Some animals like corals live symbiotically with photosynthetic organisms, absorbing energy in exchange for a place to photosynthesize, but don’t contain chloroplasts themselves. Others exhibit kleptoplasty, in which organisms extract chloroplasts from their food, famously observed in some sea slugs. However, they have to be regularly replenished, and it has never been shown that chloroplasts could be integrated into most species, including any mammals.

In 2024, the University of Tokyo injected chloroplasts, the organelle responsible for photosynthesis in plants and microbes, into hamster cells. Though they were assumed to be incompatible, the chloroplasts worked in tandem with the hamster cells for days, with detected electron transport associated with photosynthesis.

The chloroplasts were taken from red algae cells and inserted in hamster cell cultures, and during their activity, the altered cells grew faster, suggesting that the energy derived from photosynthesis was used for cell development. This is substantial both for the observed elevation in growth rate, but also the fuel provided in a carbon-negative manner. With further development, this innovation could mean huge things for cultured animal products, especially tissues, which require oxygen that could be supplied from the chloroplasts through photosynthesis. While tissue cultures can be suffocated by several layers of cells, this method delivers oxygen to animal cells, which has huge implications for cultured meat.

However, there is plenty of room for further research. The chloroplasts were manually inserted instead of naturally produced, and commercial production might require a more automated approach, such as gene editing for chloroplast production. The systems required to produce an entirely new organelle are complex, so a GM approach requires a great deal of research. Additionally, by day two of co-cultivation, researchers reported the thylakoid membrane of the chloroplasts seeming to collapse, completely disabled by day four. However, they suggested that genetic modification could support the chloroplasts for longer periods, which would enable practical applications in cultures. While the applications of biotechnology-induced photosynthesis are far from implementation, they could revolutionize animal systems and reveal fascinating new paths in biotechnology.

In AP bio my senior year, I was extremely excited to learn about the slug that steals chloroplasts from its food, though it turns out there are more than one. The “photosyntheslugs” are an incredible feat of nature, and it’s surprising that they aren’t known by more people. I once tried talking about them to my mom, but she didn’t know what photosynthesis was, so I ended up spending more time explaining how plants work than about kleptoplasty.

This research is incredibly exciting because of the doors it opens in cell culture technology and sustainability, as photosynthesis provides energy while sequestering carbon, so it’s a real win-win. Plus it’s just super cool!

I mentioned cultured meat in this article, which I’m excited to continue discussing in a future article! Would you prefer that article next week or Ebola Part Two? Let me know in the comments and stay tuned to learn with me!

https://www.sciencedaily.com/releases/2024/10/241030150215.htm

https://www.jstage.jst.go.jp/article/pjab/100/9/100_pjab.100.035/_html/-char/en