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Arsenic Stress Resistance in the Endophytic Fungus Cladosporium cladosporioides: Physiological and Transcriptomic Insights into Heavy Metal Detoxification

Summary

Researchers discovered a special fungus called Cladosporium cladosporioides living inside the roots of Gentiana yunnanensis, a traditional Chinese medicinal herb. This fungus is remarkably good at tolerating and neutralizing arsenic, a toxic heavy metal found in contaminated soils. The fungus uses multiple strategies to protect itself from arsenic damage, including moving the arsenic to its cell walls, converting it into less toxic forms, and activating protective defense systems.

Background

Heavy metal contamination, particularly arsenic, poses significant risks to medicinal plants and human health. Endophytic fungi isolated from plant roots exhibit remarkable heavy metal tolerance and accumulation capabilities. This study focuses on understanding arsenic detoxification mechanisms in an endophytic fungus isolated from Gentiana yunnanensis, a traditional Chinese medicinal herb grown in arsenic-contaminated soils.

Objective

To identify and characterize an arsenic-tolerant endophytic fungus isolated from Gentiana yunnanensis roots, determine its taxonomic classification, and elucidate the physiological and molecular mechanisms underlying its arsenic resistance and detoxification capabilities.

Results

The fungus was identified as Cladosporium cladosporioides with exceptional arsenic tolerance (EC50: 2051.94 mg/L). The fungus accumulated 1112.64 μg/g total arsenic with 76.64% converted to organic arsenic and 2.24% to As(III). Arsenic was predominantly sequestered in cell walls (4.06 times higher than non-cell wall fraction). Under As(V) stress, antioxidant systems were significantly activated including SOD (96.94% increase), MT (454.78% increase), and GSH (224.84% increase). Transcriptomic analysis identified 4771 differentially expressed genes with 2527 upregulated, including key arsenic-responsive genes (CcArsH_1, CcARR_1, CcARR_3, CcGST_1, CcGST_3).

Conclusion

Cladosporium cladosporioides employs a multi-faceted arsenic detoxification strategy combining subcellular distribution to cell walls, reductive transformation of As(V) to As(III) and organic forms, enhanced antioxidant system activation, and coordinated transcriptomic adaptations. These findings demonstrate the fungus’s potential for arsenic bioremediation and provide insights into arsenic accumulation mechanisms in medicinal plants.
  • Published in:Journal of Fungi (Basel),
  • Study Type:Original Research Study,
  • Source: PMID: 40422708
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