A self-splicing group II intron in the mitochondrial large subunit rRNA (LSUrRNA) gene of the eukaryotic alga Scenedesmus obliquus.

The DNA sequence has been determined of the 3' terminus from the mitochondrial large subunit ribosomal RNA (LSUrRNA) gene of the eukaryotic green alga Scenedesmus obliquus (strain KS3/2). The gene contains two intervening sequences with characteristic sequence motifs of group II and group I introns respectively. The exon/intron boundaries of the introns have been revealed by sequence determination of the mature rRNA. During RNA processing of the precursor RNA, several abundant RNA molecules are stably maintained in addition to the mature rRNA in vivo. In vitro transcripts of the LSUrRNA gene containing the group II intron (608 bp) display a strong 'self-splicing' activity under high salt conditions. The 608 bp intron is the first group II intron reported to be integrated into a LSUrRNA gene and represents the smallest self-splicing group II intron from eukaryotic organelles so far described.