Recombinant mitochondrial DNA molecules suggest a template switching ability for group-II-intron reverse transcriptase

Degenerative processes in the filamentous fungus Podospora anserina are strongly correlated with the instability of the mitochondrial genome. Among the sources of instability is the mobile group-II intron COX1-i1, also called intron α, which encodes a protein with a reverse transcriptase activity. In this paper we characterize, through PCR experiments, mitochondrial recombinant DNA molecules joining the 5′ end of intron α to the 3′ end of tRNA sequences including the CCA motif. The structure of these junctions led us to propose that they were most probably initiated by a RNA template switching of the reverse transcriptase encoded in COX1-i1. This activity might be involved in a number of mitochondrial rearrangements occurring in degenerative syndromes and in some long-lived mutants.