Differences between two green algae in biological availability of iron bound to strong chelators

• Published in: Botany Vol. 84; no. 3; pp. 400 - 411
• Main Authors: Weger, H.G, Matz, C.J, Magnus, R.S, Walker, C.N, Fink, M.B, Treble, R.G
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.03.2006; Canadian Science Publishing NRC Research Press
• Subjects: Algae; algae and seaweeds; Aquatic plants; Bioavailability; Botany; Chelates; Chelating agents; chelators; Chlamydomonas; Chlamydomonas reinhardtii; Chlorella; Chlorella kessleri; Chlorella réductase ferrique; chélateurs; Differences; ferric reductase; ferric reduction; Green algae; HBED; Iron; iron limitation; limitation par le fer; nutrient availability; Nutritional aspects; oxidoreductases; Physiological aspects; plant nutrition; plants; Plasma; reduction; réduction ferrique; schizokinen; schizokinien; Strategy I; Stratégie I
• ISSN: 0008-4026; 1916-2790; 1480-3305; 1916-2804
• DOI: 10.1139/B06-013

N,N′-di(2-hydroxybenzoyl)-ethylenediamine-N,N′-diacetic acid (HBED) is a very strong Fe 3+ chelator. Strategy I vascular plants, which use a reductive system for iron acquisition, similar to many green algae, are able to access iron from HBED (R.L. Chaney. 1988. J. Plant Nutr. 11: 1033-1050). However, iron-limited cells of the Strategy I green alga Chlamydomonas reinhardtii Dangeard were unable to access iron present as Fe 3+ -HBED. In contrast, Fe 3+ chelated with hydroxyethylethylenediaminetriacetic acid (HEDTA; a weaker chelator) was rapidly taken up by iron-limited Chlamydomonas cells. Chlamydomonas ferric reduction rates with Fe 3+ -HBED were approximately 15% of the rate observed with Fe 3+ -HEDTA, suggesting that low reduction rates with Fe 3+ -HBED might be one factor in the low rate of iron acquisition. By contrast, iron-limited cells of the Strategy I green alga Chlorella kessleri Fott et Nováková were able to rapidly assimilate Fe 3+ chelated by HBED, although ferric reduction rates with Fe 3+ -HBED were approximately 38% the rate of activity with Fe 3+ -HEDTA. Similar differential iron uptake rates for the two algal species were obtained using the strong Fe 3+ chelator (and siderophore analogue) desferrioxamine B mesylate and the cyanobacterial siderophore schizokinen. These results suggest that there are differences among Strategy I green algae in their abilities to acquire Fe 3+ from various ferric chelates: not all Strategy I algae can equally access tightly complexed Fe 3+ . Chlamydomonas appears to be the first documented Strategy I organism that is unable to acquire iron from Fe 3+ -HBED. These results also suggest that green algal iron acquisition from siderophores is species dependent. Finally, we suggest that iron acquisition from Fe 3+ -HBED might serve as an assay for an organisms' ability to access tightly complexed iron.