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Could Horizontal Gene Transfer Explain 5S rDNA Similarities Between Frogs and Worm Parasites?
Kaleb Pretto Gatto1,2, Cintia Pelegrineti Targueta3, Stenio Eder Vittorazzi4
1Laboratório de Estudos Cromossômicos, Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas, Campinas 13083-863, São Paulo, Brazil.
Biomolecules
|July 29, 2025
Summary
Horizontal gene transfer (HGT) may occur between eukaryotes. Researchers found evidence of HGT of 5S ribosomal DNA (rDNA) from Xenopus frogs to their flatworm parasite, Protopolystoma xenopodis.
Area of Science:
- Molecular Biology
- Genetics
- Evolutionary Biology
Background:
- Horizontal gene transfer (HGT) is common in prokaryotes but its role in eukaryotes is less understood.
- The 5S ribosomal DNA (rDNA) is a key component of ribosomes and plays a crucial role in protein synthesis.
- Understanding HGT in eukaryotes can shed light on genome evolution and biodiversity.
Purpose of the Study:
- To investigate a potential cross-phylum horizontal gene transfer (HGT) event involving 5S ribosomal DNA (rDNA).
- To determine if 5S rDNA sequences from Xenopus laevis could have been transferred to its parasite Protopolystoma xenopodis.
- To explore the contribution of HGT to the diversity of 5S rDNA families in eukaryotes.
Main Methods:
- Phylogenetic analysis using maximum likelihood to compare gene trees with species trees.
- Sequence divergence analysis of the 5S rDNA gene region and its non-transcribed spacer.
- Examination of the Protopolystoma xenopodis genome assembly for potential contamination with frog DNA.
Main Results:
- A 5S rDNA sequence from Protopolystoma xenopodis showed high similarity to Xenopus laevis 5S rDNA.
- Phylogenetic analysis revealed that the 5S rDNA sequence from Pr. xenopodis clustered with anuran sequences, indicating incongruence with species trees.
- Sequence divergence analyses supported an HGT event from Xenopus to Pr. xenopodis, with no evidence of genome assembly contamination.
Conclusions:
- The study provides strong evidence for a horizontal gene transfer (HGT) of 5S rDNA from Xenopus frogs to their parasitic flatworm Protopolystoma xenopodis.
- This finding suggests that HGT may play a more significant role in shaping eukaryotic genomes and driving genetic diversity than previously recognized.
- The results highlight the potential for cross-phylum gene transfer and its implications for evolutionary biology.
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