Promoter Methylation Profiling of Nutrient Assimilation (SulP) and Detoxification (ArsB) Genes in Galdieria SulPhuraria from Taftan Volcanic Springs

Document Type : Original Article

Authors

1 Dept. of Biology, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran

2 M.Sc graduate in Biochemistry, Dept. of Biology, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran.

Abstract

Poly-extreme environments, such as the Taftan volcanic complex in Iran, pose unique survival challenges for eukaryotes, requiring precise genomic regulation to balance nutrient acquisition with heavy metal detoxification. While Horizontal Gene Transfer (HGT) provides the genetic toolkit for adaptation in the red microalga Galdieria sulphuraria, the epigenetic mechanisms governing these acquired genes compared to native loci remain largely unexplored. This study investigates the role of DNA methylation in this adaptation using a "Field vs. Laboratory" de-adaptation model. We analyzed promoter methylation profiles of two functionally contrasting genes in G. sulphuraria, the native high-affinity sulfate permease (SulP) and the horizontally acquired arsenite efflux transporter (ArsB), using bisulfite conversion and targeted Sanger sequencing. Our results reveal a striking epigenetic dichotomy between metabolic and detoxification pathways. The native SulP promoter exhibited robust hypermethylation (72.1%) in field-adapted populations, which significantly decreased to 23.2% (p < 0.0001) under laboratory conditions. This suggests that methylation acts as a dynamic switch to repress sulfate uptake in sulfur-saturated volcanic waters, preventing intracellular toxicity. In contrast, the bacterial-origin ArsB gene maintained a stable, intermediate methylation level (~55–60%) regardless of environmental conditions (p > 0.05). This stability indicates a strategy of "constitutive readiness," ensuring immediate defense against unpredictable arsenic fluctuations. We conclude that G. sulphuraria employs a dual epigenetic strategy: dynamic methylation remodeling for metabolic homeostasis of native genes, and static epigenetic maintenance for essential, HGT-derived detoxification systems.

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Journal of Epigenetics
Volume 6, Issue 2
November 2025
Pages 86-95

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History

  • Receive Date: 02 January 2026
  • Accept Date: 04 January 2026

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