Abstract
In higher plant mitochondria, post-transcriptional C to U conversion known as editing mostly affects mRNAs. However, three tRNAs were also shown to be edited. Among them, three editing sites were identified in larch mitochondrial tRNA(His). We have previously shown that only the edited version can undergo maturation in vitro. In this paper, we introduced via direct DNA uptake the edited or unedited version of larch mitochondrial trnH into isolated potato mitochondria and expressed them under the control of potato mitochondrial 18 S rRNA promoter. As expected, the edited form of larch mitochondrial tRNA(His) precursor was processed in the isolated organelles. By contrast, no mature tRNA(His) was detected when using the unedited version of trnH. However, precursor molecules could be characterized by reverse transcription-PCR. These data demonstrate that the potato mitochondrial editing machinery is not able to recognize these "foreign" editing sites and confirm that these unedited tRNA precursor molecules are not correctly processed in organello. As a consequence, the fate of these RNA precursor molecules is likely to be degradation. Indeed, we detected by PCR two 3'-end truncated precursor RNAs. Interestingly, both RNA species exhibit poly(A) tails, a hallmark of degradation in plant mitochondria. Taken together, these data suggest that, in plant mitochondria, a defective unedited RNA precursor that cannot be processed to give a mature stable tRNA, is degraded through a polyadenylation-dependent pathway.
Highlights
(CNRS, France) and by Dipartimento di Biochimica e Biologia Molecolare (Bari University, Italy)
We introduced via direct DNA uptake the edited or unedited version of larch mitochondrial trnH into isolated potato mitochondria and expressed them under the control of potato mitochondrial 18 S rRNA promoter
Our results indicated that larch mitochondrial trnH incorporated into potato mitochondria via direct DNA uptake was expressed under the control of a heterologous potato mitochondrial 18 S rRNA promoter
Summary
(CNRS, France) and by Dipartimento di Biochimica e Biologia Molecolare (Bari University, Italy). DNA repair mechanisms, tmRNA-directed proteolysis of unfinished protein, or nonsense-mediated mRNA decay represent good examples of such mechanisms Despite their importance, RNA quality control of stable RNAs is still largely unknown with only few and recent data available. Expression and Maturation of a Foreign tRNA Gene in Potato Mitochondria tRNAHis precursor transcripts, expressed in organello, cannot be edited and converted in mature and stable tRNAs. Rather, two 3Ј-end truncated precursor RNA species exhibiting poly(A) tails, a hallmark of degradation in plant mitochondria, were detected. Two 3Ј-end truncated precursor RNA species exhibiting poly(A) tails, a hallmark of degradation in plant mitochondria, were detected These results suggest that, in plant mitochondria, a defective unedited RNA precursor that cannot be processed to give a mature stable tRNA, is transiently polyadenylated and subsequently degraded
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