Unorthodox information processing systems in mitochondria

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***Unconventional information processing system in Diplonema mitochondria: transcripts from jigsaw-puzzle genes mended by 'joinosomes'******Mitochondria are an integral part of the eukaryotic cell, supplying it with energy and molecular building blocks such as amino acids and nucleotides. This organelle is special because it possesses its own genome and own machineries for DNA replication, transcription, and translation. While mitochondria across extant eukaryotic species originated from the same bacterial ancestor, they have substantially changed and diversified over time, the reason for referring to mitochondria as Nature's evolutionary playground.******Our overarching research PROGRAM seeks to elucidate how mitochondria are functioning: from storage of genetic information to transcriptional gene regulation, RNA processing, and protein synthesis. Much remains to be discovered in particular in microbial eukaryotes that are largely unexplored. The few non-model systems investigated so far have provided just a glance at the extraordinary diversity of mitochondrial gene expression and the underlying molecular machineries and mechanisms.******Our five-year research PROPOSAL aims at investigating most eccentric mitochondria that we discovered in a group of marine protozoans, the diplonemids. Their genes are systematically fragmented, with gene pieces transcribed separately and only then joined into mature messenger RNAs or ribosomal RNAs. This kind of gene structure and transcript maturation (definitely distinct from conventional intron splicing) has never been reported before. The question is how exactly the matchmaking and joining of RNA pieces is achieved in the type species Diplonema papillatum. Our hypotheses are: matchmaking is assured by proteins; pieces are stitched together by an RNA ligase of the just recently discovered RtcB type; and these components are part of a postulated mitochondrial joinosome' complex.******The Diplonema nuclear genome contains three distinct RtcB genes (Dp-RtcB1, 2, 3). To unravel their function, the proposed research has the following AIMS and OBJECTIVES:*** 1. Establish the biological roles of Dp-RtcBs by determining the proteins' interaction partners and the genes' evolutionary origins.*** 2. Identify the postulated mitochondrial joinosomes by investigating catalytic activity and substrate preferences.***These aims will be addressed by an APPROACH combining classical biochemistry, genomics, proteomics, and bioinformatics.******EXPECTED OUTCOME: insight into (i) the makeup of the postulated joinosomes, (ii) the molecular mechanism of this unique RNA joining process, and (iii) the evolutionary path leading to such a seemingly improbable process. Projects like this will strengthen Canada's contributions to fundamental research --the foundation of all innovation. Further, the gained knowledge will likely expand our experimental tool box for molecular engineering, with promising applications from environment to human health.**