NIBB Departments

Division of Environmental Photobiology

Staff

Research Summary

Plants and algae have versatile abilities to acclimate themselves to changing environments. Our research focuses on these acclimation processes, specifically investigating how these organisms efficiently and safely harness sunlight for photosynthesis under fluctuating light conditions. Using a model green alga, we are studying the molecular mechanisms underlying the photoacclimation of photosynthetic machinery. Furthermore, we apply the insights obtained in the studies of this model green alga to a variety of photosynthetic organisms, including marine phytoplankton and vascular plants, to explore how these environmentally important organisms thrive within their respective ecological niches.

Research Projects

• Photoacclimation of the marine phytoplankton Ostreococcus tauri
• Molecular mechanisms underlying the induction of non-photochemical quenching in Chlamydomonas reinhardtii
• Multimers of photosynthetic supercomplexes that regulate light-harvesting and photoprotection
• Characterization of the far-red light absorbing light-harvesting complex in the antarctic green alga
• Light-harvesting systems in the psychrophilic green alga

I. Plant and Algal PSII–LHCII Supercomplexes: Structure, Evolution and Energy Transfer.

Photosynthesis is the process conducted by plants and algae to capture photons and store their energy in chemical forms. The light-harvesting, excitation transfer, charge separation and electron transfer in photosystem II (PSII) are the critical initial reactions of photosynthesis and thereby largely determine its overall efficiency. Knowledge about the architectures and assemblies of plant and green algal PSII–light harvesting complex II (LHCII) supercomplexes are rapidly accumulating (Figure 1). We made pair-wise comparative analyses between the supercomplexes from plants and green algae to gain insights about the evolution of the PSII–LHCII supercomplexes involving the peripheral small PSII subunits that might have been acquired during the evolution (Figure 2) nd about the energy transfer pathways that define their light-harvesting and photoprotective properties (Figure 3) (Sheng et al., Plant Cell Physiol., 62:1108-1120).

Figure 1. The overall architecture of PSII–LHCII supercomplexes from C. reinhardtii and vascular plants (C₂S₂ from Spinacia oleracea, C₂S₂M₂ from pea). Sheng et al. (2021) Plant Cell Physiol., 62:1108-1120.

Figure 2. Superposition of green algal and plant PSII–LHCII supercomplexes and evolutionary insights from pea C₂S₂M₂ and C. reinhardtii C₂S₂M₂L₂ supercomplexes. Sheng et al. (2021) Plant Cell Physiol., 62:1108-1120.

Figure 3. Förster resonance energy transfer (FRET) networks of green algal and plant PSII-LHCII supercomplexes and major energy transfer pathways. Sheng et al. (2021) Plant Cell Physiol., 62:1108-1120.

II. Structural basis of LhcbM5-mediated state transitions in green algae.

In green algae and plants, state transitions serve as a short-term light-acclimation process in the regulation of the light-harvesting capacity of photosystems I and II (PSI and PSII, respectively). During the process, a portion of light-harvesting complex II (LHCII) is phosphorylated, dissociated from PSII and binds with PSI to form the supercomplex PSI–LHCI–LHCII. We reported high-resolution structures of PSI–LHCI–LHCII from Chlamydomonas reinhardtii, revealing the mechanism of assembly between the PSI–LHCI complex and two phosphorylated LHCII trimers containing all four types of LhcbM protein (Figure 4). Two specific LhcbM isoforms, namely LhcbM1 and LhcbM5, directly interact with the PSI core through their phosphorylated amino terminal regions. Furthermore, biochemical and functional studies on mutant strains lacking either LhcbM1 or LhcbM5 indicate that only LhcbM5 is indispensable in supercomplex formation. The results unravel the specific interactions and potential excitation energy transfer routes between green algal PSI and two phosphorylated LHCIIs (Pan et al., Nat. Plants, 7:1119-1131).

