The mtDNA rps3 locus has been invaded by a group I intron in some species of Grosmannia

The mitochondrial rps3 gene in some filamentous ascomycetes fungi is encoded within an rnl group I intron. In Grosmannia piceiperda the N-terminal segment of the intron-encoded rps3 gene has been invaded by an IC2-type group I intron. This intron disrupts the recipient rps3 and fragments this gene into two open reading frames (ORFs). The IC2 group I intron encodes a putative double-motif LAGLIDADG ORF, which is fused in-frame to the upstream rps3 exon sequence. The presence of the LAGLIDADG amino acid motif is indicative of an enzyme that has endonuclease and/or maturase activity and thus the intron encoded protein could be involved in promoting splicing and mobility. Reverse transcriptase polymerase chain reaction (RT-PCR) confirmed that this intron is spliced in vivo and as a result this could allow for the expression of a functional ribosomal Rps3 protein.