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Phylogenetic relationships among group II intron ORFs.
1Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada. zimmerly@ucalgary.ca
Nucleic Acids Research
|February 27, 2001
Summary
Mobile group II introns, potential ancestors of spliceosomal introns, show a bacterial origin. Phylogenetic analysis reveals two lineages and extensive horizontal gene transfer, suggesting early domain loss and expansion.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Genomics
Background:
- Group II introns are hypothesized ancestors of spliceosomal introns, but their evolutionary history remains unclear.
- Understanding the evolution of mobile group II introns is crucial for deciphering intron and genome evolution.
Purpose of the Study:
- To investigate the evolutionary history and origin of mobile group II introns.
- To analyze the phylogenetic relationships of group II intron reverse transcriptases (RTs).
Main Methods:
- Compiled 71 open reading frames (ORFs) related to group II intron RTs.
- Performed phylogenetic analysis on derived amino acid sequences.
- Rooted the phylogenetic tree with RTs from non-long terminal repeat retroelements.
Main Results:
- Inferred phylogeny revealed two major clusters: mitochondrial and chloroplast-like lineages.
- Bacterial ORFs were found at the base of both lineages, indicating potential horizontal transfer.
- Evidence of multiple losses of the Zn domain and YADD motif was observed.
- Domain structures suggest an initial concise ORF that expanded in the mitochondrial lineage.
Conclusions:
- The data support a bacterial origin for mobile group II introns.
- High rates of horizontal transfer, including between organelles and bacteria, were inferred.
- Evolutionary changes involved domain loss and ORF expansion.