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Structural Organization of S516 Group I Introns in Myxomycetes
Betty M N Furulund1, Bård O Karlsen2, Igor Babiak1
1Genomic Division, Faculty of Biosciences and Aquaculture, Nord University, 8049 Bodø, Norway.
Genes
|June 24, 2022
Summary
Myxomycete group I introns in ribosomal DNA exhibit complex structures and dynamic evolution. These mobile genetic elements show varied organizations and inheritance patterns, including horizontal gene transfer.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Genetics
Background:
- Group I introns are mobile genetic elements with self-splicing ribozyme capabilities.
- In eukaryotes, nuclear group I introns are primarily found in ribosomal DNA of microorganisms.
- Myxomycetes, a unique protist phylum, are notably rich in nucleolar group I introns.
Purpose of the Study:
- To analyze and compare group I introns at position 516 in the small subunit ribosomal DNA of diverse myxomycete taxa.
- To investigate the structural complexity, organization, and evolutionary history of these introns.
Main Methods:
- Comparative analysis of 75 group I introns from various myxomycete species.
- Secondary structure analysis to identify conserved ribozyme cores and sequence complexity.
- Phylogenetic analyses of introns and host genes to infer inheritance patterns.
- Reconstruction of evolutionary trajectories of these genetic elements.
Main Results:
- A conserved group IC1 ribozyme core was identified, alongside significant RNA sequence complexity in peripheral regions.
- Five introns displayed a twintron organization, with a homing endonuclease gene interrupted by a spliceosomal intron.
- Eleven introns featured direct repeat arrays with variable structures, copy numbers, and motif lengths.
- Phylogenetic analyses indicated a complex inheritance pattern involving both vertical and horizontal gene transfer.
Conclusions:
- Myxomycete S516 introns represent a family of genetic elements with dynamic structures and evolutionary histories.
- Their evolution involves insertion, homing endonuclease gene modification, and eventual loss.
- Despite functional conservation in RNA self-splicing, these introns exhibit remarkable structural plasticity.
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