Interaction of ascorbate with photosystem i

Boris V. Trubitsin, Mahir D. Mamedov, Alexey Yu Semenov, Alexander N. Tikhonov

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Ascorbate is one of the key participants of the antioxidant defense in plants. In this work, we have investigated the interaction of ascorbate with the chloroplast electron transport chain and isolated photosystem I (PSI), using the EPR method for monitoring the oxidized centers P+ P 700 + and ascorbate free radicals. Inhibitor analysis of the light-induced redox transients of P700 in spinach thylakoids has demonstrated that ascorbate efficiently donates electrons to P +700 via plastocyanin. Inhibitors (DCMU and stigmatellin), which block electron transport between photosystem II and Pc, did not disturb the ascorbate capacity for electron donation to P +700 . Otherwise, inactivation of Pc with CN- ions inhibited electron flow from ascorbate to P +700. This proves that the main route of electron flow from ascorbate to P +700 runs through Pc, bypassing the plastoquinone (PQ) pool and the cytochrome b 6 f complex. In contrast to Pc-mediated pathway, direct donation of electrons from ascorbate to P +700 is a rather slow process. Oxidized ascorbate species act as alternative oxidants for PSI, which intercept electrons directly from the terminal electron acceptors of PSI, thereby stimulating photooxidation of P700. We investigated the interaction of ascorbate with PSI complexes isolated from the wild type cells and the MenB deletion strain of cyanobacterium Synechocystis sp. PCC 6803. In the MenB mutant, PSI contains PQ in the quinone-binding A1-site, which can be substituted by high-potential electron carrier 2,3-dichloro-1,4-naphthoquinone (Cl2NQ). In PSI from the MenB mutant with Cl2NQ in the A1-site, the outflow of electrons from PSI is impeded due to the uphill electron transfer from A1 to the iron-sulfur cluster FX and further to the terminal clusters FA/FB, which manifests itself as a decrease in a steady-state level of P +700. The addition of ascorbate promoted photooxidation of P700 due to stimulation of electron outflow from PSI to oxidized ascorbate species. Thus, accepting electrons from PSI and donating them to P +700 +, ascorbate can mediate cyclic electron transport around PSI. The physiological significance of ascorbate-mediated electron transport is discussed.

Original languageEnglish
Pages (from-to)215-231
Number of pages17
JournalPhotosynthesis Research
Volume122
Issue number2
DOIs
Publication statusPublished - 2014
Externally publishedYes

Fingerprint

Photosystem I Protein Complex
photosystem I
electrons
Electrons
Electron Transport
electron transfer
Plastoquinone
photooxidation
Photooxidation
Cytochrome b6f Complex
plastocyanin
Plastocyanin
Synechocystis sp. PCC 6803
naphthoquinones
Diuron
mutants
Synechocystis
Thylakoids
electron transport chain
Photosystem II Protein Complex

Keywords

  • Ascorbate
  • Cyclic electron transport
  • Photosynthesis
  • Photosystem I

ASJC Scopus subject areas

  • Plant Science
  • Cell Biology
  • Biochemistry
  • Medicine(all)

Cite this

Interaction of ascorbate with photosystem i. / Trubitsin, Boris V.; Mamedov, Mahir D.; Semenov, Alexey Yu; Tikhonov, Alexander N.

In: Photosynthesis Research, Vol. 122, No. 2, 2014, p. 215-231.

Research output: Contribution to journalArticle

Trubitsin, BV, Mamedov, MD, Semenov, AY & Tikhonov, AN 2014, 'Interaction of ascorbate with photosystem i', Photosynthesis Research, vol. 122, no. 2, pp. 215-231. https://doi.org/10.1007/s11120-014-0023-7
Trubitsin, Boris V. ; Mamedov, Mahir D. ; Semenov, Alexey Yu ; Tikhonov, Alexander N. / Interaction of ascorbate with photosystem i. In: Photosynthesis Research. 2014 ; Vol. 122, No. 2. pp. 215-231.
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