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Title: Group I introns are inherited through common ancestry in the nuclear-encoded rRNA of Zygnematales (Charophyceae). Author: Bhattacharya D, Surek B, Rüsing M, Damberger S, Melkonian M. Journal: Proc Natl Acad Sci U S A; 1994 Oct 11; 91(21):9916-20. PubMed ID: 7937917. Abstract: Group I introns are found in organellar genomes, in the genomes of eubacteria and phages, and in nuclear-encoded rRNAs. The origin and distribution of nuclear-encoded rRNA group I introns are not understood. To elucidate their evolutionary relationships, we analyzed diverse nuclear-encoded small-subunit rRNA group I introns including nine sequences from the green-algal order Zygnematales (Charophyceae). Phylogenetic analyses of group I introns and rRNA coding regions suggest that lateral transfers have occurred in the evolutionary history of group I introns and that, after transfer, some of these elements may form stable components of the host-cell nuclear genomes. The Zygnematales introns, which share a common insertion site (position 1506 relative to the Escherichia coli small-subunit rRNA), form one subfamily of group I introns that has, after its origin, been inherited through common ancestry. Since the first Zygnematales appear in the middle Devonian within the fossil record, the "1506" group I intron presumably has been a stable component of the Zygnematales small-subunit rRNA coding region for 350-400 million years.[Abstract] [Full Text] [Related] [New Search]