We are exploring how genome editing can unlock new ways to design life at the cellular level. One of our most fascinating projects has been engineering Euglena gracilis to produce seeds in a variety of striking colors. Among them, the pink-hued variants have become a personal favorite—tiny living canvases that showcase both scientific progress and the beauty of biology.

This work builds on our recent research into carotenoids, a class of natural pigments that play essential roles in photosynthesis, protection against light stress, and cellular signaling. Earlier this year, we published a paper in Plant Physiology titled:

“Zeaxanthin is required for eyespot formation and phototaxis in Euglena gracilis”
Shun Tamaki, Kazunari Ozasa, Toshihisa Nomura, Marumi Ishikawa, Koji Yamada, Kengo Suzuki, Keiichi Mochida
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In that study, we used CRISPR/Cas9 genome editing to systematically knock out carotenoid biosynthetic genes in Euglena. We discovered that the carotenoid zeaxanthin is essential for the formation of the eyespot apparatus—a tiny, pigment-rich organelle that enables Euglena to sense light and move toward or away from it (a behavior known as phototaxis). Without zeaxanthin, cells failed to form stable eyespots and lost their ability to navigate light environments.

These findings highlight a fascinating evolutionary divergence:

• In green algae (chlorophytes), β-carotene is the key pigment for eyespot function.
• In Euglena gracilis, however, xanthophylls such as zeaxanthin are indispensable.

By editing carotenoid pathways, we not only uncovered the genetic basis of this light-sensing mechanism but also learned how to “repaint” Euglena itself—producing variants that display unique and vivid coloration.

Our ongoing experiments show that these genome-edited Euglena can generate seeds and microcolonies in multiple shades, opening up exciting directions in both fundamental biology and potential applications in bio-design, biomaterials, and education.

Funding

This work was supported by the Japan Science and Technology Agency (JST)-OPERA Program (No. JPMJOP1832) and (JST/JICA)-SATREPS Program (No. JPMJSA2204).