Figure 4. Surface representation of the CrPSI–LHCI–LHCII supercomplex from the pph1;pbcp mutant strain, with pThr residues from LhcbM1 and LhcbM5 highlighted in red. b, Detailed interaction between the N-terminal region of LhcbM1 and PSI core subunits PsaH and PsaL. c, Sequence alignment of the interaction-related regions of LhcbM1, PsaL and PsaH from C. reinhardtii (Cr) with Lhcb2, PsaL and PsaH from Zm, respectively. Conserved and variant residues involved in intersubunit interactions are indicated by blue and red asterisks, respectively. d, Structural comparison of N-terminal five residues (shown as sticks) of CrLhcbM1 (carbon atoms coloured green) and ZmLhcb2 (carbon atoms coloured white). The PSI core is shown in electrostatic surface mode with red and blue representing acidic and basic regions, respectively. e, Detailed interactions between the N-terminal region of LhcbM5 and the PSI core subunit PsaH. Hydrogen bond interactions are shown as black dashed lines. Pan et al. (2021) Nat. Plants, 7:1119-1131.

PhD Program

This division is currently recruiting graduate students.

Reports

Annual Report 2021（PDF）

Selected Publications

Kubota, M., Kim, E., Ishii, A., and Minagawa, J. (2024). The blue-green light-dependent state transition in the marine phytoplankton Ostreococcus tauri. New Phytol. 244, 1837-1846. https://doi.org/10.1111/nph.20137

Kosugi, M., Ohtani, S., Hara, K., Toyoda, A., Nishide, H., Ozawa, S.-I., Takahashi, Y., Kashino, Y., Kudoh, S., Koike, H., and Minagawa, J. (2024). Characterization of the far-red light absorbing light-harvesting chlorophyll a/b binding complex, a derivative of the distinctive Lhca gene family in green algae. Front. Plant Sci. 15, 1409116.

Ishii, A., Shan, J., Sheng, S., Kim, E., Watanabe, A., Yokono, M., Noda, C., Song, C., Murata, K., Liu, Z., and Minagawa, J. (2023). The photosystem I supercomplex from a primordial green alga Ostreococcus tauri harbors three light-harvesting complex trimers. eLife 12, e84488.

Pan, X., Tokutsu, R., Li, A., Takizawa, K., Song, C., Murata, K., Yamasaki, T., Liu, Z., Minagawa, J., and Li, M. (2022). Structural basis of LhcbM5-mediated state transitions in green algae. Nat. Plants 7, 1119-1131.

Kim, E., Watanabe, A., Duffy, C. D. P., Ruban, A. V., and Minagawa, J. (2020). Multimeric and monomeric photosystem II supercomplexes represent structural adaptations to low- and high-light conditions. J Biol. Chem. 295, 14537-14545.

Sheng, X., Watanabe, A., Li, A., Kim, E., Song, C., Murata, K., Song, D., Minagawa, J., and Liu, Z. (2019). Structural insight into light harvesting for photosystem II in green algae. Nat. Plants 5, 1320-1330.

Tokutsu, R., Fujimura-Kamada, K., Matsuo, T., Yamasaki, T., and Minagawa, J. (2019). The CONSTANS flowering complex controls the protective response of photosynthesis in the green alga Chlamydomonas. Nat. Commun. 10, 4099.

Aihara, Y., Fujimura-Kamada, K., Yamasaki, T., and Minagawa, J. (2019). Algal photoprotection is regulated by the E3 ligase CUL4-DDB1^DET1. Nat. Plants 5, 34-40.

Kosuge, K., Tokutsu, R., Kim, E., Akimoto, S., Yokono, M., Ueno, Y., and Minagawa, J. (2018). LHCSR1-dependent fluorescence quenching is mediated by excitation energy transfer from LHCII to photosystem I in Chlamydomonas reinhardtii. Proc. Natl. Acad. Sci. USA 115, 3722-3727.

Petroutsos, D., Tokutsu, R., Maruyama, S., Flori, S., Greiner, A., Magneschi, L., Cusant, L., Kottke, T., Mittag, M., Hegemann, P., Finazzi, G., and Minagawa, J. (2016). A blue light photoreceptor mediates the feedback regulation of photosynthesis. Nature 537, 563-566.

Tokutsu, R., and Minagawa, J. (2013). Energy-dissipative supercomplex of photosystem II associated with LHCSR3 in Chlamydomonas reinhardtii. Proc. Natl. Acad. Sci. USA 110, 10016-10021.

Iwai, M., Takizawa, K., Tokutsu, R., Okamuro, A., Takahashi, Y., and Minagawa, J. (2010). Isolation of the elusive supercomplex driving cyclic electron transfer in photosynthesis. Nature 464, 1210-1213.