Organellar transcriptome sequencing reveals mitochondrial localization of nuclear encoded transcripts.

Mitochondria are organelles involved in a variety of biological functions in the cell, apart from their principal role in generation of ATP, the cellular currency of energy. The mitochondria, in spite of being compact organelles, are capable of performing complex biological functions largely because of the ability to exchange proteins, RNA, chemical metabolites and other biomolecules between cellular compartments. A close network of biomolecular interactions are known to modulate the crosstalk between the mitochondria and the nuclear genome. Apart from the small repertoire of genes encoded by the mitochondrial genome, it is now known that the functionality of the organelle is highly reliant on a number of proteins encoded by the nuclear genome, which localize to the mitochondria. With exceptions to a few anecdotal examples, the transcripts that have the potential to localize to the mitochondria have been poorly studied. We used a deep sequencing approach to identify transcripts encoded by the nuclear genome which localize to the mitoplast in a zebrafish model. We prioritized 292 candidate transcripts of nuclear origin that are potentially localized to the mitochondrial matrix. We experimentally demonstrated that the transcript encoding the nuclear encoded ribosomal protein 11 (Rpl11) localizes to the mitochondria. This study represents a comprehensive analysis of the mitochondrial localization of nuclear encoded transcripts. Our analysis has provided insights into a new layer of biomolecular pathways modulating mitochondrial-nuclear cross-talk. This provides a starting point towards understanding the role of nuclear encoded transcripts that localize to mitochondria and their influence on mitochondrial function.