Present address: Department of Environment, Water, Heritage and Arts, King Edward Terrace, Parkes, ACT 2600, Australia.
DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON-REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE1
Article first published online: 21 MAY 2009
© 2009 Phycological Society of America
Journal of Phycology
Volume 45, Issue 3, pages 771–783, June 2009
How to Cite
Pankowski, A. and McMinn, A. (2009), DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON-REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE. Journal of Phycology, 45: 771–783. doi: 10.1111/j.1529-8817.2009.00687.x
Received 3 February 2008. Accepted 28 January 2009.
- Issue published online: 5 JUN 2009
- Article first published online: 21 MAY 2009
While the growth of Southern Ocean phytoplankton is often limited by iron availability, there are no comparable experiments on sea-ice algae. Here we assess the use of ferredoxin and flavodoxin to investigate the iron nutritional status of sea-ice algae and describe the development of a quantitative immunoassay for both proteins in marine diatoms. High-affinity monoclonal antibodies toward both proteins were produced from Cylindrotheca closterium (Ehrenb.) J. M. Lewin et Reimann, and these were used to develop Western blots. Western blots run on whole protein extracts detected both proteins with little cross-reactivity toward other proteins. The two proteins could be successfully quantitated when applied to gels at between 5 and 50 ng in a volume of 25 μL (0.2–2 μg · mL−1). Flavodoxin and ferrodoxin expression was examined in the Antarctic diatoms Entomoneis kjellmannii (Cleve) Poulin et Cardinal, Navicula directa (W. Sm.) Ralfs, Fragilariopsis curta (Van Heurck) Hust., Pseudo-nitzschia sp., Porosira glacialis (Grunow) E. G. Jørg., Fragilariopsis cylindrus (Grunow) Willi Krieg., Fragilariopsis sublinearis (Van Heurck) Heiden et Kolbe, C. closterium, Nitzschia lecointei Van Heurck, and the dinoflagellate Polarella glacialis Montresor, Procaccini et Stoecker. Two Arctic isolates were also examined, Nitzschia frigida (Grunow) and Fragilariopsis oceanica (Cleve) Hasle. Significant heterogeneity of protein expression was observed despite all cultures being grown in iron-replete f/2 medium. Only one species, F. cylindrus, displayed the expected expression of ferredoxin only in iron-replete medium. Four were observed to produce both proteins under iron-replete conditions. Ferredoxin was not detected at all in F. curta and Pseudo-nitzschia sp., but distinct flavodoxin bands were observed in both of these organisms. All species examined were observed to express either flavodoxin or ferredoxin or both of the proteins as determined by Western immunoblotting.