Plate Nº 67 · recorded November 14, 2026
Biology & EvolutionReported finding
'Planimal' Cells Keep Nearly Whole Algal Genome for 155 Generations
Tokyo researchers fused hamster cells with red algae and the hybrids kept 16.3 million DNA base pairs across 155 generations, with most foreign genes silenced.
By Elena Vasquez3 min read675 words
In brief
- Hybrid cells retained 16.3 million base pairs of algal DNA, including sequences from all 20 algal chromosomes, for 155 generations.
- Algal DNA persisted 95 generations without antibiotic selection.
- About 96% of transferred algal protein-coding genes showed no detectable expression.
- Cell fusion produced stable hybrids far more efficiently than engulfment of algae by hamster cells.
- Published in Nature Communications (2026), DOI 10.1038/s41467-026-78753-w.
Hybrid "planimal" cells built by University of Tokyo researchers retained roughly 16.3 million base pairs of algal DNA — sequences from all 20 algal chromosomes — and passed that foreign genetic material to daughter cells for 155 generations. The findings, published in Nature Communications, offer the first detailed picture of what happens when chromosome-scale DNA from one distant kingdom of life lands inside a mammalian cell.
The experiments test an evolutionary question. More than 1.5 billion years ago, an ancestral eukaryotic cell engulfed a cyanobacterium, a photosynthetic bacterium that eventually became the chloroplast — the sunlight-harvesting structure in today's algae and plants. Over evolutionary time, many genes from that captured bacterium moved into the host's nuclear genome, fusing two organisms into one integrated system.
Scientists understand horizontal gene transfer — DNA acquisition outside ordinary reproduction — reasonably well in bacteria, which take up free-floating DNA or swap genes through cell-to-cell tubes, spreading traits like antibiotic resistance. But genome-scale transfers between distantly related eukaryotes, organisms whose cells hold nuclei, are rarely documented directly.
How do you make a planimal cell?
Sachihiro Matsunaga, senior author and professor at the University of Tokyo's Laboratory of Integrated Biology, framed the team's goal plainly: "We wanted to understand whether entire chromosomes could cross the enormous evolutionary divide between algae and animals and whether animal cells could stably maintain and pass on such foreign genetic material to their daughter cells."
The team, led by University of Tokyo scientists, fused photosynthetic algal cells with hamster-derived mammalian cells, or let the mammalian cells engulf the algae outright. Fusion worked far better. It produced stable hybrid cells much more efficiently than engulfment did. Live-cell imaging and genome sequencing then tracked how the host cells handled the algal DNA across generations.
In one hamster-derived cell line, the retained algal nuclear DNA included intact chromosomes and material from all 20 algal chromosomes. Substantial portions persisted for 95 generations even without antibiotic selection, the standard lab technique for isolating genetically modified cells. That means the DNA didn't need active help to stay put.
"Plants and animals cannot reproduce with each other, so their chromosomes are never combined through mating," Matsunaga said. "Yet, we have succeeded in creating hybrid chromosomes containing genetic material from both an alga and a mammal."
Why didn't the foreign genes wreck the cell?
The answer appears to be epigenetic gatekeeping — changes in gene function that don't alter the DNA sequence itself. Most transferred algal genes were switched off. The foreign DNA picked up DNA methylation and repressive histone marks, chemical modifications associated with silencing genes.
The researchers tested the mechanism directly. When they repeated the experiment in hamster cells lacking DNMT3A, an enzyme that establishes DNA methylation, fewer stable hybrid colonies formed, and the surviving cells retained less algal DNA. The silencing machinery, in other words, helps mammalian cells tolerate huge amounts of foreign DNA while keeping imported genes quiet.
About 96% of transferred algal protein-coding genes showed no detectable activity. That silence is the study's main limitation — and its next opportunity.
Could animal cells ever photosynthesize?
Not yet. The study did not produce photosynthetic animal cells, and the researchers say that goal remains distant, requiring functional chloroplasts and substantial further engineering.
"Our next challenge is to selectively switch on the genes we need and make them work inside animal cells," Matsunaga said. "The red alga we use has a remarkably compact genome containing genes for metabolic functions that animal cells do not possess."
The long-term vision, he said: "Imagine animal cells that could sustain photosynthesis for long periods, producing oxygen while using carbon dioxide to make useful organic compounds."
For now, the result stands as proof that even a billion-plus-year evolutionary gulf between plants and animals can be crossed at the chromosome level — no reproduction required.
The paper is Ryota Aoki et al., "Epigenetic gatekeeping enables genome-scale horizontal gene transfer in eukaryotic cells," Nature Communications (2026), DOI: 10.1038/s41467-026-78753-w.
via phys.org/rss-feed/ (Source)
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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