Evolutionary transfer of ORF-containing group I introns between different subcellular compartments (chloroplast and mitochondrion).

摘要: We describe here a case of homologous introns containing open reading frames (ORFs) that are inserted at the same site in large subunit (LSU) rRNA gene different organelles distantly related organisms. show chloroplast LSU green alga Chlamydomonas pallidostigmatica contains group I intron (CpLSU.2) encoding site-specific endonuclease (I-CpaI). This is identical (corresponding to position 1931-1932 Escherichia coli 23S sequence) as (AcLSU.m1) mitochondrial amoeboid protozoon Acanthamoeba castellanii. The CpLSU.2 displays remarkable degree nucleotide similarity both primary sequence and secondary structure AcLSU.m1 intron; moreover, an ORF location within its shares with it strikingly high level amino acid (65%; 42% identity). A comprehensive survey distribution 1931 reveals rather restricted occurrence polyphyletic genus Chlamydomonas, no evidence this among number non-Chlamydomonad algae surveyed, nor land plants. parallel homologues previously described similar intron/ORF pair (C. reinhardtii CrLSU/A. castellanii AcLSU.m3) also shows (site 2593) chloroplasts, although somewhat broader than observed 1931, site-2593 appearing several algal branches outside lineage. available data, while not definitive, most consistent relatively recent horizontal transfer site-1931 (and their contained ORFs) between Chlamydomonas-type organism mitochondrion Acanthamoeba-like organism, probably direction mitochondrion. data suggest could have been acquired single event.