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Analysis of dinucleotide frequency and codon usage in the phylum Apicomplexa
J Ellis1, H Griffin, D Morrison
1Department of Microbiology, University of Technology, Sydney, New South Wales, Australia.
Gene
|April 30, 1993
Summary
Codon usage in parasitic protozoa is non-random and species-specific, influenced by taxonomy. Dinucleotide frequencies, particularly TA and CG, are low, with coding pressure explaining variations in some species.
Area of Science:
- Genomics
- Parasitology
- Molecular Biology
Background:
- Apicomplexa parasites exhibit species-specific codon usage (cu) and dinucleotide frequencies (DiF).
- Understanding these patterns is crucial for deciphering genomic constraints and evolutionary pressures in parasitic protozoa.
Purpose of the Study:
- To analyze dinucleotide frequency and codon usage in four Apicomplexa species: Babesia bovis, Theileria parva, Toxoplasma gondii, and Eimeria tenella.
- To investigate the relationship between codon usage, dinucleotide frequencies, and taxonomic position within Apicomplexa.
- To determine the role of coding pressure in shaping these genomic features.
Main Methods:
- Comparative analysis of gene sequences from B. bovis, T. parva, T. gondii, and E. tenella.
- Assessment of dinucleotide frequencies (DiF) and codon usage (cu) patterns.
- Comparison of DiF ratios in coding regions, rRNA-encoding genes, and introns.
Main Results:
- Codon usage was non-random, species-specific, and similar within the same subclass, supporting the 'genome hypothesis'.
- Several low-usage (lu) codons were identified, with their usage correlating with taxonomic position.
- A low frequency of TA and CG dinucleotides was observed in all studied organisms' gene coding regions.
- In piroplasms (B. bovis, Th. parva), low dinucleotide frequency was attributed solely to coding pressure.
- In coccidia (T. gondii, E. tenella), coding pressure alone did not fully explain dinucleotide frequency variations.
Conclusions:
- Codon usage and dinucleotide frequencies in Apicomplexa are shaped by both evolutionary and functional constraints.
- Taxonomic relatedness influences codon usage patterns, suggesting conserved mechanisms within subclasses.
- The interplay between coding pressure and other factors in dinucleotide frequency variation warrants further investigation, particularly in coccidia.