Planta

, Volume 220, Issue 4, pp 572–581

Characterization of photosynthetic electron transport in bundle sheath cells of maize. I. Ascorbate effectively stimulates cyclic electron flow around PSI

  • Boris Ivanov
  • Kozi Asada
  • David M. Kramer
  • Gerald Edwards
Original Article

DOI: 10.1007/s00425-004-1367-6

Cite this article as:
Ivanov, B., Asada, K., Kramer, D.M. et al. Planta (2005) 220: 572. doi:10.1007/s00425-004-1367-6

Abstract

Redox changes of the reaction-center chlorophyll of photosystem I (P700) and chlorophyll fluorescence yield were measured in bundle sheath strands (BSS) isolated from maize (Zea mays L.) leaves. Oxidation of P700 in BSS by actinic light was suppressed by nigericin, indicating the generation of a proton gradient across the thylakoid membranes of BSS chloroplasts. Methyl viologen, which transfers electrons from photosystem I (PSI) to O2, caused a considerable decrease in the reduction rate of P700+ in BSS after turning off actinic light, showing that electron flow from the acceptor side of PSI to stromal components is critical for this reduction. Ascorbate (Asc), and to a lesser extent malate (Mal), caused a lower level of P700+ in BSS under aerobic conditions in far-red light, implying electron donation from these substances to the intersystem carriers. When Asc or Mal was added to BSS during pre-illumination under anaerobic conditions in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), the far-red-induced level of P700+ was lowered. The results suggest Asc and Mal can cause reduction of stromal donors, which in turn establishes conditions for rapid PSI-driven P700+ reduction. Addition of these metabolites also strongly stimulated the development of a proton gradient in thylakoids under aerobic conditions in the absence of DCMU, i.e. under conditions analogous to those in vivo. Ascorbate was a much more effective electron donor than Mal, suggesting it has a physiological role in activation of cyclic electron flow around PSI.

Keywords

Ascorbate Bundle sheath cells C4 photosynthesis Cyclic electron flow P700 Zea 

Abbreviations

Asc

Ascorbate

BS

Bundle sheath

BSS

Bundle sheath strands

Chl

Chlorophyll

CEF1

Cyclic electron flow around PSI

DBMIB

2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone

DCMU

3-(3,4-dichlorophenyl)-1,1-dimethyl urea

FR

Far-red light

Mal

Malate

MV

Methyl viologen (paraquat)

NADP-ME

NADP-malic enzyme

NDH

NAD(P)H dehydrogenase

PSI, PSII

Photosystem I, II

P700, P700+

Reduced and oxidized forms of reaction center chlorophyll of PSI

pmf

Proton-motive force

ΔpH

pH difference between the lumen and stroma

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Boris Ivanov
    • 2
  • Kozi Asada
    • 3
  • David M. Kramer
    • 4
  • Gerald Edwards
    • 1
  1. 1.School of Biological SciencesWashington State UniversityPullmanUSA
  2. 2.Institute of Basic Biological ProblemsRussian Academy of SciencesPushchinoRussia
  3. 3.Faculty of Life Science and BiotechnologyFukuyama UniversityFukuyamaJapan
  4. 4.Institute of Biological ChemistryWashington State UniversityPullmanUSA

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