Identification and Characterization of a Ferritin Gene and Its Product from the Multicellular Green AlgaUlva pertusa

Abstract

Iron is an essential element for virtually all kingdoms of life, and especially for primary producers in ocean ecosystems. To date, the molecular mechanism of iron utilization by macroalgae remains largely unknown. To elucidate the strategy of iron acquisition and storage in macroalgae, we focused on the function of the iron storage protein ferritin in the sea lettuce, Ulva pertusa, which has abundant iron content. Judging from the primary structure, U. pertusa ferritin (UpFer) can be classified as a land-plant-type ferritin, which is usually found in plastids. The gene of UpFer was expressed in the peripheral, central and rhizoid parts. Western blot analysis showed that UpFER was present and functioned in processed 26- and 22-kDa forms. Furthermore, recombinant UpFER had iron incorporation activity comparable to other ferritins. These results suggest that ferritin also functions as an iron storage protein as in unicellular algae and land plants.

The iron content and ferritin contribution in fresh, dried, and toasted nori, Pyropia yezoensis

“…In addition, iron content of raw nori was comparable with that of U. pertusa, which had highest iron content among coastal green, red, and brown macroalgae as we analyzed in the previous study. 24) Together with the good bioavailability of iron in red alga Porphyra sp. (a native species of Venezuela), 15,16) nori can be considered as a good nutritional iron source.…”

“…The cDNA sequence has been submitted to the NCBI database (GenBank ID: AB918149). The amino acid sequence of PyFer shows 38% and 35% sequence identity with ferritin, respectively, from U. pertusa 24,26) (green macroalga) and soybean ferritin subunit No. 4.…”

“…19,[38][39][40] On the other hand, ferritin contribution to iron storage in macroalgae or seaweeds is explored only recently, 24) although a ferritin gene is described as a stress-induced gene in a green seaweed Ulva sp. 41) Algae have developed sophisticated mechanisms for iron acquisition and storage, because onethird of the ocean is assumed to be deficient in iron due to its extremely low solubility in the oxidized state.…”

“…Recently, we showed that a green macroalga, Ulva pertusa, contains high amount of iron, and ferritin protein was detected in thalli of this alga. 24) It was the first report that demonstrates ferritin contribution for macroalgal iron storage. In the present study, we focused on iron in various forms and grades of nori, P. yezoensis.…”

Soybean Ferritin Forms an Iron-Containing Oligomer in Tofu Even after Heat Treatment

“…In tofu gel, ferritin maintained a similar oligomeric structure, which contained thousands of iron. We can presume that ferritin is present in various foods, including those of plant origin. , Despite such significant nutritional values, soybeans are not always regarded as an important staple food for humans worldwide. In addition to nutritional evaluations, further research on the utilization and development of soybean seeds as a substantial food material is needed.…”