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Exogenous L-Arginine Enhances Pathogenicity of Alternaria alternata on Kiwifruit by Regulating Metabolisms of Nitric Oxide, Polyamines, Reactive Oxygen Species (ROS), and Cell Wall Modification

Summary

Researchers discovered that a specific nutrient called L-arginine paradoxically makes a fungus that causes black spot on kiwifruit more dangerous at low concentrations. The fungus uses this amino acid to trigger multiple survival mechanisms including producing protective molecules and enzymes that break down plant cell walls. However, at higher concentrations, L-arginine actually inhibits the fungus, suggesting it could be used as part of a disease control strategy.

Background

Black spot disease caused by Alternaria alternata is a major postharvest disease of kiwifruit causing significant losses. L-arginine is a semi-essential amino acid that plays important roles in fungal metabolism and produces metabolites like nitric oxide and polyamines that regulate pathogenic processes.

Objective

To investigate the effect of exogenous L-arginine on the pathogenicity of A. alternata and the underlying molecular mechanisms involving nitric oxide, polyamine, reactive oxygen species, and cell wall-degrading enzyme regulation.

Results

5 mM L-arginine significantly promoted spore germination (25.9% higher), increased colony and lesion diameter (23.1% and 9.3% respectively), and induced accumulation of endogenous arginine, polyamines, and nitric oxide. Treatment also triggered ROS production (H₂O₂ 15.9% higher, O₂⁻ 2.2 times higher) and activated antioxidant enzyme activities and cell wall-degrading enzymes.

Conclusion

Exogenous L-arginine enhances A. alternata pathogenicity through multiple signaling pathways involving polyamine synthesis, nitric oxide production, reactive oxygen species generation, and activation of antioxidant and cell wall-degrading enzyme systems. These findings provide a theoretical basis for targeted control strategies of A. alternata on kiwifruit.
  • Published in:Journal of Fungi (Basel),
  • Study Type:Experimental Research,
  • Source: PMID: 39590720, DOI: 10.3390/jof10110801
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