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Background <p>Actinobacteria of the genus <i>Streptomyces</i> are recognized as prolific producers of bioactive metabolites capable of regulating plant growth and stress responses. However, isolate-level phytohormone data for <i>Streptomyces griseoviridis</i>, a commercially relevant biocontrol species, remain limited and sometimes contradictory.</p> Results <p>A strain of <i>S. griseoviridis</i> was isolated and molecularly characterized. High-performance liquid chromatography (HPLC) of its cell-free culture filtrate (CFF) revealed the presence of gibberellic acid (46.68&#xa0;µg/100 mL), zeatin (18.90&#xa0;µg/100 mL), indole-3-acetic acid (3.93&#xa0;µg/100 mL), and abscisic acid (0.38&#xa0;µg/100 mL), while gas chromatography-mass spectrometry (GC-MS) identified oleic acid (17.1%) and palmitic acid methyl ester (8.34%) as major metabolites. Seeds of <i>Phaseolus vulgaris</i> and <i>Vicia faba</i> were primed with varying concentrations of CFF. In <i>P. vulgaris</i>, the 25% CFF significantly enhanced germination percentage (GP; 66.7% vs. 60.0% control), germination energy (GE; 56.7 vs. 41.7), germination rate index (GRI; 4.02 vs. 3.11), stem length (20.80 vs. 16.10&#xa0;cm), and total photosynthetic pigments (3.79 vs. 2.8&#xa0;mg/g). In <i>V. faba</i>, the 10% CFF proved most effective, achieving 100% GP (control: 98.3%), increasing GE and GRI, reducing mean germination time, and elevating total pigments (3.11 vs. 1.86&#xa0;mg/g). Regarding soluble metabolites, soluble protein content in <i>P. vulgaris</i> was maximized by the 25% and 50% CFF treatments, reaching 165.4 and 136.8&#xa0;mg/g dry weight, respectively, compared to 108.9&#xa0;mg/g in the control, while soluble sugars increased with 10% CFF concentrations. In <i>V. faba</i>, the highest soluble protein concentration (295.4&#xa0;mg/g) was achieved at 10% CFF (control: 202.1&#xa0;mg/g), whereas soluble sugars reached a maximum at 100% CFF. Molecular docking revealed compound 2-acetyl-3-(2-cinnamido)ethyl-7-methoxyindole (indole-related) exhibited strong binding to NCED1 (− 7.85&#xa0;kcal/mol), CCD1 (− 9.21&#xa0;kcal/mol), starch phosphorylase (− 7.03&#xa0;kcal/mol), and AGPase (− 6.56&#xa0;kcal/mol), outperforming controls and fatty acid derivatives.</p> Conclusion <p>The culture filtrate of <i>Streptomyces griseoviridis</i> constituted a biologically active signaling pool capable of modulating legume primary metabolism and photosynthetic pigment profiles in a species- and concentration-dependent manner. This study provided novel isolate-level evidence of the hormonal and metabolic effects of <i>S. griseoviridis</i> filtrates and pointed out the potential of plant growth-promoting <i>Streptomyces</i> species as sustainable drivers of crop productivity and food security.</p>

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Seed priming with Streptomyces griseoviridis culture filtrate: species-specific enhancement of legume germination and seedling vigor through hormonal and metabolic signaling

  • 期刊论文

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  • 发表日期：

    2026年6月23日

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  • Rehab M. Abdelhamid,
  • Asmaa Abdelsalam,
  • Seifeldin Elabed,
  • Heba El-Sayed

摘要

Background

Actinobacteria of the genus Streptomyces are recognized as prolific producers of bioactive metabolites capable of regulating plant growth and stress responses. However, isolate-level phytohormone data for Streptomyces griseoviridis, a commercially relevant biocontrol species, remain limited and sometimes contradictory.

Results

A strain of S. griseoviridis was isolated and molecularly characterized. High-performance liquid chromatography (HPLC) of its cell-free culture filtrate (CFF) revealed the presence of gibberellic acid (46.68 µg/100 mL), zeatin (18.90 µg/100 mL), indole-3-acetic acid (3.93 µg/100 mL), and abscisic acid (0.38 µg/100 mL), while gas chromatography-mass spectrometry (GC-MS) identified oleic acid (17.1%) and palmitic acid methyl ester (8.34%) as major metabolites. Seeds of Phaseolus vulgaris and Vicia faba were primed with varying concentrations of CFF. In P. vulgaris, the 25% CFF significantly enhanced germination percentage (GP; 66.7% vs. 60.0% control), germination energy (GE; 56.7 vs. 41.7), germination rate index (GRI; 4.02 vs. 3.11), stem length (20.80 vs. 16.10 cm), and total photosynthetic pigments (3.79 vs. 2.8 mg/g). In V. faba, the 10% CFF proved most effective, achieving 100% GP (control: 98.3%), increasing GE and GRI, reducing mean germination time, and elevating total pigments (3.11 vs. 1.86 mg/g). Regarding soluble metabolites, soluble protein content in P. vulgaris was maximized by the 25% and 50% CFF treatments, reaching 165.4 and 136.8 mg/g dry weight, respectively, compared to 108.9 mg/g in the control, while soluble sugars increased with 10% CFF concentrations. In V. faba, the highest soluble protein concentration (295.4 mg/g) was achieved at 10% CFF (control: 202.1 mg/g), whereas soluble sugars reached a maximum at 100% CFF. Molecular docking revealed compound 2-acetyl-3-(2-cinnamido)ethyl-7-methoxyindole (indole-related) exhibited strong binding to NCED1 (− 7.85 kcal/mol), CCD1 (− 9.21 kcal/mol), starch phosphorylase (− 7.03 kcal/mol), and AGPase (− 6.56 kcal/mol), outperforming controls and fatty acid derivatives.

Conclusion

The culture filtrate of Streptomyces griseoviridis constituted a biologically active signaling pool capable of modulating legume primary metabolism and photosynthetic pigment profiles in a species- and concentration-dependent manner. This study provided novel isolate-level evidence of the hormonal and metabolic effects of S. griseoviridis filtrates and pointed out the potential of plant growth-promoting Streptomyces species as sustainable drivers of crop productivity and food security.