Supercomplex of photosystem and antenna —organization and function—

From environmental input, To physiological output

I’m interested in a supermolecular organization of photosystem complexes. My lovely target organisms are cyanobacteria. They perform oxygen-evolving photosynthesis using two photosystems, photosystem I and photosystem II. The name of cyanobacteria comes from their “blue-green” color. But cyanobacteria are more colorful, not only the blue-green but also red, purple, pink and more. The color palette is thanks to their major antenna protein complex “phycobilisome”. Phycobilisome is composed of many colorful chromophore-binding proteins, phycobiliproteins, and their associated linker proteins. The typical phycobilisome consists of several peripheral rods radially projected from a core. A rod-core linker protein CpcG anchors the rod to the core.

Optimization of the photosynthesis is vital for photosynthetic organisms to survive a continually changing environment. Re-organization of light-harvesting antenna systems and photosystems is the primary way for that. Previously, I discovered a novel supercomplex of the photosystem I and a specific phycobilisome, CpcL-phycobilisome, from Anabaena sp. PCC 7120. CpcL-phycobilisome is a rod-type phycobilisome that lacks the core components. It is directly connected with the photosystem I specifically by a linker protein CpcL to form a Phycobilisome-CpcL-Photosystem I supercomplex. Both the typical phycobilisome and the CpcL-phycobilisome can transfer the energy to photosystem I. However, how the cells control the two different types of phycobilisome remains elusive. I aim to reveal the molecular mechanisms of how environmental input can affect the organization of the two distinct phycobilisomes. And also, I want to uncover what is the difference in the physiological roles of the two phycobilisomes as the photosystem I antenna.

Mai Watanabe
Post-doc researcher
JSPS Overseas Research fellow – Restart Research Abroad

Mai Watanabe is a post-doc of JSPS Overseas RESTART Research Fellowship in the lab of Prof. Annegret Wilde at Freiburg University. She is interested in How environmental signals regulate the organization of the photosystem and antenna complexes.