Excitation-energy transfer in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120 as studied by time-resolved fluorescence spectroscopy

Ryo Nagao; Makio Yokono; Yoshifumi Ueno; Yoshiki Nakajima; Takehiro Suzuki; Ka-Ho Kato; Naoki Tsuboshita; Naoshi Dohmae; Jian-Ren Shen; Shigeki Ehira; Seiji Akimoto

doi:10.1016/j.bbabio.2021.148509

Excitation-energy transfer in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120 as studied by time-resolved fluorescence spectroscopy

Biochim Biophys Acta Bioenerg. 2022 Jan 1;1863(1):148509. doi: 10.1016/j.bbabio.2021.148509. Epub 2021 Nov 15.

Authors

Ryo Nagao¹, Makio Yokono², Yoshifumi Ueno³, Yoshiki Nakajima⁴, Takehiro Suzuki⁵, Ka-Ho Kato⁴, Naoki Tsuboshita⁴, Naoshi Dohmae⁵, Jian-Ren Shen⁴, Shigeki Ehira⁶, Seiji Akimoto⁷

Affiliations

¹ Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan. Electronic address: nagaoryo@okayama-u.ac.jp.
² Institute of Low Temperature Science, Hokkaido University, Hokkaido 060-0819, Japan.
³ Graduate School of Science, Kobe University, Hyogo 657-8501, Japan.
⁴ Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
⁵ Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan.
⁶ Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Tokyo 192-0397, Japan. Electronic address: ehira@tmu.ac.jp.
⁷ Graduate School of Science, Kobe University, Hyogo 657-8501, Japan. Electronic address: akimoto@hawk.kobe-u.ac.jp.

PMID: 34793768
DOI: 10.1016/j.bbabio.2021.148509

Abstract

Heterocysts are formed in filamentous heterocystous cyanobacteria under nitrogen-starvation conditions, and possess a very low amount of photosystem II (PSII) complexes than vegetative cells. Molecular, morphological, and biochemical characterizations of heterocysts have been investigated; however, excitation-energy dynamics in heterocysts are still unknown. In this study, we examined excitation-energy-relaxation processes of pigment-protein complexes in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120. Thylakoid membranes from the heterocysts showed no oxygen-evolving activity under our experimental conditions and no thermoluminescence-glow curve originating from charge recombination of S₂Q_A^-. Two dimensional blue-native/SDS-PAGE analysis exhibits tetrameric, dimeric, and monomeric photosystem I (PSI) complexes but almost no dimeric and monomeric PSII complexes in the heterocyst thylakoids. The steady-state fluorescence spectrum of the heterocyst thylakoids at 77 K displays both characteristic PSI fluorescence and unusual PSII fluorescence different from the fluorescence of PSII dimer and monomer complexes. Time-resolved fluorescence spectra at 77 K, followed by fluorescence decay-associated spectra, showed different PSII and PSI fluorescence bands between heterocysts and vegetative thylakoids. Based on these findings, we discuss excitation-energy-transfer mechanisms in the heterocysts.

Keywords: Anabaena sp. PCC 7120; Heterocyst; PSII; Time-resolved fluorescence.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anabaena
Cyanobacteria*
Energy Transfer
Photosystem II Protein Complex

Substances

Photosystem II Protein Complex