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Zea ribosomal repeat evolution and substitution patterns
1Division of Biological Sciences, University of Missouri, Columbia 65211, USA. buckler@biosci.mbp.missouri.edu
Molecular Biology and Evolution
|April 1, 1996
Summary
This study analyzed Zea and Tripsacum ribosomal DNA internal transcribed spacer (ITS) sequences. Selection and mutation processes like deamination shape ITS evolution, revealing constrained regions critical for gene function.
Area of Science:
- Molecular Evolution
- Genetics
- Bioinformatics
Background:
- The nuclear ribosomal internal transcribed spacer (ITS) is crucial for ribosomal RNA gene function.
- Understanding ITS evolution provides insights into genome evolution and regulatory mechanisms.
Purpose of the Study:
- To investigate concerted evolution, substitution rates, and structural constraints within the ITS of Zea and Tripsacum.
- To identify and characterize ITS pseudogenes and their evolutionary drivers.
Main Methods:
- Phylogenetic analysis of Zea and Tripsacum nuclear ribosomal internal transcribed spacer (ITS) sequences.
- Assessment of nucleotide composition, substitution rates, and secondary RNA structures.
- Identification of pseudogenes based on phylogenetic position and molecular characteristics.
Main Results:
- ITS pseudogenes were identified through distinct phylogenetic positions and altered nucleotide composition.
- Methylation-induced deamination significantly contributed to mutations, yet selection maintained high methylation site density.
- Substitution rates varied considerably among Zea taxa, with constrained regions found at the 5' ends of ITS1 and ITS2.
Conclusions:
- Selection plays a key role in shaping ITS polymorphisms and substitutions.
- Methylation-induced deamination is a potent mutation source, balanced by selective pressures.
- Specific regions within the ITS are under strong selective constraint, indicating functional importance.