence system. “ZR1 essentially hits the root from two directions at once—disrupting the hormonal signals that guide root growth while simultaneously impairing the cellular machinery that normally protects against oxidative damage,” they explained. “This combination may explain why ZR1 exerts such strong inhibitory effects even at relatively low concentrations.”

The findings have significant implications for understanding and managing soil sickness in commercial ginseng cultivation. By identifying ZR1 as a key allelochemical and elucidating its molecular targets, the study provides a mechanistic framework that could inform strategies for crop rotation, soil management, and the development of resistant rootstock varieties. Furthermore, the dual mechanism—targeting both auxin transport and oxidative stress pathways—offers a potential blueprint for designing next‑generation plant growth regulators or herbicides that act through multiple pathways to reduce the risk of resistance development. The research also opens new avenues for investigating how other triterpenoid saponins in Panax and related genera exert their biological effects on root architecture and plant–plant interactions in agricultural and natural ecosystems.

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References

DOI

10.1093/hr/uhag185

Original Source URL

https://doi.org/10.1093/hr/uhag185

Funding information

National Natural Science Foundation of China (82373987); Key project at central government level (2060302‑2501‑02, 2060302‑2401‑08); Fundamental Research Funds for the Central public welfare research institutes (ZZ13‑YQ‑093, ZZXT202508); Scientific and Technological Innovation Project of China Academy of Chinese Medical Sciences (CI2024C007YN); CACMS Innovation Fund (CI2025G00‑06); Joint supported by Hubei Provincial Natural Science Foundation and Shiyan City (2025AFD180); High‑level Key Discipline Construction Project of the National Administration of Traditional Chinese Medicine (zyyzdxk‑2023202).

About Horticulture Research

Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.