Abstract
Flavodoxin is a small electron-transfer protein capable of replacing ferredoxin during periods of Fe deficiency. When evaluating the suitability of flavodoxin as a diagnostic indicator for Fe limitation of phytoplankton growth, we examined its expression in two marine diatoms we cultured using trace-metal-buffered medium. Thalassio-sira weissflogii and Phaeodactylum tricornutum were cultured in ethylenediaminetetraacetic acid-buffered Sargasso Sea water containing from 10 to 1000 nM added Fe. Trace-metal-buffered cultures of each diatom maintained high growth rates across the entire range of Fe additions. Similarly, declines in chlorophyll/cell and in the ratio of photosystem II variable-to-maximum fluorescence were negligible (P. tricornutum) to moderate (T. weissflogii; 54% decline in chlorophyll/cell and 22% decrease in variable-to-maximum fluorescence). Moreover, only minor variations in photosynthetic parameters were observed across the range of additions. In contrast, flavodoxin was expressed to high levels in low-Fe cultures. Despite the inverse relationship between flavodoxin expression and Fe content of the medium, its expression was seemingly independent of any of the indicators of cell physiology that were assayed. It appears that flavodoxin is expressed as an early-stage response to Fe stress and that its accumulation need not be intimately connected to limitations imposed by Fe on the growth rate of these diatoms.
Full Text
The Full Text of this article is available as a PDF (1.8 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Butler W. L., Kitajima M. Fluorescence quenching in photosystem II of chloroplasts. Biochim Biophys Acta. 1975 Jan 31;376(1):116–125. doi: 10.1016/0005-2728(75)90210-8. [DOI] [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]
- 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]
- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Rabilloud T., Carpentier G., Tarroux P. Improvement and simplification of low-background silver staining of proteins by using sodium dithionite. Electrophoresis. 1988 Jun;9(6):288–291. doi: 10.1002/elps.1150090608. [DOI] [PubMed] [Google Scholar]
- Sandmann G., Malkin R. Iron-sulfur centers and activities of the photosynthetic electron transport chain in iron-deficient cultures of the blue-green alga aphanocapsa. Plant Physiol. 1983 Nov;73(3):724–728. doi: 10.1104/pp.73.3.724. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Scanlan D. J., Mann N. H., Carr N. G. The response of the picoplanktonic marine cyanobacterium Synechococcus species WH7803 to phosphate starvation involves a protein homologous to the periplasmic phosphate-binding protein of Escherichia coli. Mol Microbiol. 1993 Oct;10(1):181–191. doi: 10.1111/j.1365-2958.1993.tb00914.x. [DOI] [PubMed] [Google Scholar]
- Towbin H., Staehelin T., Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350–4354. doi: 10.1073/pnas.76.9.4350. [DOI] [PMC free article] [PubMed] [Google Scholar]