Related Experiment Videos
An ancient group I intron shared by eubacteria and chloroplasts.
M G Kuhsel1, R Strickland, J D Palmer
1Department of Biology, Indiana University, Bloomington 47405.
Science (New York, N.Y.)
|December 14, 1990
Summary
Introns, genetic elements found in most organisms, were present in cyanobacteria and chloroplasts over a billion years ago. This suggests these genetic elements were inherited from a common ancestor, not recently acquired.
Area of Science:
- Molecular Biology
- Genetics
- Evolutionary Biology
Background:
- Introns are typically absent in eubacteria but present in organelles of eubacterial origin (chloroplasts, mitochondria).
- This raises questions about intron origin: recent organelle acquisition or loss from bacterial ancestors.
- The leucine transfer RNA with UAA anticodon [tRNALeu (UAA)] gene is a target for studying intron evolution.
Purpose of the Study:
- To investigate the evolutionary history of introns in cyanobacteria and chloroplasts.
- To determine if the intron in tRNALeu (UAA) predates the divergence of cyanobacteria and chloroplasts.
Main Methods:
- Comparative sequence analysis of the tRNALeu (UAA) gene and its intron across diverse cyanobacteria and chloroplasts.
- Phylogenetic analysis to infer the intron's evolutionary history.
Main Results:
- A conserved group I intron was identified in the tRNALeu (UAA) gene of five cyanobacteria species and various chloroplast groups.
- The intron's position, primary sequence, and secondary structure are highly conserved.
- Homology indicates the intron was present in the common ancestor of cyanobacteria and chloroplasts.
Conclusions:
- The intron in tRNALeu (UAA) has been maintained for at least one billion years.
- This finding supports the hypothesis that introns were present in early life forms and have been lost in some lineages, rather than being recently acquired by organelles.