Alternative splicing of the Euglena gracilis chloroplast roaA transcript

A novel gene, roaA (ribosomal operon-associated gene), encoding a potential RNA-binding protein has been identified in the rpl23 ribosomal protein operon of the Euglena gracilis chloroplast genome. The roaA gene is interrupted by one group III and three group II introns. Introns 1 and 2 of roaA can be interpreted as a twintron, formed from the insertion of a group II intron into the 5'splice site of a group III intron. Alternative splicing of the group III intron results in two distinct transcripts encoding proteins of 516 and 514 amino acids. Group III introns may play a role in the generation of alternatively spliced transcripts.