Meiosis normally reshuffles hybrid genomes through recombination and halves chromosome number. A 2024 Nature Genetics study established ‘mitosis instead of meiosis’ (MiMe) in tomato so hybrids could produce unreduced clonal gametes and be combined into designed tetraploid genomes.
Three meiotic genes create clonal 2n gametes
Mutating tomato SlSPO11-1, SlREC8 and SlTAM replaced key meiotic processes and enabled three hybrid tomato genotypes to produce largely clonal unreduced gametes.
Two MiMe hybrids produced 4-Hap offspring
Crosses between distinct MiMe hybrids generated tetraploid plants containing the complete genetic repertoire of four inbred grandparents. Haplotype-specific SNP markers confirmed all four genome sets.
This is closer to combining predefined parental haplotypes without recombination than to freely “adding genes.”
The work establishes polyploid genome design as a proof of concept. Commercial yield benefits, stable seed multiplication, fertility and long-term genome stability still require further breeding-system development.
For related context, see How Are Japanese Soybeans Genomically Different? A 462-Accession Pangenome—and Two Author Corrections.
For related context, see SW14 Rebalances Soybean Seed Weight, Protein and Oil by Disrupting a LEC1-Containing NF-Y Complex.
For related context, see Indica OsNLP4 Raised Yield and Nitrogen-Use Efficiency in Japonica Rice Across Multi-Location Field Trials.
Reference
- Underwood CJ et al. Harnessing clonal gametes in hybrid crops to engineer polyploid genomes. Nature Genetics. 2024;56:1075–1079. https://doi.org/10.1038/s41588-024-01750-6
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