Alteration of proteins and pigments influence the function of photosystem i under iron deficiency from chlamydomonas reinhardtii

Venkateswarlu Yadavalli, Craig C. Jolley, Chandramouli Malleda, Balakumar Thangaraj, Petra Fromme, Rajagopal Subramanyam

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Background: Iron is an essential micronutrient for all organisms because it is a component of enzyme cofactors that catalyze redox reactions in fundamental metabolic processes. Even though iron is abundant on earth, it is often present in the insoluble ferric [Fe (III)] state, leaving many surface environments Fe-limited. The haploid green alga Chlamydomonas reinhardtii is used as a model organism for studying eukaryotic photosynthesis. This study explores structural and functional changes in PSI-LHCI supercomplexes under Fe deficiency as the eukaryotic photosynthetic apparatus adapts to Fe deficiency. Results: 77K emission spectra and sucrose density gradient data show that PSI and LHCI subunits are affected under iron deficiency conditions. The visible circular dichroism (CD) spectra associated with strongly-coupled chlorophyll dimers increases in intensity. The change in CD signals of pigments originates from the modification of interactions between pigment molecules. Evidence from sucrose gradients and non-denaturing (green) gels indicates that PSI-LHCI levels were reduced after cells were grown for 72 h in Fe-deficient medium. Ultrafast fluorescence spectroscopy suggests that red-shifted pigments in the PSI-LHCI antenna were lost during Fe stress. Further, denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI subunits PsaC and PsaD decreased, while PsaE was completely absent after Fe stress. The light harvesting complexes were also susceptible to iron deficiency, with Lhca1 and Lhca9 showing the most dramatic decreases. These changes in the number and composition of PSI-LHCI supercomplexes may be caused by reactive oxygen species, which increase under Fe deficiency conditions. Conclusions: Fe deficiency induces rapid reduction of the levels of photosynthetic pigments due to a decrease in chlorophyll synthesis. Chlorophyll is important not only as a light-harvesting pigment, but also has a structural role, particularly in the pigment-rich LHCI subunits. The reduced level of chlorophyll molecules inhibits the formation of large PSI-LHCI supercomplexes, further decreasing the photosynthetic efficiency.

Original languageEnglish
Article numbere35084
JournalPLoS One
Volume7
Issue number4
DOIs
Publication statusPublished - Apr 13 2012

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Chlamydomonas reinhardtii
Chlorophyll
Pigments
Iron
pigments
iron
Circular Dichroism
circular dichroism spectroscopy
Sucrose
chlorophyll
Proteins
proteins
Gels
Dichroism
Light
Chlorophyta
Micronutrients
Haploidy
Fluorescence Spectrometry
Coenzymes

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Alteration of proteins and pigments influence the function of photosystem i under iron deficiency from chlamydomonas reinhardtii. / Yadavalli, Venkateswarlu; Jolley, Craig C.; Malleda, Chandramouli; Thangaraj, Balakumar; Fromme, Petra; Subramanyam, Rajagopal.

In: PLoS One, Vol. 7, No. 4, e35084, 13.04.2012.

Research output: Contribution to journalArticle

Yadavalli, Venkateswarlu ; Jolley, Craig C. ; Malleda, Chandramouli ; Thangaraj, Balakumar ; Fromme, Petra ; Subramanyam, Rajagopal. / Alteration of proteins and pigments influence the function of photosystem i under iron deficiency from chlamydomonas reinhardtii. In: PLoS One. 2012 ; Vol. 7, No. 4.
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AU - Thangaraj, Balakumar

AU - Fromme, Petra

AU - Subramanyam, Rajagopal

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