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Parallel functional reduction in the mitochondria of apicomplexan parasites
Varsha Mathur1, Kevin C Wakeman2, Patrick J Keeling1
1Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Current Biology : CB
|May 11, 2021
Summary
Gregarines, early parasites, show significantly reduced mitochondria, lacking key respiratory components. This parallel evolution highlights diverse mitochondrial adaptations in apicomplexans.
Area of Science:
- Evolutionary biology
- Parasitology
- Cell biology
Background:
- Gregarines are early-diverging apicomplexan parasites, offering insights into the transition from free-living algae to animal parasites.
- Understanding their biology is crucial for deciphering apicomplexan origins and evolution.
Purpose of the Study:
- To characterize the mitochondrial metabolic repertoire across apicomplexan lineages, focusing on understudied gregarines.
- To investigate the evolutionary trajectory of mitochondria in gregarines and its implications for apicomplexan evolution.
Main Methods:
- Single-cell transcriptomics was employed to analyze mitochondrial proteins in gregarine trophozoites.
- Phylogenomic analyses were conducted to trace the evolution of mitochondrial components and genome loss.
- Comparative analysis with well-studied apicomplexans like Toxoplasma and Plasmodium was performed.
Main Results:
- Gregarine trophozoites exhibit significantly reduced energy metabolism, often lacking respiratory complexes III and IV, and sometimes the entire electron transport chains (ETCs) and tricarboxylic acid (TCA) cycle.
- Mitochondrial genome loss occurred repeatedly, with gene relocation to the nucleus observed in one species.
- Despite functional reduction, gregarines maintain distinctive mitochondria with tubular cristae, even in cases lacking genes for cristae formation.
Conclusions:
- Parallel, severe reduction of mitochondria in gregarines expands the known diversity of mitochondrial-related organelles (MROs).
- These findings emphasize the significant role of parallel evolutionary transitions in shaping apicomplexan mitochondrial diversity.
- Gregarines present a unique model for studying extreme mitochondrial reduction and adaptation within parasites.
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