1995 Fiscal Year Final Research Report Summary
Evolution and horizontal transmission of group I self-splicing introns
| Project/Area Number |
06454037
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物・生体工学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
YAMADA Takashi Hiroshima University, Faculty of Engineering : Professor, 工学部, 教授 (40230461)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUCHI Yo Toyohashi University of Technology, Faculty of Engineering : Professor, 工学部, 教授 (40273320)
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| Project Period (FY) |
1994 – 1995
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| Keywords | ribozyme / group I intron / self-splicing / Chlorella / Chlorella virus |
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| Research Abstract |
Two group I self-splicing introns were found and characterized in the rRNA genes of the unicellular green alga Chlorella ellipsoidea. The primary sequence and secondary structure of of these introns are very similar to those of group IB introns so far found in various organisms belonging to different phylogenetic kingdoms ; for example, the homology between the Chlorella small subunit rRNA intron [Ce (SSU) ] and that of the pathogenic yeast Pneumocystis carinii [Pc (SSU) ] is higher than 80% and the Chlorella large subunit rRNA intron [Ce (LSU) ] showed a homology higher than 80% to the Tetrahymena intron [Tt (LSU) ]. When the 82 "core" nucleotides of the intron were compared among 19 different organisms including 11 green algae, 1 red alga, 2 yeasts, and 1 protist, it was found that they are highly conserved independent of the phylogenetic relationship of the host organisms. These results strongly suggest that the origins of these introns are the same and they have spread and evolved very recently. Therefore, the mechanism of "horizontal intron transmission" is interesting to know. In this study, we discovered a special kind of viruses that can be considered as a possible candidate for the mediator of intron spreading at least among algae, yeasts, and protists. The viruses that infect unicellular green algal Chlorella cells contained group I self-splicing introns. Molecular comparative analysis of the intron structure revealed a remarkably close relatedness of these viral introns with above mentioned group IB introns. These eukaryotic viral introns offer an opportunity to understand how group I introns reach organisms of different phylogenetic kingdoms.
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