Iron-Induced Changes in Light Harvesting and Photochemical Energy Conversion Processes in Eukaryotic Marine Algae 1
Richard M Greene
Richard J Geider
Zbigniew Kolber
Paul G Falkowski
Supported by the U.S. Department of Energy under contract No. DE-AC02-76CH00016, the National Science Foundation grant No. OCE8915084 (to R.J.G.), National Aeronautics and Space Administration grant UPN 161-35-05-08 (to P.G.F.), and the Environmental Protection Agency grant No. DW89935239-01-0 (to P.G.F.).
Abstract
The role of iron in regulating light harvesting and photochemical energy conversion processes was examined in the marine unicellular chlorophyte Dunaliella tertiolecta and the marine diatom Phaeodactylum tricornutum. In both species, iron limitation led to a reduction in cellular chlorophyll concentrations, but an increase in the in vivo, chlorophyll-specific, optical absorption cross-sections. Moreover, the absorption cross-section of photosystem II, a measure of the photon target area of the traps, was higher in iron-limited cells and decreased rapidly following iron addition. Iron-limited cells exhibited reduced variable/maximum fluorescence ratios and a reduced fluorescence per unit absorption at all wave-lengths between 400 and 575 nm. Following iron addition, variable/maximum fluorescence ratios increased rapidly, reaching 90% of the maximum within 18 to 25 h. Thus, although more light was absorbed per unit of chlorophyll, iron limitation reduced the transfer efficiency of excitation energy in photosystem II. The half-time for the oxidation of primary electron acceptor of photosystem II, calculated from the kinetics of decay of variable maximum fluorescence, increased 2-fold under iron limitation. Quantitative analysis of western blots revealed that cytochrome f and subunit IV (the plastoquinone-docking protein) of the cytochrome b6/f complex were also significantly reduced by lack of iron; recovery from iron limitation was completely inhibited by either cycloheximide or chloramphenicol. The recovery of maximum photosynthetic energy conversion efficiency occurs in three stages: (a) a rapid (3-5 h) increase in electron transfer rates on the acceptor side of photosystem II correlated with de novo synthesis of the cytochrome b6/f complex; (b) an increase (10-15 h) in the quantum efficiency correlated with an increase in D1 accumulation; and (c) a slow (>18 h) increase in chlorophyll levels accompanied by an increase in the efficiency of energy transfer from the light-harvesting chlorophyll proteins to the reaction centers.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bruce B. D., Malkin R. Biosynthesis of the chloroplast cytochrome b6f complex: studies in a photosynthetic mutant of Lemna. Plant Cell. 1991 Feb;3(2):203–212. doi: 10.1105/tpc.3.2.203. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Debus R. J., Feher G., Okamura M. Y. Iron-depleted reaction centers from Rhodopseudomonas sphaeroides R-26.1: characterization and reconstitution with Fe2+, Mn2+, Co2+, Ni2+, Cu2+, and Zn2+. Biochemistry. 1986 Apr 22;25(8):2276–2287. doi: 10.1021/bi00356a064. [DOI] [PubMed] [Google Scholar]
- Doyle M. P., Li L. B., Yu L., Yu C. A. Identification of a Mr = 17,000 protein as the plastoquinone-binding protein in the cytochrome b6-f complex from spinach chloroplasts. J Biol Chem. 1989 Jan 25;264(3):1387–1392. [PubMed] [Google Scholar]
- GUILLARD R. R., RYTHER J. H. Studies of marine planktonic diatoms. I. Cyclotella nana Hustedt, and Detonula confervacea (cleve) Gran. Can J Microbiol. 1962 Apr;8:229–239. doi: 10.1139/m62-029. [DOI] [PubMed] [Google Scholar]
- Kirmaier C., Holten D., Debus R. J., Feher G., Okamura M. Y. Primary photochemistry of iron-depleted and zinc-reconstituted reaction centers from Rhodopseudomonas sphaeroides. Proc Natl Acad Sci U S A. 1986 Sep;83(17):6407–6411. doi: 10.1073/pnas.83.17.6407. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kitajima M., Butler W. L. Quenching of chlorophyll fluorescence and primary photochemistry in chloroplasts by dibromothymoquinone. Biochim Biophys Acta. 1975 Jan 31;376(1):105–115. doi: 10.1016/0005-2728(75)90209-1. [DOI] [PubMed] [Google Scholar]
- Kolber Z., Zehr J., Falkowski P. Effects of Growth Irradiance and Nitrogen Limitation on Photosynthetic Energy Conversion in Photosystem II. Plant Physiol. 1988 Nov;88(3):923–929. doi: 10.1104/pp.88.3.923. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Morales F., Abadía A., Abadía J. Chlorophyll Fluorescence and Photon Yield of Oxygen Evolution in Iron-Deficient Sugar Beet (Beta vulgaris L.) Leaves. Plant Physiol. 1991 Nov;97(3):886–893. doi: 10.1104/pp.97.3.886. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ohad I., Kyle D. J., Arntzen C. J. Membrane protein damage and repair: removal and replacement of inactivated 32-kilodalton polypeptides in chloroplast membranes. J Cell Biol. 1984 Aug;99(2):481–485. doi: 10.1083/jcb.99.2.481. [DOI] [PMC free article] [PubMed] [Google Scholar]