The SSU rDNA coding region of a filose amoeba contains a group I intron lacking the universally conserved G at the 3'-terminus.
We sequenced small subunit ribosomal DNA (rDNA) PCR-fragments of sizes 2.3 kb and 2.9 kb isolated from a culture of the red alga, Porphyra spiralis var. spiralis. Phylogenetic analysis of the 2.3-kb fragment showed that it encoded the sequence of a contaminant filose amoeba. The Nuclearia-like amoeba (named strain N-Por) was identified with scanning electron microscopy. Its rDNA sequence was positioned with strong bootstrap support within a diverse protist assemblage that includes filose amoebae, chlorarachniophytes, cercomonads, and Plasmodiophora brassicae. The rDNA of N-Por contained a group I intron at the conserved 943 position that remarkably, had a U at the 3'-terminus rather than the universally conserved G.
Bhattacharya
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University of Iowa, Department of Biological Sciences, Iowa City 52242-1324, USA. dbhattac@blue.weeg.uiowa.edu
Oliveira
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D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics*; D056890:Eukaryota / Q000145:classification / Q000235:genetics*; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D000461:Rhodophyta / Q000235:genetics
D016054:DNA, Protozoan; D004275:DNA, Ribosomal