Sequence diversity of the 1.3 kb retron (retron-Ec107) among three distinct phylogenetic groups of Escherichia coli.
In the preceding paper, we showed that a new 1.3 kb retron (retron-Ec107) in Escherichia coli is responsible for the biosynthesis of a branched-RNA-linked multicopy single-stranded DNA (msDNA-Ec107). Here, we show that this retron occurs in strains from different branches, A, B1, and D of a well-defined phylogenetic tree of a collection of wild E. coli. Sequence comparisons of the retrons from these three branches were carried out. Sequence homology was well conserved among the strains within the same branch and the retron sequence from branch A was exactly the same with that from branch D, while there were 18 base substitutions between the retrons from branch B1 and A or D, resulting in seven amino acid substitutions in reverse transcriptase. No substitutions were found in the msDNA- and msdRNA-coding regions, and there was no difference in the ability of msDNA production between them. These results suggest that the retron has probably been integrated into at least one of the three branches at an early stage of evolution and subsequently transferred to the other two branches, and also that the msDNA-producing system has been conserved during evolution with some mutations in the retron.
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854.
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D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics*; D004926:Escherichia coli / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D012329:RNA, Bacterial; C058681:msDNA; D012194:RNA-Directed DNA Polymerase