Fate of a Larch Unedited tRNA Precursor Expressed in Potato Mitochondria

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.

Life without post-transcriptional addition of G−1: two alternatives for tRNAHis identity in Eukarya

“…These observations indicate a division of labor in A. castellanii, wherein two independent and coexisting mechanisms for tRNA His identity have evolved that are strictly compartmentalized. Inconsistencies in the occurrence of even the encoded G −1 on tRNA His have been previously reported in plant mitochondria and chloroplast (Marechal-Drouard et al 1996a,b;Placido et al 2005Placido et al , 2010.…”

Polyadenylation in RNA Degradation Processes in Plants

“…An alternative explanation is these transcripts are recognized as mis-processed RNAs and therefore targeted to rapid degradation. Similarly, PNPase probably degrades other type of misprocessed RNAs such as misfolded tRNA precursors (Placido et al 2005). However, specific quality-control mechanism that monitors for example mRNA editing appear to be absent in plant mitochondria (Holec et al 2008a) Another role of PNPase is the elimination of tRNA and rRNA maturation by-products (Holec et al 2006).…”

Large gene overlaps and tRNA processing in the compact mitochondrial genome of the crustaceanArmadillidium vulgare

“…vulgare total nucleic acid was first treated with DNASE RQ1 according to manufacturer's intructions (Promega). The DNase-treated RNA sample was then used as substrate for RT-PCR amplification using relevant pairs of primers, cloned into pGEM-T Easy (Promega), as described in 51 and sequenced.…”

“…51 Briefly, total RNA extracted from A. vulgare was incubated with 40U of T4 RNA ligase (New England Biolabs) in the supplied buffer supplemented with 2U of RNase inhibitor and in a total volume of 25 ml. Following circularization, all steps of RT-PCR were classically carried out using a relevant pair of primers.…”