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

Research output: Contribution to journalArticlepeer-review

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 S2QA. 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.

Original languageEnglish
Article number148509
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1863
Issue number1
DOIs
Publication statusPublished - Jan 1 2022

Keywords

  • Anabaena sp. PCC 7120
  • Heterocyst
  • PSII
  • Time-resolved fluorescence

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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