Mitochondrial Genome Dynamics in Plants

Plant mitochondrial genomes are among the most structurally and functionally dynamic of all eukaryotic organelles. They vary widely in size, gene content and physical conformation, often existing as a complex assortment of circular, linear and branched molecules rather than a single master circle. Large repeats drive high rates of recombination, generating multiple genome isoforms that can shift stoichiometrically in response to developmental cues or environmental stress. Despite remarkably low nucleotide substitution rates, plant mitogenomes undergo frequent rearrangements and occasional horizontal gene transfers, and many mitochondrial genes have been relocated to the nuclear genome. Heteroplasmy—the coexistence of distinct mitochondrial DNA variants within the same cell—further modulates organelle function. Recent breakthroughs in targeted genome editing and high-fidelity sequencing have begun to reveal the precise roles of individual mitochondrial genes in respiration, fertility and stress tolerance. These insights not only advance our understanding of organelle evolution and biogenesis but also open new avenues for crop improvement through synthetic cytoplasmic male sterility, enhanced hybrid breeding and resilience to changing climates. A thorough grasp of mitochondrial genome dynamics is therefore foundational for both basic plant biology and the sustainable intensification of agriculture.

Research from Nature Portfolio

Recent studies have uncovered extreme cases of mitochondrial genome fragmentation and gene reduction in photosynthetic eukaryotes. Work on multipartite minicircular chromosomes has revealed how individual cassette-bounded segments can recombine to form hetero-concatemers, offering a model for transitions between typical mitogenomes and highly reduced architectures. In parallel, precision genome editing using transcription activator-like effector nucleases targeted to mitochondria has enabled the clean deletion of a complex I subunit gene, nad9. Functional analyses of the resulting knockout lines demonstrated impaired respiratory complex assembly, male sterility and developmental defects, which could be rescued by nuclear expression of the deleted gene. This approach establishes reverse genetics in plant mitochondria and provides a platform for constructing synthetic cytoplasmic male sterility systems for hybrid seed production.

Mitochondrial Genome Dynamics in Plants publication trend

The graph below shows the total number of articles in mitochondrial genome dynamics in plants across all publications each year (not limited to Nature Index journals).

Technical terms

Heteroplasmy: The presence of more than one mitochondrial DNA variant within a single cell or organism.

Recombination: Exchange of DNA segments between repeats within the mitochondrial genome, generating alternative genome arrangements.

Copy number: The number of mitochondrial genome copies per cell, which can influence overall gene expression and organelle function.

Isoform: A distinct conformational variant of the mitochondrial genome resulting from recombination between repeats.

TALEN (Transcription Activator-Like Effector Nuclease): A programmable endonuclease used to introduce targeted double-strand breaks and deletions in mitochondrial DNA.

Cytoplasmic male sterility: A maternally inherited trait caused by mitochondrial gene mutations that prevent viable pollen formation, exploited in hybrid breeding.

References

1. The alternative reality of plant mitochondrial DNA: One ring does not rule them all. PLOS Genetics (2019).
2. Repeats of Unusual Size in Plant Mitochondrial Genomes: Identification, Incidence and Evolution. G3: Genes, Genomes, Genetics (2019).
3. The “fossilized” mitochondrial genome of Liriodendron tulipifera: ancestral gene content and order, ancestral editing sites, and extraordinarily low mutation rate. BMC Biology (2013).
4. Origin of minicircular mitochondrial genomes in red algae. Nature Communications (2023).
5. Targeted knockout of a conserved plant mitochondrial gene by genome editing. Nature Plants (2023).
6. Stochastic organelle genome segregation through Arabidopsis development and reproduction. New Phytologist (2023).
7. PMAT: an efficient plant mitogenome assembly toolkit using low-coverage HiFi sequencing data. Horticulture Research (2024).
8. Mitochondrial gene defects in Arabidopsis can broadly affect mitochondrial gene expression through copy number. Plant Physiology (2023).