< NINS ASTROBIOLOGY CENTER >NINS ASTROBIOLOGY CENTER
The Astrobiology Center (ABC) in NISS was established in 2015 to promote interdisciplinary studies that
include astronomy, earth science, and biology by organizational adaptation between National Astronomical
Observatory of Japan (NAOJ) and National Institutefor Basic Biology (NIBB). In the 2021 fiscal year, ABC
stayed active to encourage interdisciplinary studies
and grow the research community as the hub institute of astrobiology despite social constraints under
the COVID-19 pandemic. ABC symposium was held
online on Jan 28th, 2022, inviting speakers from diverse
research fields including an observatory mission byJames Webb Space Telescope. Life in the Universe
Workshop was also held online on Feb 17th-18th,
2022 to present the latest results from ABC-subsidizedresearch.

LABORATORY OF BIOLOGICAL DIVERSITYTAKIZAWA GroupSpecially Appointed Associate Professor

TAKIZAWA, Kenji

The Takizawa group operating out of ABC is currently studying
the environmental responses of photosynthesis in order to predict
photosynthetic apparatus of so-called ‘Alien’ plants under
extreme conditions on the aforementioned ‘Another Earth’.

Light adaptation mechanisms of photosynthesis

We investigated the flexible molecular mechanisms of lightharvesting and following photosynthetic reactions in cooperation with the division of environmental photobiology. In
photosynthesis research, we are specialized in spectroscopic
analyses which can be applied to astrobiology studies.

Characterize hypothetical plants in exo-planets

Figure 1. ABC mascot characters: “Exoplanet Friends” (Credit:
Hayanon Science Manga Studio)

Three project offices in ABC are working together
to find a habitable exo-planet and a sign of life on
said planet. Exo-Planet Search Project Office andAstrobiology Instrument Project Office which arelocated in the Mitaka campus of NAOJ are preparing
direct-imaging surveys of “Another Earth” by next-generation, 30m-scale telescopes. To support future observation projects, three groups from NIBB in Okazaki, theTakizawa, Johzuka, and Fujita groups, are participatingin the Exo-Life Search Project Office to investigate
life on Earth utilizing three different approaches: 1)
assessing the biosignature of various photosyntheticorganisms to predict biosignatures of hypothetical lifeon exoplanets, 2) evaluating the effects of cosmic radiation on living cells, and 3) elucidating mathematicalprinciples in the formation of self-organizing structuresin organisms.

One of the most plausible biosignatures detected by theexo-planet observations is a specific reflection pattern on
the land surface named ‘vegetation red edge’ or VRE. VRE
arises from strong absorption of red light by photosynthetic
pigments and high reflectance of near-infrared radiation(NIR) by the developed leaf tissue structure. The wavelength
position and amplitude of VRE could be different on anotherplanet. We studied the light reflection spectrum of various
plants and predicted that substantially large VRE could beobserved even on the ocean planets if floating plants cover
the water surface (Figure 2). We also predicted the possibilityof red-sift in VRE on the planets exposed to NIR rather thanvisible light. We have revealed that several metal-containing
pigments can be functional in reaction centers under NIR
radiation conditions via quantum chemical calculations.

Figure 2. Remote sensing of light reflectance of floating leaf of waterlily.
Light reflectance in visible light (RGB) and NIR were obtained by thedrone-based multiband sensor.

Publication List:〔Original papers〕

Y., and Takizawa, K. (2021). A quantum chemical study on the• Komatsu,
effects of varying the central metal in extended photosynthetic pigments.

•Phys. Chem. Chem. Phys. 23, 14404–14414. DOI: 10.1039/d1cp00760b
Pan, X., Tokutsu, R., Li, A., Takizawa, K., Song, C., Murata, K.,
Yamasaki, T., Liu, Z., Minagawa, J., and Li, M. (2021). Structural basisof LhcbM5-mediated state transitions in green algae. Nat. Plants 7,1119+. DOI: 10.1038/s41477-021-00960-879